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In-Depth From A.D.A.M. Background

Pneumonia is an inflammation of the lung that is most often caused by infection with bacteria, viruses, or other organisms. Occasionally, inhaled chemicals that irritate the lungs can cause pneumonia. Healthy people can usually fight off pneumonia infections. However, people who are sick, including those who are recovering from the flu (influenza) or an upper respiratory illness, have weakened immune systems that make it easier for bacteria to grow in their lungs.

When air is inhaled through the nose or mouth, it travels down the trachea to the bronchus, where it first enters the lung. From the bronchus, air goes through the bronchi, into the even smaller bronchioles and lastly into the alveoli.

Defining Pneumonia by Location in the Lung

Pneumonia may be defined according to its location in the lung:

  • Lobar pneumonia occurs in one part, or lobe, of the lung.
  • Bronchopneumonia tends to be scattered throughout the lung.

Defining Pneumonia by Origin of Infection

Doctors often classify pneumonia based on where the disease is contracted. This helps predict which organisms are most likely responsible for the illness and, therefore, which treatment is most likely to be effective.

Community-Acquired Pneumonia (CAP). People with this type of pneumonia contracted the infection outside a hospital setting. It is one of the most common infectious diseases. It often follows a viral respiratory infection, such as the flu.

One of the most common causes of bacterial CAP is Streptococcus pneumoniae. Other causes include Haemophilus influenzae, mycoplasma, and Chlamydia.

Pneumonia Arising in an Institutional Setting

  • Hospital-Acquired Pneumonia. Hospital-acquired pneumonia is an infection of the lungs contracted during a hospital stay. This type of pneumonia tends to be more serious, because hospital patients already have weakened defense mechanisms, and the infecting organisms are usually more dangerous than those encountered in the community. Hospital patients are particularly vulnerable to Gram-negative bacteria and staphylococci. Hospital-acquired pneumonia is also called nosocomial pneumonia.
  • Ventilator-associated pneumonia (VAPP). A subgroup of hospital-acquired pneumonia is ventilator-associated pneumonia (VAP), a highly lethal form contracted by patients on ventilators in hospitals and long-term nursing facilities.
  • Pneumonia acquired in a nursing home or other long-term care facility.

Disease Process Leading to Pneumonia

Pneumonia-causing agents reach the lungs through different routes:

  • In most cases, a person breathes in the infectious organism, which then travels through the airways to the lungs.
  • Sometimes, the normally harmless bacteria in the mouth, or on items placed in the mouth, can enter the lungs. This usually happens if the body's "gag reflex," an extreme throat contraction that keeps substances out of the lungs, is not working properly.
  • Infections can spread through the bloodstream from other organs to the lungs.

However, in normal situations, the airways protect the lungs from substances that can cause infection.

  • The nose filters out large particles.
  • If smaller particles pass through, sensors along the airway prompt a cough or sneeze. This forces many particles back out of the body.
  • Tiny particles that reach the small tubes in the lungs (bronchioles) are trapped in a thick, sticky substance called mucus. The mucus and particles are pushed up and out of the lungs by tiny hair-like cells called cilia, which beat like a drum. This action is called the "mucociliary escalator."
  • If bacteria or other infectious organisms manage to avoid the airway's defenses, the body's immune system attacks them. Large white blood cells called macrophages destroy the foreign particles.

The above-mentioned defense systems normally keep the lung healthy. If these defenses are weakened or damaged, however, bacteria, viruses, fungi, and parasites can easily infect the lung, producing pneumonia.

The Lungs

The lungs are two spongy organs in the chest surrounded by a thin, moist membrane called the pleura. Each lung is composed of smooth, shiny lobes; the right lung has three lobes and the left has two. About 90% of the lung is filled with air. Only 10% is solid tissue. There are several parts to each lung.

When a person takes a breath (inhales), air travels from the windpipe (trachea) into the lung through the main bronchus, which branches into tiny flexible tubes called bronchi.

The bronchi divide, like the branches of a tree, into smaller airways called bronchioles.

The bronchioles lead to a group of microscopic sacs called alveoli, which look like clusters of grapes. Each healthy adult lung contains millions of tiny alveoli. (Note: The singular of alveoli is alveolus.)

Each alveolus has a thin membrane that allows oxygen and carbon dioxide to pass in and out of the capillaries, the smallest of the blood vessels. When you take a deep breath, the membrane unfolds and expands. Fresh oxygen moves into the capillaries, and carbon dioxide passes from the capillaries into the bloodstream, where it is carried out of the body through the lungs.

Blood vessels carry the oxygen-rich blood to the heart, where it is pumped throughout the body.

In-Depth From A.D.A.M. Causes

Bacteria are the most common cause of pneumonia. However, pneumonia can also be caused by viruses, fungi, and other agents. It is often impossible to identify the specific culprit.

Many bacteria are grouped into one of two large categories by the laboratory procedure used to look at them under a microscope. The procedure is known as Gram staining. Bacteria are stained with special dyes, then washed in a special solution. The color of the bacteria after washing determines whether they are Gram-negative or Gram-positive. Knowing which group the bacteria belong to helps determine the severity of the disease, and how to treat it. Different bacteria are treated with different drugs.

Gram-Positive Bacteria. These bacteria appear blue on the stain and are the most common organisms that cause pneumonia. They include:

  • Streptococcus (S.) pneumoniae (also called pneumococcus), the most common cause of pneumonia. This Gram-positive bacterium causes 20 - 60% of all community-acquired bacterial pneumonia (CAP) in adults. Studies also suggest it causes 13 - 38% of CAP in children.
  • Staphylococcus (S.) aureus, the other major Gram-positive bacterium responsible for pneumonia, causes about 2% of CAP and 10 - 15% of hospital-acquired pneumonias. It is the organism most often associated with viral influenza, and can develop about 5 days after the onset of flu symptoms. Pneumonia from S. aureus most often occurs in people with weakened immune systems, very young children, hospitalized patients, and drug abusers who use needles. It is uncommon in healthy adults.
  • Streptococcus pyogenes or Group A streptococcus.

Gram-Negative Bacteria. These bacteria stain pink. Gram-negative bacteria commonly cause infections in hospitalized or nursing home patients, children with cystic fibrosis, and people with chronic lung conditions.

  • Haemophilus (H.) influenzae is the second most common organism causing community-acquired pneumonia, accounting for 3 - 10% of all cases. It generally occurs in patients with chronic lung disease, older people, and alcoholics.
  • Klebsiella (K.) pneumoniae may be responsible for pneumonia in alcoholics and other people who are physically debilitated. It is also associated with recent use of potent antibiotics.
  • Pseudomonas (P.) aeruginosa is a major cause of hospital-acquired pneumonia (nosocomial pneumonia). It is a common cause of pneumonia in patients with chronic or severe lung disease.
  • Moraxella (M.) catarrhalis is found in everyone's nose and mouth. Experts have identified this bacterium as an uncommon cause of certain pneumonias, particularly in people with lung problems such as asthma or emphysema.
  • Neisseria (N.) meningitidis is one of the most common causes of meningitis (central nervous system infection), but the organism has been reported in pneumonia, particularly in epidemics of military recruits.
  • Other Gram-negative bacteria that cause pneumonia include E. coli, proteus (found in damaged lung tissue), enterobacter, and acetinobacter.

Atypical Pneumonia

Atypical pneumonias produce mild symptoms and a dry cough. Organisms that cause atypical pneumonias include:

  • Mycoplasma (M.) pneumoniae, the most common atypical pneumonia organism. Mycoplasma is a very small bacterium that lacks a cell wall. Pneumonia caused by M. pneumoniae spreads when someone carrying the infection comes in close contact with others for a long period of time. It is most often found in school-aged children and young adults. The condition, commonly called "walking pneumonia," is usually mild.
  • Chlamydia (C.) pneumoniae is now thought to cause 10% of all CAP cases. This atypical pneumonia is most common in young adults and children, and is usually mild. It is less common, but usually more severe, in the elderly.
  • Legionella pneumophila causes Legionnaires' disease. It is contracted by breathing in drops of contaminated water. Outbreaks are often reported in hotels, cruise ships, and office buildings, where people are exposed to contaminated droplets from cooling towers and evaporative condensers. They have also been reported in people who have been near whirlpools and saunas. Legionella pneumophila is not passed from person to person. Some experts believe the organism causes 29 - 47% of all pneumonia cases.

Legionnaires' disease was first described in 1976 after an outbreak of fatal pneumonia at an American Legion convention. The newly described organism that caused the disease was named Legionella pneumophila, shown in this picture. (Courtesy of the Centers for Disease Control.)

Viral Pneumonia

A number of viruses can cause pneumonia, either directly or indirectly. They include:

  • Influenza (Flu). Pneumonia is a major complication of the flu and can be very serious. Influenza-associated pneumonia is particularly risky for the elderly and people with underlying heart disease. It can develop about 5 days after flu symptoms start. The flu weakens the body's defense systems, making it easier for bacteria to grow in the lungs.
  • Respiratory syncytial virus (RSV). Most infants are infected with RSV at some point, but it is most often mild. However, RSV is a major cause of pneumonia in infants, as well as adults with damaged immune systems. Studies indicate that RSV pneumonia may be more common in adults, especially the elderly, than previously thought.
  • Severe acute respiratory syndrome (SARS). SARS is a respiratory infection caused by a newly-described coronavirus, which appears to have jumped from animals to humans. The disease was first reported in China in 2003.
  • Human parainfluenza virus. This virus is a leading cause of pneumonia and bronchitis in children, the elderly, and patients with damaged immune systems.
  • Adenoviruses. Adenoviruses are common and usually are not problematic, although they have been linked to about 10% of childhood pneumonias. Adenovirus 14 has been linked to an outbreak of severe community-acquired pneumonia in the Pacific northwest.
  • Herpes viruses. In adults, herpes simplex virus and varicella zoster (the cause of chickenpox) can cause pneumonia in people with impaired immune systems.
  • Avian influenza. Type A influenza subtype H5N1 in birds is spreading around the globe. Fortunately, only a few hundred human cases have been identified. Most have resulted from close contact with infected birds. Person-to-person contact is rare. All patients diagnosed with "bird flu" show signs of pneumonia, although symptoms may be mild. Oseltamivir (Tamiflu) is the most effective treatment for this type of influenza, which can be fatal.

Aspiration Pneumonia and Anaerobic Bacteria

The mouth contains a mixture of bacteria that is normally harmless. However, if this mixture reaches the lungs, it can cause a serious condition called aspiration pneumonia. This may happen after a head injury or general anesthesia, or when a patient takes drugs or alcohol. In such cases, the gag reflex doesn't work as well as it should, so bacteria can enter the airways. Unlike other organisms that are inhaled, bacteria that cause aspiration pneumonia do not need oxygen to live. These bacteria are called anaerobic bacteria.

Opportunistic Pneumonia

Impaired immunity leaves patients vulnerable to serious, life-threatening pneumonias known as opportunistic pneumonias. They are caused by organisms that are harmless to people with healthy immune systems. Infecting organisms include:

  • Pneumocystis carinii, renamed Pneumocystis jiroveci in 2002, is an atypical organism. Originally thought to be protozoa, it is now classified as a fungus. P. jiroveci is very common and generally harmless in people with healthy immune systems. It is the most common cause of pneumonia in AIDS patients.
  • Fungi, such as Mycobacterium avium
  • Viruses, such as cytomegalovirus (CMV)

In addition to AIDS, other conditions put patients at risk for opportunistic pneumonia. They include cancers, such as lymphoma and leukemia. Long-term use of corticosteroids and drugs known as immunosuppressants also increases the risk for these pneumonias.

Occupational and Regional Pneumonias

Exposure to chemicals can also cause inflammation and pneumonia. Where you work and live can put you at higher risk for exposure to pneumonia-causing organisms.

  • Workers exposed to cattle, pigs, sheep, and horses are at risk for pneumonia caused by anthrax, brucella, and Coxiella burnetii (which causes Q fever).
  • Agricultural and construction workers in the Southwest are at risk for coccidoidomycosis (Valley fever). The disease is caused by the spores of the fungus Coccidioides immitis.
  • Those working in Ohio and the Mississippi Valley are at risk for histoplasmosis, a lung disease caused by the fungus Histoplasma capsulatum.
  • Workers exposed to pigeons, parrots, parakeets, and turkeys are at risk for psittacosis, a lung disease caused by the bacteria Chlamydia psittaci.
  • Hantavirus, a rare virus carried by rodents, causes a dangerous form of lung disease. It does not spread from person to person. Cases have occurred in New Mexico, Arizona, California, Washington, and Mexico.

Severe Acute Respiratory Syndrome (SARS)

Severe acute respiratory syndrome (SARS) is a contagious respiratory infection that was recognized as a worldwide threat in 2003. The World Health Organization (WHO) officially identified SARS as a global health threat, and issued an unprecedented travel advisory. It wasn't clear at the time whether SARS would become a global pandemic or settle into a less aggressive pattern. The latter seems to have happened.

As of May 2005, there was no known SARS transmission anywhere in the world, according to the U.S. Centers for Disease Control and Prevention (CDC). The SARS outbreak is a dramatic example of how quickly world travel can spread a disease. According to reports from the CDC and WHO, more than 8,000 people became sick with SARS during the outbreak. Of that group, 774 died. The outbreak is also an example of how quickly a networked health monitoring system can respond to an emerging threat.

Causes And Risk Factors. SARS is a serious form of atypical pneumonia that causes acute respiratory distress and sometimes death. It is caused by a new member of the coronavirus family (the family that includes the virus that causes the common cold). The discovery of the SARS-related virus represents one of the fastest identifications of a new organism in history.

SARS is spread by droplet contact. When someone with SARS coughs or sneezes, infected droplets are sprayed into the air. Like other coronaviruses, the SARS virus may live on hands, tissues, and other surfaces for up to 6 hours in these droplets and up to 3 hours after the droplets have dried.

While droplet transmission through close contact has been responsible for most cases of SARS, there is evidence that SARS might also spread by infected droplets carried on hands and other objects the droplets touch. Airborne transmission was a real possibility in some cases. Live virus had even been found in the stool of people with SARS, where it has been shown to survive for up to 4 days. And the virus may be able to live for months or years when the temperature is below freezing.

The estimated incubation period is 2 - 10 days, although there have been documented cases where the onset of illness was considerably faster or slower. People with active symptoms of illness are clearly contagious. It is not known, however, how early people begin to be contagious before symptoms appear, or how long they might be contagious after the symptoms have disappeared.

Prevention. The best way to prevent SARS is to avoid direct contact with people who have SARS until 10 days after their fever and other symptoms are gone. Reduce travel to locations where there is an uncontrolled SARS outbreak. The CDC has identified hand hygiene as the cornerstone of SARS prevention. Wash your hands often with soap and water, or use an alcohol-based instant hand sanitizer. Cover your mouth and nose when sneezing or coughing. Consider respiratory secretions infectious. Clean commonly touched surfaces with an EPA-approved disinfectant. In some situations, masks, and goggles may help prevent the spread of airborne or droplet infection. Wear gloves when handling potentially infectious secretions.

Vaccine. In December 2004, the U.S. National Institutes of Health began a small clinical trial to test a preventive SARS vaccine. Interim results showed the vaccine to be safe and well tolerated. Chinese researchers began testing a SARS vaccine in May 2004.

Prognosis. The overall worldwide death rate due to SARS at the end of the outbreaks was 14 - 15%, although it was up to 50% in infected people over age 65. Many more were sick enough to require breathing assistance from a machine (mechanical ventilation). Others needed ICU care.

Today, intensive public health policies are proving to be effective in controlling outbreaks. Many nations have stopped the epidemic within their own countries. All nations must be vigilant, however, to keep this disease under control.


  • Heart failure
  • Liver failure
  • Myelodysplastic syndromes (bone marrow abnormalities leading to anemia, low platelet counts, and low white blood cell counts)
  • Respiratory failure

In-Depth From A.D.A.M. Symptoms

General Symptoms. The symptoms of bacterial pneumonia develop very quickly and typically include:

  • A single episode of shaking chills followed by fever
  • Chest pain on the side of the infected lung. Severe abdominal pain sometimes occurs in people with pneumonia in the lower lobes of the lung
  • Cough, which may be dry at first, but eventually produces sputum
  • Nausea, vomiting, and muscle aches
  • Rapid breathing and heartbeat
  • Shortness of breath

Emergency Symptoms. Symptoms of pneumonia indicating a medical emergency include the following:

  • Blood in sputum
  • Bluish-toned (cyanotic) skin
  • High fever
  • Labored and heavy breathing
  • Mental confusion or reduced mental function in the elderly
  • Rapid heart rate
  • Weight loss

Symptoms in the Elderly. It is important to note that older people may have fewer or different symptoms than younger people. Symptoms may come on much more slowly. An elderly person who experiences even a minor cough and weakness for more than a day should seek medical help. Some elderly people may be confused, lethargic, and show general deterioration.

Symptoms of Atypical Pneumonia

General Symptoms for Atypical Pneumonias. Atypical pneumonia is most commonly caused by mycoplasma, Legionnaires' disease, or chlamydia and usually appears in children and young adults.

The disease progresses gradually:

  • General flu-like symptoms often occur first. They may include fatigue, fever, weakness, headache, nasal discharge, sore throat, earache, and stomach and intestinal distress.
  • Vague pain under and around the breastbone may occur, but the severe chest pain associated with typical bacterial pneumonia is uncommon.
  • Patients may have a severe hacking cough, but it usually does not produce sputum.

In-Depth From A.D.A.M. Prognosis

Between 5 and 10 million people get pneumonia in the United States each year, and more than 1 million people are hospitalized due to the condition. As a result, pneumonia is the third most frequent cause of hospitalizations (births are first, and heart disease is second). About 500,000 children are hospitalized for respiratory infections each year, and a third of them have pneumonia.

Although the majority of pneumonias respond well to treatment, the infection kills 40,000 - 70,000 people each year.

Outlook for High-Risk Individuals

Hospitalized Patients. For patients who need hospitalization for pneumonia, the death rate is 10 - 25%. If pneumonia develops in patients already hospitalized for other conditions, death rates range from 50 - 70%, and are higher in women than in men.

Older Adults. Community-acquired pneumonia is responsible for 350,000 - 620,000 hospitalizations in the elderly every year. Older adults have lower survival rates than younger people. Even when older individuals recover from CAP, they have higher-than-normal death rates over the next several years. Elderly people who live in nursing homes or who are already sick are at particular risk.

Very Young Children. Small children who develop pneumonia and survive are at risk for developing lung problems in adulthood, including chronic obstructive pulmonary disease (COPD). Research suggests that men with a history of pneumonia and other respiratory illnesses in childhood are more than twice as likely to die of COPD as those without a history of childhood respiratory disease.

Pregnant Women. Pneumonia poses a special hazard for pregnant women, possibly due to changes in a pregnant woman's immune system. This complication can lead to premature labor and increases the risk of death during pregnancy.

Patients With Impaired Immune Systems. Pneumonia is particularly serious in people with impaired immune systems. This is especially true for AIDS patients, in whom pneumonia causes about half of all deaths.

Patients With Serious Medical Conditions. Pneumonia is also very dangerous in people with diabetes, cirrhosis, sickle cell disease, cancer, and in those whose spleens have been removed.

Risk by Organisms

Specific organisms vary in their effects. Mild pneumonia is usually associated with the atypical organisms mycoplasma and chlamydia. Severe pneumonia is most often associated with a wide range of organisms. Some are very potent (virulent) but extremely curable, while others are difficult to treat:

  • Mycoplasma and chlamydia are the most common causes of mild pneumonias and are most likely to occur in children and young adults. They rarely require hospitalization when they are appropriately treated, although recovery may still be prolonged. Severe and life-threatening cases are more likely to occur in elderly people with other medical conditions.
  • Streptococcus pneumoniae is the most common cause of pneumonia and, in fact, all bacterial upper respiratory infections. It can produce severe pneumonia, with mortality rates of 10%. Nevertheless, pneumococcal pneumonia responds very well to many antibiotics.
  • Staphylococcus aureus is a Gram-positive bacterium that often causes severe pneumonia in hospitalized and high-risk patients and following influenza A and B. People who get this form of pneumonia may develop pockets of infection in their lungs (abscesses) that are difficult to treat and can cause the death of lung tissue (necrosis). Mortality rates are 30 - 40%, in part because the patients who develop this infection are generally very ill or vulnerable.
  • Pseudomonas aeruginosa and Klebsiella pneumoniae are Gram-negative bacteria that pose a risk for abscesses and severe lung tissue damage.
  • Legionella pneumophila is very virulent and can cause widespread damage. Treatments have improved dramatically since it was first identified. However, a 2002 study suggested that many patients experience long-term problems, including coughing, shortness of breath, fatigue, and neurological and muscular complications.
  • Viral pneumonia is usually very mild, but there are exceptions. Respiratory syncytial virus (RSV) pneumonia rarely poses a danger for healthy young adults, but it can be life-threatening in infants and serious in the elderly.

Complications of Pneumonia

Abscess. An abscess in the lung is a thick-walled, pus-filled cavity that forms when infection has destroyed lung tissue. It typically occurs as a result of aspiration pneumonia, when a mixture of organisms is carried into the lung. Untreated abscesses can cause hemorrhage (bleeding) in the lung, but targeted antibiotic therapy significantly reduces their danger. Abscesses are more common with Staphylococcus aureus, Pseudomonas aeruginosa, or Klebsiella pneumoniae, and are uncommon with Streptococcus pneumoniae.

Respiratory Failure. Respiratory failure is one of the top causes of death in patients with pneumococcal pneumonia. Acute respiratory distress syndrome (ARDS) is the specific condition that occurs when the lungs are unable to function and oxygen is so severely reduced that the patient's life is at risk. Failure can occur if pneumonia leads to mechanical changes in the lungs (ventilatory failure) or oxygen loss in the arteries (hypoxemic respiratory failure).

Bacteremia. Bacteremia -- bacteria in the blood -- is the most common complication of pneumococcus infection, although it rarely spreads to other sites. Bacteremia is a frequent complication of infection from Gram-negative organisms, including Haemophilus influenzae.

Pleural Effusions and Empyema. The pleura are two thin membranes that line the chest and lungs:

  • The visceral pleura cover the lungs.
  • The parietal pleura cover the chest wall.

In some cases of pneumonia the pleura become inflamed, which can result in breathlessness and acute chest pain when breathing.

In about 20% of pneumonia cases fluid builds up between the pleural membranes, a condition known as pleural effusion. Ordinarily, the narrow zone between the two membranes contains only a tiny amount of fluid, which lubricates the lungs.

In most cases, particularly in Streptococcus pneumoniae, the fluid remains sterile (no bacteria are present), but occasionally it can become infected and even filled with pus, a condition called empyema. Empyema is more likely to occur with specific organisms such as Staphylococcus aureus or Klebsiella pneumoniae infections. The condition can cause permanent scarring.

Collapsed Lung. In some cases, air may fill up the area between the pleural membranes, causing the lungs to collapse. This is called pneumothorax. It may be a complication of pneumonia (particularly Streptococcus pneumoniae ) or of the invasive procedures used to treat pleural effusion.

Pneumothorax occurs when air leaks from inside the lung to the space between the lung and the chest wall. The lung then collapses. The dark side of the chest (right side of the picture) fills with air from outside of the lung tissue.

Other Complications of Pneumonia. In rare cases, infection may spread from the lungs to the heart and possibly throughout the body. This can cause abscesses in the brain and other organs. Coughing up blood (hemoptysis) is another potentially serious complication of pneumonia, particularly in patients with lung problems such as cystic fibrosis. At least one study has also linked bacterial pneumonia with an increased risk of acute heart problems, such as heart attack or arrhythmia.

Kidney complications and electrolyte imbalances are common in patients admitted to the hospital with pneumonia. If not treated, these problems cause more severe illness and increase the risk of death. Treatment with intravenous saline can usually resolve the problem.

Long-Term Effects of Atypical Pneumonias

Pneumonias cased by the atypical organisms mycoplasma and chlamydia are usually mild. Some research suggests, however, that chlamydia may have powerful inflammatory effects in the blood vessels. This effect may have certain adverse long-term consequences, even in healthy younger individuals.

Asthma. Chlamydia pneumoniae, Mycoplasma pneumoniae, and RSV are becoming suspects in many cases of severe adult asthma. One small Australian study found evidence of previous chlamydia infection in 64% of the patients with asthma who were tested.

In-Depth From A.D.A.M. Risk Factors

Risk factors for pneumonia often depend on the specific type of disease.

Risk Factors for Institutional- and Hospital-Acquired (Nosocomial) Pneumonia

Pneumonia that is contracted in the hospital is called hospital-acquired or nosocomial pneumonia. It affects an estimated 5 - 10 of every 1,000 hospitalized patients every year. More than half of these cases may be due to strains of bacteria that have developed resistance to antibiotics. In fact, methicillin-resistant Staphylococcus aureus and multidrug-resistant Pseudomonas aeruginosa are leading causes of death from hospital-acquired pneumonia. Those at highest risk:

  • The elderly and very young.
  • People with chronic or severe medical conditions, such as lung problems, heart disease, neurologic disorders, and cancer.
  • People who have had surgery, particularly people over age 80. Among the surgical procedures that pose a particular risk are removal of the spleen (splenectomy), abdominal aortic aneurysm repair, or operations that impair coughing.
  • People who have been in the intensive care unit (ICU). This is particularly true for newborns or patients on breathing machines (mechanical ventilators). In one study, 10% of ICU patients on a breathing machine developed pneumonia. Such patients who lie flat on their backs are at particular risk for aspiration pneumonia. Raising the patient up may reduce this risk.
  • People who have received sedation. Hospital patients who receive sedatives also have a higher risk of developing nosocomial pneumonia.

Hospitalized patients are particularly vulnerable to Gram-negative bacteria and staphylococci, which can be especially dangerous in people who are already ill.

Risk Factors for Community-Acquired Pneumonia (CAP)

CAP is the most common type of pneumonia. It develops outside of the hospital. Each year 2 - 4 million people in the US develop CAP, and 600,000 are hospitalized. The elderly, infants, and young children are at greatest risk for the disease.

Chronic Lung Disease. Chronic obstructive lung disease (COPD), which includes chronic bronchitis and emphysema, affects 15 million people in the U.S. This condition is a major risk factor for pneumonia. In patients with COPD, vaccination with the pneumococcal vaccine can substantially reduce the risk of developing pneumonia or decrease its severity.

Bronchitis is the inflammation of the bronchi, the main air passages to the lungs. It generally follows a viral respiratory infection. Symptoms include coughing, shortness of breath, wheezing, and fatigue.

People With Compromised Immune Systems. People with impaired immune systems are extremely susceptible to pneumonia. It is a common problem in people with HIV and AIDS. A wide variety of organisms, including Myobacterium species, Histoplasma capsulatum, Coccidioides immitis, Aspergillus species, cytomegalovirus, and Toxoplasma gondii, can cause pneumonia.

In addition to AIDS, other conditions that compromise the immune system include:

  • Adult and pediatric cancers, especially leukemia and Hodgkin's lymphoma
  • Chemotherapy
  • Organ transplantation

Patients who are on corticosteroids or other medications that suppress the immune system are also prone to infection.

Also, drugs that treat gastroesophageal reflux (GERD) may slightly increase one's risk for community-acquired pneumonia. Patients at high risk for pneumonia should take gastric acid-suppressing drugs only when necessary and at the lowest possible dose. This association is strongest with protein pump inhibitors (PPIs) such as Prilosec and Nexium. Reducing levels of germ-killing stomach acid may allow germs to spread in the upper gastrointestinal tract and move into the respiratory tract. The risk posed by these medications is highest in:

  • Children
    • Patients with asthma, COPD, and compromised immune systems
  • The elderly

Researchers have found that the risk is strongest when people have recently begun treatment with PPIs, and lessens over time.

Swallowing disorders, including dysphagia. Difficulty swallowing has a variety of causes, including:

  • Abnormalities of the muscles of the esophagus
  • Illnesses such as Parkinson's disease
  • Neurologic disorders involving the esophagus
  • Stroke
  • Surgical or radiation treatment for cancers of the mouth, throat, or esophagus
  • Traumatic brain injuries

All of these may increase the risk of aspiration pneumonia.

Dementia. The impaired vigilance while swallowing contributes to an increased risk of aspiration pneumonia.

Gastroesophageal Reflux Disease. Gastroesophageal reflux disease (GERD) is a condition in which acids from the stomach move up into the esophagus. This is called reflux. Current studies indicate an association between GERD and various problems that occur in the sinuses, ears, nasal passages, and airways of the lung. People with GERD appear to have an above-average risk for:

  • Chronic bronchitis
  • Chronic sinusitis
  • Emphysema
  • Lung scarring (pulmonary fibrosis)
  • Recurrent pneumonia

If a person inhales fluid (aspirates) from the esophagus into the lungs, it may trigger inflammation in these upper passages.

Factors Associated with a Higher Risk in Healthy Adults

Dormitory or Barrack Conditions. Recruits on military bases and college students living in dormitories are at higher-than-average risk for Mycoplasma pneumonia. These groups are at lower risk, however, for more serious types of pneumonia.

Smoke and Environmental Pollutants. The risk for pneumonia in people who smoke more than a pack a day is three times that of nonsmokers. Those who are chronically exposed to secondhand cigarette smoke, which can injure airways and damage the cilia, are also at risk. Quitting smoking reduces the risk of dying from pneumonia to normal, but the full benefit takes 10 years to be realized. Toxic fumes, industrial smoke, and other air pollutants may also damage cilia function, which is a defense against bacteria in the lungs.

Drug and Alcohol Abuse. Alcohol or drug abuse is strongly associated with pneumonia. These substances act as sedatives and can diminish the reflexes that trigger coughing and sneezing. Alcohol also interferes with the actions of macrophages, the white blood cells that destroy bacteria and other microbes. Intravenous drug abusers are at risk for pneumonia from infections that start at the injection site and spread through the bloodstream to the lungs.

Specific Risk Factors for Recurrent Pneumonia in Children

Certain children have a higher-than-normal risk for pneumonia and recurrence. Conditions that predispose infants and small children to pneumonia include:

  • Abnormalities in muscle coordination of the mouth and throat
  • Asthma
  • Certain genetic disorders such as sickle-cell disease, cystic fibrosis, and Kartagener's syndrome, which result in poorly functioning cilia, the hair-like cells lining the airways
  • Gastroesophageal reflux disorder (GERD)
  • Impaired immune system
  • Inborn lung or heart defects
  • Infection with the respiratory syncytial virus (RSV)
  • Leukemia

In-Depth From A.D.A.M. Diagnosis

Diagnostic Difficulties in Community-Acquired Pneumonia (CAP). It is important to determine whether the cause of CAP is a bacterium, atypical bacterium, or virus, because they require different treatments. In children, for example, S. pneumonia is the most common cause of pneumonia, but respiratory syncytial virus may also cause the disease. Although symptoms may differ, they often overlap, which can make it difficult to identify the organism by symptoms alone. The cause of CAP is found in only about half of cases.

Nevertheless, in many cases of mild-to-moderate CAP, the physician is able to diagnose and treat pneumonia based solely on a history and physical examination.

Diagnostic Difficulties with Hospital-Acquired (Nosocomial) Pneumonia. Diagnosing pneumonia is particularly difficult in hospitalized patients for a number of reasons:

  • Many hospitalized patients have similar symptoms, including fever or signs of lung infiltration on x-rays.
  • In hospitalized patients, sputum or blood tests often indicate the presence of bacteria or other organisms, but such agents do not necessarily indicate pneumonia.

Doctors making a diagnosis of pneumonia should rule out other conditions using:

  • Chest x-ray
  • Lung fluid sample
  • Two sets of blood cultures
  • Urine analysis for legionella

Medical and Personal History

The patient's history is an important part of making a pneumonia diagnosis. Patients should be sure to report any of the following:

  • Alcohol or drug abuse
  • Exposure to people with pneumonia or other respiratory illnesses (such as tuberculosis)
  • History of smoking
  • Occupational risks
  • Recent or chronic respiratory infection
  • Recent travel

Physical Examination

Use of the Stethoscope. The most important diagnostic tool for pneumonia is the stethoscope. Sounds in the chest that may indicate pneumonia include:

  • Rales, a bubbling or crackling sound. Rales on one side of the chest or that are heard while the patient is lying down strongly suggest pneumonia.
  • Rhonchi, abnormal rumblings indicating that there is sputum in the large airways.
  • A dull thud. The physician will use a test called percussion, in which the chest is tapped lightly. A dull thud, instead of a hollow drum-like sound, indicates certain conditions that suggest pneumonia. These conditions include consolidation (in which the lung becomes firm and inelastic) and pleural effusion (fluid build-up in the space between the lungs and the lining around it).

Laboratory Tests for Diagnosing Infection and Identifying Bacteria

Although current antibiotics can destroy a wide spectrum of organisms, it is best to use an antibiotic that targets the specific one making a person sick. Unfortunately, people carry many bacteria, and sputum and blood tests are not always effective in distinguishing between harmless and harmful kinds.

In severe cases, a doctor needs to use invasive diagnostic measures to identify the cause of the infection. Standard lab tests used to help diagnose pneumonia include:

Sputum Tests. The color of the mucus (sputum) sample coughed up from the lungs can reveal the severity of the disease. Only a sputum sample will reveal the organism causing the infection.

The patient coughs as deeply as possible to bring up mucus from the lungs, since a shallow cough produces a sample that usually only contains normal mouth bacteria. Some people may need to inhale a saline spray to produce an adequate sample. In some cases, a tube will be inserted through the nose into the lower respiratory tract to trigger a deeper cough.

The physician will check the sputum for:

  • Blood, which means an infection is present.
  • Color and consistency: If it is yellow, green, or brown, an infection is likely.

The sputum sample is sent to the laboratory, where it is analyzed for the presence of bacteria and to determine whether the bacteria are Gram-negative or Gram-positive.

Blood Tests. The following blood tests may be performed:

  • White blood cell count (WBC). High levels indicate infection.
  • Blood cultures. Cultures are done to determine the specific organism causing the pneumonia, but they usually cannot distinguish between harmless and dangerous organisms. They are accurate in only 10 - 30% of cases. Their use is generally limited to severe cases.
  • Detection of antibodies to S. pneumoniae. Antibodies are immune factors that target specific foreign invaders. One type of immunohistochemical test for S. pneumoniae is showing tremendous promise. The presence of antibodies that are responding to mycoplasma or chlamydia infection are not present early enough in the course of pneumonia to allow for prompt diagnosis and treatment.
  • Polymerase Chain Reaction (PCR). In some difficult cases, PCR may be performed. The test makes multiple copies of the genetic material (RNA) of a virus or bacteria to make it detectable. PCR is useful for identifying certain atypical bacteria strains, including mycoplasma and Chlamydia pneumoniae, and possibly, Haemophilus influenzae type b, but it is expensive. One study found that using a real-time PCR test may help quickly diagnose Pneumocystitis pneumonia in HIV-positive patients.

Urine Tests. Urine antigen tests for Legionella pneumophila (Legionnaires' disease) and Streptococcus pneumoniae may be performed in patients with severe CAP. The S. pneumoniae test takes only 15 minutes and may identify up to 77% of pneumonia cases and rule out S. pneumoniae infection in 98% of patients. It may not be useful in children.

Invasive Tests. In critically-ill patients with ventilator-associated pneumonia, physicians have tried sampling fluid taken from the lungs or trachea. These techniques enabled the physicians to identify the pneumonia-causing bacteria and start the appropriate antibiotics. However, this made no difference in the length of stay in the ICU or hospital, and there was no significant difference in outcome.

Chest X-Rays and Other Imaging Techniques

X-Rays. A chest x-ray is nearly always taken to confirm a diagnosis of pneumonia.

X-rays are a form of electromagnetic radiation (like light). They are of higher energy, however, and can penetrate the body to form an image on film. Structures that are dense (such as bone) will appear white, air will be black, and other structures will be shades of gray depending on density. X-rays can provide information about obstructions, tumors, and other diseases, especially when coupled with the use of barium and air contrast within the bowel.

A chest x-ray may reveal the following:

  • Complications of pneumonia, including pleural effusions and abscesses
  • White areas in the lung called infiltrates, which indicate infection

Other Imaging Tests. Computed tomography (CT) scans or magnetic resonance imaging (MRI) scans may be useful in some circumstances, especially when:

  • A lung tumor is suspected
  • Complications occur
  • Patients do not respond to antibiotics
  • Patients have other serious health problems
  • Pulmonary embolism is suspected
  • X-ray results are unclear

CT and MRI can help detect the presence of tissue damage, abscesses, and enlarged lymph nodes. They can also detect some tumors that block bronchial tubes. No imaging technique can determine the actual organism causing the infection. However, features on the CT scan of patients with certain forms of pneumonia -- for example, that caused by Legionella pneumophila -- are usually different from features produced by other bacteria in the lungs.

Invasive Diagnostic Procedures

Invasive diagnostic procedures may be required when:

  • AIDS or other immune problems are present
  • Patients have life-threatening complications
  • Standard treatments have failed for no known reason

Invasive procedures include:

Thoracentesis. If a doctor detects pleural effusion during the physical exam or on an imaging study, and suspects that pus (empyema) is present, a thoracentesis is performed.

  • Fluid in the pleura is withdrawn using a long thin needle inserted between the ribs.
  • The fluid is then sent to the lab for multiple tests.

Complications of this procedure are rare, but can include collapsed lung, bleeding, and introduction of infection.

Bronchoscopy. Bronchoscopy is an invasive test to examine respiratory secretions. It is not usually needed in patients with community-acquired pneumonia, but it may be appropriate for patients with severely compromised immune systems who need immediate diagnosis, or in patients whose condition has worsened during treatment.

A bronchoscopy is done in the following way:

  • The patient is given a local anesthetic, supplementary oxygen, and sedatives.
  • The physician inserts a fiber optic tube into the lower respiratory tract through the nose or mouth.
  • The tube acts like a telescope into the body, allowing the physician to view the windpipe and major airways and look for pus, abnormal mucus, or other problems.
  • The doctor removes specimens for analysis and can also treat the patient by removing any foreign bodies or infected tissue encountered during the process.

Bronchoalveolar lavage (BAL) may be done at the same time as bronchoscopy. This involves injecting high amounts of saline through the bronchoscope into the lung and then immediately sucking the fluid out. The fluid is then analyzed in the laboratory. Studies find BAL to be an effective method for detecting specific infection-causing organisms.

The procedure is usually very safe, but complications can occur. They include:

  • Allergic reactions to the sedatives or anesthetics
  • Asthma attacks in susceptible patients
  • Bleeding
  • Fever

Lung Biopsy. In very severe cases of pneumonia or when the diagnosis is unclear, particularly in patients with damaged immune systems, a lung biopsy may be required. A lung biopsy involves taking some tissue from the lungs and examining it under a microscope.

Lung Tap. This procedure typically uses a needle inserted between the ribs to draw fluid out of the lung for analysis. It is known by a number of names, including:

  • Lung aspiration
  • Lung puncture
  • Thoracic puncture
  • Transthoracic needle aspiration
  • Percutaneous needle aspiration
  • Needle aspiration

It is a very old procedure that is not done often any more, since it is invasive and poses a slight risk for collapsed lung. Some experts argue, however, that a lung tap is more accurate than other methods for identifying bacteria, and the risk it poses is slight. Given the increase in resistant bacteria, they believe its use should be reconsidered in young people.

Ruling Out Other Disorders that Cause Coughing or Affect the Lung

Common Causes of Persistent Coughing. Over 30 million people seek medical help each year for persistent coughing, which is nearly always temporary and harmless when other symptoms, such as fever, are not present. The four most common causes of persistent coughing are:

  • Asthma
  • Chronic bronchitis
  • Gastroesophageal reflux disease (GERD)
  • Postnasal drip

Other obvious common causes of chronic cough include heavy smoking or the use of heart drugs known as ACE inhibitors.

Acute Bronchitis. Acute bronchitis is an infection in the passages that carry air from the throat to the lung. The infection causes a cough that produces phlegm. Acute bronchitis is almost always caused by a virus and usually clears up on its own within a few days. In some cases, acute bronchitis caused by a cold can last for several weeks.

Chronic Bronchitis. Chronic bronchitis causes shortness of breath and is often accompanied by infection, mucus production, and coughing, but it is a long-term and irreversible condition. The same microbes that cause pneumonia can cause chronic bronchitis, and symptoms of the two disorders are often similar. They include:

  • Coughing
  • Fatigue
  • Fever
  • Sputum production

There are significant differences between chronic bronchitis and pneumonia:

  • Patients with bronchitis are less likely to have wheezing, shortness of breath, chills, very high fevers, and other signs of severe illness.
  • Those with pneumonia usually cough up heavy sputum, which is also more likely to contain blood.
  • X-rays of patients with bronchitis do not show fluid or consolidation in the lung.

Asthma. In asthma, the cough is accompanied by wheezing and occurs mostly at night or during activity. Fever is rarely present (unless the patient also has an infection). Asthma symptoms from occupational causes can lead to persistent coughing, which is usually worse during the work week. Tests -- the methacholine inhalation challenge and pulmonary function studies -- may be effective in diagnosing asthma.

Anthrax. Because of current terrorist concerns, it is important to differentiate between anthrax and community-acquired pneumonia. According to one study, people with inhalation anthrax are more likely to have rapid heart rate and less likely to have headache, nasal symptoms, and muscle aches than those with pneumonia. Blood tests with anthrax also show high hematocrit and low albumin and sodium levels. Certain chest x-ray findings also raise the likelihood of anthrax.

Other Disorders that Affect the Lung. Many conditions mimic pneumonia, particularly in hospitalized patients. They include:

  • Acute respiratory distress syndrome (ARDS)
  • Atelectasis, a collapse of lung tissue
  • Bronchial asthma
  • Bronchiectasis, an irreversible widening of the airways usually associated with birth defects, chronic sinus or bronchial infection, or blockage
  • Heart failure (if it affects the left side of the heart, fluid build-up can occur in the lungs and cause persistent cough, shortness of breath, and wheezing)
  • Interstitial pulmonary fibrosis, a non-infectious inflammation of the lung marked by progressive damage and scarring
  • Lung cancer
  • Severe allergic reactions, such as reactions to drugs
  • Tuberculosis

Ruling Out Causes in Children. Important causes of coughing in children at different ages include:

  • Asthma
  • Physical abnormalities in infants under 18 months
  • Psychological causes in older children and adolescents
  • Sinusitis in children 18 months - 6 years

In-Depth From A.D.A.M. Treatment

The approach to treating patients with pneumonia generally involves:

  • Deciding who can be treated at home and who needs to be in the hospital
  • Deciding whether a patient needs antibiotics, and which antibiotics are appropriate
  • Providing appropriate supportive care
  • Deciding what follow-up and preventive care are needed

Determining the Need for Hospitalization

Up to 10% of all adult hospitalizations in the U.S. are due to community-acquired pneumonia. Studies indicate that many patients do not need to be hospitalized for pneumonia, and can be safely treated at home. Likewise, many patients who are admitted to the hospital could be released sooner. A number of strategies are being devised to determine when and which patients can be safely discharged. Studies have shown that low-risk patients with mild-to-moderate pneumonia do just as well when treated as outpatients and return to work and normal activities faster than those treated in the hospital.

A variety of guidelines and tools have been developed to help determine who can safely be treated at home and who cannot. One commonly used tool is called the Pneumonia Severity Index. All of these assessment tools are looking for risk factors, and the more of these risk factors that are present, the less likely that the patient can be safely treated at home. Several of these risk factors determine a specific score. All of them must be used along with the doctor's clinical judgment.

Some of the important factors used to make a decision include:


  • Patients who have been living in a nursing home or other residential facility are of greater concern.
  • Elderly patients and infants, particularly infants who are less than 1 month old, are more likely to be admitted.

Other Medical Illnesses. Patients may be considered at greater risk if they have:

  • Cancer
  • Heart failure
  • History of stroke
  • Kidney failure
  • Liver disease

Findings on a Physical Exam. Concerning findings include:

  • Altered mental status (confused, less responsive)
  • Appearance of being dehydrated, especially if the person is unable to drink fluids
  • Fast breathing (more than 30 breaths per minute)
  • Heart rate greater than 120 beats per minute
  • Systolic blood pressure less than 90 mm Hg
  • Temperature greater than 104° F

Laboratory and X-ray Findings. Laboratory findings that are of concern include:

  • Elevated blood sugar
  • Fluid in the sac around the lung (on chest x-ray)
  • Low oxygen in the blood
  • Low sodium levels
  • Poor kidney function
  • Significant anemia (hematocrit less than 30%)

Patients with very few of these risks often can be discharged with outpatient care only. This determination can often be done with a simple physical examination and history. Sometimes a patient only needs to be hospitalized for 24 hours for observation.

Patients with higher scores on these assessment tests often have many risk factors and usually are hospitalized.

When possible, treatment of community-acquired pneumonia should be started within 4 hours of admission to the emergency room or hospital to reduce the chances of mortality and decrease the amount of time a patient needs to spend in the hospital.

Home care may be possible, even in severe cases, when there is good support and available home nursing services. Often, caregivers can even be trained to administer intravenous antibiotics and chest therapy to patients at home.

Home Treatment

The following tips are suggested:

  • Drink plenty of liquids.
  • Do not suppress a cough. Coughing is an important reflex for clearing the lungs. Some doctors advise taking expectorants, such as guaifenesin (Breonesin, Glycotuss, Glytuss, Hytuss, Naldecon Senior EX, Robitussin) to loosen mucus. However, there is no proof that any of these products make much difference in outcome.
  • Mild pain can be treated with aspirin (in adults only), acetaminophen (Tylenol), or ibuprofen (Advil, Motrin).
  • For severe pain, codeine or another stronger pain reliever may be prescribed. It should be noted, however, that codeine and other narcotics suppress coughing, so they should be used with care in pneumonia. Such pain relievers often require monitoring.
  • A laboratory study reported that aromatic oils containing oregano, thyme, and rosewood destroyed S. pneumoniae. It is not known whether they have any effect on pneumonia in people.
  • Practice chest therapy.

Hospitalization Guidelines

Treatment. If the pneumonia is severe enough for hospitalization, the standard treatment is intravenous antibiotics for 5 - 8 days. In cases of uncomplicated pneumonia, many patients may need only 2 or 3 days of intravenous antibiotics followed by oral therapy. Antibiotics taken by mouth are prescribed when the patient has improved substantially or leaves the hospital.

ITSA/ATS guidelines recommend that patients admitted to the hospital (but not the ICU) be treated with fluoroquinolones or a beta-lactam plus a macrolide (preferably cefotaxime or ceftriaxone and ampicillin).

Duration of Stay. Patients should remain in the hospital until all their vital signs are stable. Most patients become stabilized in 3 days. Many experts use seven variables to measure stability and to determine whether the patient can go home:

  • Temperature. (Some experts believe that patients can go home when their temperature drops to 101° F. Stricter criteria require that it be at or close to 98.6° F.)
  • Respiration rate. (Goal is a normal breathing rate, although expert opinion differs on the degree of normality required to be discharged.)
  • Heart rate. (Goal is 100 beats per minute or less.)
  • Blood pressure. (Goal is systolic blood pressure of 90 mm Hg or greater.)
  • Oxygenation. (Goal is determined by the physician.)
  • The ability to eat. (Goal is regular appetite.)
  • Mental function. (Goal is normal.)

Patients or their families should discuss these criteria with their doctor. In a 2002 study, 42% of patients who had two or more signs of instability when they left the hospital were either readmitted or died within 30 days, compared with 10.5% of completely stabilized patients.

Chest Therapy

Chest therapy using incentive spirometry, rhythmic inhalation and coughing, and chest tapping are all important techniques to loosen the mucus and move it out of the lungs. It should be used both in the hospital and during recovery at home.

Incentive Spirometry. The patient uses an incentive spirometer at regular intervals to improve breathing and loosen sputum. The spirometer is a hand-held clear plastic device that includes a breathing tube and a container with a movable gauge. The patient exhales and then inhales forcefully through the tube, using the pressure of the inhalation to raise the gauge to the highest level possible.

Rhythmic Breathing and Coughing. During recovery, the patient performs rhythmic breathing and coughing every 4 hours:

  • Before starting the breathing exercise, the patient should tap lightly on the chest to loosen mucus within the lung. If available, a caregiver should also tap on the patient's back.
  • The patient inhales rhythmically and deeply 3 or 4 times.
  • The patient then coughs as deeply as possible with the goal of producing sputum.

In-Depth From A.D.A.M. Antibiotic and Antiviral Drug Classes


Beta-lactam antibiotics share common chemical features. They include penicillins, cephalosporins, and some newer similar medications. They interfere with bacterial cell walls.

Penicillins. Penicillin was the first antibiotic. There are many forms to this still-important drug:

  • Natural penicillins include penicillin G (for intravenous use) and V (for oral use).
  • Penicillin derivatives called aminopenicillins, particularly amoxicillin (Amoxil, Polymox, Trimox, Wymox, or any generic formulation), are now the most common penicillins used. Amoxicillin is inexpensive and, at one time, was highly effective against S. pneumoniae. Unfortunately, bacterial resistance to amoxicillin has increased significantly, both among S. pneumoniae and H. influenzae. Ampicillin is similar and is an alternative to amoxicillin, but requires more doses and has more severe gastrointestinal side effects.
  • Amoxicillin-clavulanate (Augmentin) is an augmented penicillin that works against a wide spectrum of bacteria. An extended-release form has been approved for treating adults with community-acquired pneumonia caused by bacterial strains that have become resistant to penicillin.
  • Antistaphylococcal penicillins were developed to treat Staphylococcus aureus. The standard drug was methicillin, but it is no longer used routinely due to very high rates of resistance in hospital-acquired pneumonias. Resistance in community-acquired Staphylococcus aureus is also increasing. Alternatives include vancomycin and linezolid. Cefazolin and clindamycin are other options for this type of bacteria.
  • Certain penicillins used against Pseudomonas aeruginosa include ticarcillin and piperacillin. Piperacillin is more effective than ticarcillin.

Many people have a history of an allergic reaction to penicillin, but research suggests that the allergy may not recur in a significant number of adults. Skin tests are available to help determine if those with a history of penicillin allergies could use these important antibiotics.

Cephalosporins. Most of these agents are not very effective against bacteria that have developed resistance to penicillin. They are classed according to their generation:

  • First generation includes cephalexin (Keflex), cefadroxil (Duricef, Ultracef), and cephradine (Velosef).
  • Second generation includes cefaclor (Ceclor), cefuroxime (Ceftin), cefprozil (Cefzil), and loracarbef (Lorabid),
  • Third generation includes cefpodoxime (Vantin), cefdinir (Omnicef) cefditoren (Sprectracef), cefixime (Suprax), and ceftibuten (Cedex). Ceftriaxone (Rocephin) is an injected cephalosporin. These are effective against a wide range of Gram-negative bacteria. Cefditoren has also been shown to be 85% effective against Haemophilus influenzae and 90% effective against penicillin-resistant strains of S. pneumoniae.

Other Beta-Lactam Agents. Carbapenems include meropenem (Merrem), biapenem, faropenem, ertapenem (Invanz) and combinations (imipenem/cilastatin [Primaxin]). These agents cover a wide spectrum of bacteria. They are now used for serious hospital-acquired infections and for bacteria that have become resistant to other beta-lactams. Imipenem has serious side effects when used alone, so it is given in combination with cilastatin to offset these adverse effects. The newer agents are less toxic, although they may not be as potent.

Sanfetrinem, a novel beta-lactam antibiotic known as a trinem is proving to be effective against S. pneumoniae, H. influenzae, and M. catarrhalis.

Ceftobiprole is an investigational beta-lactam in phase III clinical trials for methicillin-resistant Staphylococcus aureus (MRSA), penicillin-resistant streptococci, and other Gram-negative pathogens. Other anti-MRSA beta-lactams in clinical development include:

  • CS-023/RO-4908463, a carbapenem
  • Ceftaroline, a cephalosporin (PPI-0903)


Fluoroquinolones (quinolones) interfere with bacteria''s genetic material to prevent them from reproducing.

  • Ciprofloxacin (Cipro), a second-generation quinolone, remains the most potent quinolone against Pseudomonas aeruginosa. It is not very effective for Gram-positive bacteria such as Streptococcus pneumoniae.
  • "Respiratory" quinolones are currently the most effective drugs available for a wide range of bacteria. Such drugs include levofloxacin (Levaquin), sparfloxacin (Zagam), and gemifloxacin (Factive). Some of the newer fluoroquinolones only need to be taken once a day.
  • The fourth-generation quinolones moxifloxacin (Avelox) and clinafloxacin, which is still under development, are proving to be effective against anaerobic bacteria.

S. pneumoniae -- strains resistant to the "respiratory" quinolones are uncommon in the U.S., but resistance is dramatically increasing.

Many quinolones cause side effects, including:

  • Neurologic, psychiatric, and heart problems
  • Sensitivity to light

Pregnant women should not take these medications. The drugs also enhance the potency of oral anti-clotting agents.

Macrolides, Azalides, and Ketolides

Macrolides and azalides also affect the genetics of bacteria. These medications include:

  • Azithromycin (Zithromax, Zmax)
    • Clarithromycin (Biaxin)
  • Erythromycin
  • Roxithromycin (Rulid)

These antibiotics are effective against atypical bacteria such as mycoplasma and chlamydia. Macrolides are also used in some cases for S. pneumoniae and M. catarrhalis, but there is increasing bacterial resistance to these agents. All but erythromycin are effective against H. influenzae. Macrolide-resistance rates doubled between 1995 and 1999 as more and more children were being treated with these antibiotics. Some research suggests these agents may reduce the risk of a first heart attack in some patients by reducing inflammation in the blood vessels.

Extended-release (ER) azithromycin (Zmax) is the first anti-pneumonia antibiotic that can be given in a single dose. It is effective against Gram-positive, Gram-negative, and atypical pathogens. Studies have shown the results to be equal to those ahchieved with 7 days of levofloxacin or clarithromycin ER in patients with CAP. A single-dose antibiotic decreases the likelihood that a patient will discontinue taking the antibiotic early, which rapidly contributes to the development of drug-resistant bacteria.

Ketolides. Ketolides are a new class of antibiotic drugs. They are derived from erythromycin and were developed to combat organisms that have become resistant to macrolides. Telithromycin (Ketek), the first antibiotic in the ketolide class, was approved by the FDA in 2004 for the treatment of community-acquired pneumonia (CAP).

In February 2007, the FDA withdrew approval of Ketek for the treatment of acute bacterial sinusitis. The agency decided that the serious risks of telithromycin outweigh its benefits for sinusitis treatment. The decision followed several 2006 reports of patient deaths due to severe liver damage.

Telithromycin is still approved for the treatment of CAP, but the drug carries a black box warning noting the potentially serious side effects, including:

  • Liver failure
  • Loss of consciousness
    • Neuromuscular problems
  • Vision problems

Because of these side effects, telithromycin is only approved for patients with mild-to-moderate community-acquired pneumonia caused by penicillin- or macrolide-resistant S. pneumoniae. Other treatments are as effective, and are safer.


Tetracyclines inhibit bacterial growth. They include doxycycline, tetracycline, and minocycline. They can be effective against S. pneumoniae and M. catarrhalis, but bacteria that are resistant to penicillin are also often resistant to doxycycline. The side effects of tetracyclines include:

  • Burning in the throat
  • Skin reactions to sunlight
  • Tooth discoloration


Aminoglycosides (gentamicin, kanamycin, tobramycin, amikacin) are given by injection for very serious bacterial infections. They can be given only in combination with other antibiotics. Some are available in inhaled forms or by applying a solution directly to mucus membranes, skin, or body cavities. They can have very serious side effects, including:

  • Balance problems
  • Hearing damage
  • Kidney damage


Lincosamides prevent bacteria from reproducing. The most common lincosamide is clindamycin (Cleocin). This antibiotic is useful against S. pneumoniae and S. aureus, but not against H. influenzae.


Glycopeptides (vancomycin, teicoplanin) are used for Staphylococcus aureus infections that have become resistant to standard antibiotics. The drug can be taken by mouth or given intravenously. The latest generation of glycopeptides, a derivative of vancomycin, is called telavancin. Currently in phase III studies of hospital-acquired pneumonia, it looks positive for the treatment of Gram-positive pneumonia.


Trimethoprim-sulfamethoxazole (Bactrim, Cotrim, Septra) is less expensive than amoxicillin. It is particularly useful for adults with mild bacterial upper respiratory infections who are allergic to penicillin. The drug is no longer effective against certain streptococcal strains. It should not be used in patients whose infections occur after dental work, or in people who are allergic to sulfa drugs. Allergic reactions can be very serious.


Linezolid (Zyvox) is the first antibacterial drug in a new class of synthetic antibiotics called oxazolidinones. It has been shown to work against certain aerobic Gram-positive bacteria.

Other Agents

Inhaled polymyxin, a drug used in cystic fibrosis patients, is showing efficacy against pneumonia caused by multidrug-resistant Gram-negative bacteria, including pseudomonas and klebsiella.

In-Depth From A.D.A.M. Medications

Dozens of antibiotics are available for treating pneumonia, but selecting the best drug is sometimes difficult. Patients with pneumonia need an antibiotic that is effective against the organism causing the disease. When the organism is unknown, "empiric therapy" is given, meaning the doctor chooses which antibiotic is likely to work based on factors such as the patient's age, health, and severity of the illness.

In determining the appropriate antibiotic, the physician must first answer a number of questions:

  • How severe is the pneumonia? Mild-to-moderate cases can be treated at home with oral antibiotics, while severe pneumonia usually needs intravenous antibiotics administered in the hospital.
  • If the organism causing the pneumonia is not known, was the disorder community- or hospital-acquired? Different organisms are usually involved in each setting, and the physician can use this information to guess the most likely organism causing the pneumonia.
  • If the organism is known, is it typical or atypical? Community-acquired pneumonias, for example, are usually caused by the typical bacteria Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis, which have traditionally been treated with penicillin or other standard antibiotics. These antibiotics do not affect atypical organisms, such as legionella, mycoplasma, or chlamydia. These organisms are generally treated with a macrolide or possibly a newer quinolone.
  • Does the patient have an impaired immune system? Antibiotics used to treat such patients may differ from those used in patients with healthy immune systems.

Once an antibiotic has been chosen, there are still difficulties:

  • Individuals respond differently to the same antibiotic, depending on their age, health, size, and other factors.
  • Patients can be allergic to certain antibiotics, thus requiring alternatives.
  • Patients may harbor strains of bacteria that are resistant to certain antibiotics.

Antibiotic Treatments for Community-Acquired Pneumonia

Joint guidelines issued in 2007 by the Infectious Disease Society of America and the American Thoracic Society (ITSA/ATS) recommend that mild CAP in otherwise healthy patients be treated with oral macrolide antibiotics (azithromycin, clarithromycin, or erythromycin).

Many patients with heart disease, kidney disease, diabetes, or other comorbid conditions may still be treated as outpatients. However, they should be given a fluoroquinolone (moxifloxacin, gemifloxacin, or levofloxacin) or a beta-lactam (preferably high-dose amoxicillin or amoxicillin-clavulanate), plus a macrolide, unless they live in an area with high S. pneumoniae resistance to macrolides.

Research has not pinpointed an exact duration of antibiotic therapy. Current recommendations call for 7 - 10 days of treatment for S. pneumoniae and 10 - 14 days for Mycoplasma pneumoniae and Chlamydia pneumoniae. However, some research suggests that patients with mild-to-moderate community-acquired pneumonia may be successfully treated with 7 days or less of antibiotics. The shorter treatment may increase patient tolerance, and improve the likelihood of adherence to the treatment regimen, as well as help limit the growing problem of antibiotic resistance.

For a more detailed discussion of the different types of antibiotics, see the "Antibiotic Classes" section below.

Many cases of community-acquired pneumonia are caused by S. pneumoniae -- Gram-positive bacteria that usually respond to antibiotics known as beta-lactams (which include penicillin), and to macrolides. However, resistant strains of S. pneumoniae are increasingly common. Most resistant strains respond to fluoroquinolines such as levofloxacin (Levaquin), gemifloxacin (Factive) or moxifloxacin (Avelox), or to ketolides (telithromycin). Another common cause of community-acquired pneumonia is H. influenzae.

In addition, other important causes of CAP, particularly in younger people, are atypical bacteria, which respond to macrolides (erythromycin, clarithromycin, or azithromycin), ketolides, or newer fluoroquinolones.

Antibiotic treatment for CAP is determined by a number of factors, including:

  • The patient's history of antibiotic therapy
  • Co-existing diseases (such as COPD, diabetes, and heart failure)
  • Whether the patient is well enough to be treated at home or requires hospitalization or nursing home care.

Treatment options can include a single drug, such as levofloxacin or doxycycline, or combination treatment, such as a macrolide administered with a beta-lactam.

Antibiotics taken by mouth are generally sufficient for patients whose CAP is mild enough to be treated at home. Intravenous antibiotics are required for hospitalized patients with CAP. Antibiotic therapy should be given for a minimum of 5 days -- longer if the patient still has a fever and more than one sign of clinical instability.

Antibiotic Treatments for Hospital-Acquired (Nosocomial) Pneumonia

A broad range of antibiotics are available for the treatment of hospital-acquired pneumonias. Factors that may determine the choice of an antibiotic include:

  • Immune status
    • Patterns of antibiotic resistance within a particular hospital or community
  • Recent antibiotic usage
  • Specific organism identified
  • Use of ventilators

Antibiotics for P. Jiroveci Pneumonia (Common in HIV-Positive Patients)

Trimethoprim-sulfamethoxazole is the first choice for both preventing and treating P. Jiroveci (formerly called P. carinii) pneumonia in HIV-positive patients. Clindamycin-primaquine may be used in patients who do not respond to standard therapies.

A study of children with leukemia found atovaquone to be an excellent alternative for preventing P. jiroveci pneumonia in children who cannot tolerate trimethoprim-sulfamethoxazole, the current standard preventive therapy.

Treatment of Viral Infections

There are not as many choices for treating viral pneumonia. Oseltamivir (Tamiflu) and zanamivir (Relenza) are the recommended drugs for influenza A or B infections. Their use is only recommended if they are started in the first 48 hours of symptoms. Taken early, these medications may be effective in reducing symptoms and reducing the duration of illness.

Patients with viral pneumonias are at risk for what are called "superinfections," which generally refers to a secondary bacterial infection, usually caused by S. pneumoniae, S. aureus, or H. influenzae. Doctors most commonly recommend treatment with amoxicillin-clavulanate, cefpodoxime, cefprozil, cefuroxime, or a respiratory fluoroquinolone.

Patients with pneumonia caused by varicella-zoster and herpes simplex viruses are usually admitted to the hospital and treated with parenteral acyclovir intravenously for 7 days.

No antiviral drugs have been proven effective in adults with RSV, parainfluenza virus, adenovirus, metapneumovirus, the SARS coronavirus, or hantavirus. Treatment is largely supportive, with patients receiving oxygen and ventilator therapy as needed.

Treatment of RSV in Children. Ribavarin is the first treatment approved for RSV pneumonia, although it has only modest benefits. The American Academy of Pediatrics recommends this drug for children who are at high risk for serious complications of RSV.

Side Effects of Antibiotics

Most antibiotics have the following side effects (although specific antibiotics may have other side effects or fewer of the standard ones):

  • Allergic reactions (most commonly with medications derived from penicillin or sulfa). These reactions can range from mild skin rashes to rare but severe -- even life-threatening -- anaphylactic shock.
  • Infection with Clostridium difficile, a pathogen responsible for causing severe diarrhea, colitis, and abdominal pain (with overuse of antibiotics). This condition can be fatal.
  • Interactions with certain drugs, including some over-the-counter (OTC) medications. Patients should inform their physician of all medications and OTC preparations they are taking and of any drug allergies they might have.
  • Stomach problems (most common side effect).
  • Vaginal infections. Taking acidophilus supplements or eating yogurt with active acidophilius cultures may help restore healthy bacteria that offset the risk for such infections.

In-Depth From A.D.A.M. Surgery

Although most patients with pneumonia do not need invasive therapy, it may be necessary in patients with abscesses, empyema, or certain other complications.


Thoracotomy is the standard surgery for pneumonia. It requires general anesthesia and an incision to open the chest and view the lungs. This procedure allows the surgeon to remove dead or damaged lung tissue. In severe cases, the entire lobe of the lung is removed. This is called a lobectomy. Remaining healthy lung tissue re-expands after surgery to make up for tissue that has been removed.

Chest Tubes

Chest tubes are used to drain infected pleural fluid. Tubes are not typically required for pneumonia or abscesses. The tubes are inserted after the patient is given a local anesthetic. They remain in place for 2 - 4 days, and are removed in one quick movement. This can be very distressing, although some patients experience no discomfort. Complications of chest tubes include:

  • Accidental injury of the lung
  • Fluid build-up within the lung if the pleural fluid is removed too rapidly
  • Infection
  • Perforation of the diaphragm

Removing the chest tubes may cause the lung to collapse, requiring the reintroduction of a chest tube to inflate the lung.

In-Depth From A.D.A.M. Prevention

The best way to prevent serious respiratory infections such as pneumonia is to avoid sick people (if possible), and to practice good hygiene.

Good Hygiene and Preventing Transmission

Colds and flu are spread primarily from infected people who cough or sneeze. A very common method for transmitting a cold is by shaking hands. Research has found that washing hands frequently can prevent the spread of viral respiratory illnesses. Always wash your hands before eating and after going outside. Using ordinary soap is sufficient. Alcohol-based gels are also effective for everyday use, and may even kill cold viruses. If extreme hygiene is required, alcohol-based rinses are needed.

Antibacterial soaps add little protection, particularly against viruses. In fact, one study suggests that common liquid dishwashing soaps are up to 100 times more effective than antibacterial soaps in killing respiratory syncytial virus (RSV). Wiping surfaces with a solution that contains one part bleach to 10 parts water is very effective in killing viruses.

Changing Hospital Practices

Bacteria abound in hospitals and long-term care facilities, and are particularly virulent in areas with the sickest patients, such as intensive care units. Health care facilities are revising many of their practices and educating physicians, nurses, and therapists how to reduce the likelihood of transmitting bacteria.


Viral Influenza Vaccines (Flu Shot)

Description of Vaccines. Vaccines against the flu (or a "flu shot") use inactivated (not live) viruses. They are designed to provoke the immune system to attack antigens contained on the surface of the virus. Antigens are foreign molecules that the immune system specifically recognizes and targets for attack.

Timing and Effectiveness of the Vaccine. Ideally, people should get a flu shot every October or November. However, it may take longer for a full supply of the vaccine to reach certain locations. In such cases, the high-risk groups should be served first.

Children Who Should Be Vaccinated. The American Academy of Pediatrics (AAP) and the CDC recommend flu shots for all healthy children 6 - 59 months of age, as well as adults who are in regular contact with these children. The flu shot is not approved for children younger than 6 months of age.

Children who are receiving long-term aspirin therapy should also be immunized against the flu, because they are at higher risk for Reye syndrome, a life-threatening disease, if they get the flu.

Children with Asthma. Recent and major studies have found that the flu shot is safe for children with asthma. It is very important for these patients to reduce their risk for respiratory diseases. Unfortunately, 90% of asthma patients remain unvaccinated.

Older Children and Adults Who Should Be Vaccinated. The following, in order of priority, are the population groups who should be vaccinated each year. The first two groups have the highest need for influenza vaccinations and are given top priority:

  • All adults age 65 and older. Older adults who receive a flu shot have lower hospitalization rates than those who don't. Evidence now suggests that vaccination may help protect against adverse heart events (including after heart surgeries), stroke, and death from all causes in the elderly. Still, studies suggest that only two-thirds of people in this group are vaccinated, mostly because of unwarranted fears of ineffectiveness or adverse effects.
  • People of any age at high risk for serious complications from influenza. Such people include those with heart disease, lung problems, immune deficiencies, diabetes, kidney disease, or chronic blood disease. While there have been concerns about the safety of the vaccinations in certain high-risk patients, such as those with HIV or asthma, studies now suggest that the vaccine is generally safe in these patient groups. Furthermore, their risk for serious complications from influenza outweighs any potential adverse effects from the vaccines.
  • Adults ages 50 - 64 with chronic medical conditions. The US Advisory Committee on Immunization Practices (ACIP) suggests that all adults over age 50 be vaccinated, although this is not a recommendation of the CDC.

Other adults who should consider influenza vaccinations include:

  • People at risk for flu complications who are traveling to the tropics at any time or to the Southern Hemisphere between April and September.
  • Pregnant women at risk for flu complications who will be in their second or third trimester during flu season. (Vaccinations should usually be given after the first trimester.)
  • Health care providers with direct patient contact, child care providers, and residents of long-term care facilities.


Although some research supports the use of vitamin C for the prevention and treatment of pneumonia, most research says it's too early to recommend vitamin C supplements for the general population. These supplements may be helpful for pneumonia patients who are deficient in the vitamin, however.

Pneumococcal Vaccines

The pneumococcal vaccine protects against S. pneumoniae bacteria, the most common cause of respiratory infections. There are two effective vaccines available:

  • 23-valent polysaccharide vaccine (Pneumovax, Pnu-Immune) for adults
  • 7-valent conjugate vaccine (Prevnar or PCV7) for infants and young children.

Experts are now recommending that more people, including healthy elderly people, be given the pneumococcal vaccine, particularly in light of the increase in antibiotic-resistant bacteria.

Pneumococcal Vaccine in Young Children. The pneumococcal vaccine (Prevnar or PCV7) is very effective in children. Routine vaccination with the PCV7 vaccine began in 2000. In the first 3 years of its use, the vaccine cut pneumonia-related hospital admissions in children under age 2 by nearly 40%. Possibly due to "herd immunity," pneumonia-related hospital admissions in adults ages 18 - 39 also dropped by more than 25% during that time period.

Evidence suggests that this vaccination, plus the vaccination against Haemophilus influenzae (an important cause of meningitis), have led to 25,000 fewer cases of serious bacterial infections each year.

The pneumococcal vaccine is now recommended by many experts for the following groups:

  • All children up to age 2. The pneumococcal conjugate vaccine (Prevnar or PCV7) has now been added to the Recommended Childhood Immunization Schedule. The pneumococcal vaccine (Prevnar or PCV7) is very effective in children. Studies are suggesting that it prevents common ear infections, as well as serious infections such as pneumonia. In one study, a similar vaccine under investigation not only protected children in day care from serious respiratory infections, but also helped lead to fewer infections in their younger unvaccinated siblings.
  • Children up to age 5 who are at risk for pneumonia or complications of influenza, such as those with sickle-cell disease, immune deficiencies, or chronic medical conditions.
  • Other children aged 2 - 5 who are higher risk for serious pneumococcal infections should be considered for pneumococcal polysaccharide vaccination. They include African-Americans, Native Americans, children in group child care, socially or economically disadvantaged children, or those who have had frequent or complicated acute middle ear infections within the past year. (In one study, the vaccine reduced the number of ear infection episodes by 6%.)

The recommended schedule of immunization for Prevnar (PCV7) is four doses, given at 2, 4, 6, and 12 - 15 months of age. Infants starting immunization between 7 and 11 months should have three doses. Children starting their vaccinations between 12 and 23 months only need two doses. Those who are over 2 years old need only one dose.

Pneumococcal Polysaccharide Vaccine in Older Children and Adults. The pneumococcal polysaccharide vaccine is proving to help reduce the rate of pneumonia in young adults, although not to the degree that it protects young children. Its benefits for the elderly are unclear. Although it may not prevent community-acquired pneumonia, the vaccine might improve the outcome for older adults who develop the disease by reducing the risk of death and admission to an intensive-care unit.

Still, pneumonia is declining among adults, which may be due to fewer infections transmitted from vaccinated young children. Many experts now recommend the vaccine for the following older children or adults:

  • All people over age 65. (Anyone vaccinated more than 5 years previously should be revaccinated.) The vaccination is protective against pneumococcal bacteremia (blood infection) in this group, but it does not appear to protect against community-acquired pneumonia itself.
  • Adults with any chronic condition that increases the risk for pneumonia. This includes patients with heart disease, chronic lung disease (COPD or emphysema, but not asthma), or diabetes.
  • Individuals with immune deficiencies, such as HIV, or those undergoing treatments to suppress the immune system.
  • Patients with autoimmune diseases, such as rheumatoid arthritis and lupus. Unfortunately, studies suggest the vaccine may not be as effective in these patients as it is in those with healthy immune systems. Nevertheless, they are at high risk for serious respiratory infections and should be vaccinated.
  • Patients with kidney disease or kidney transplants. Older people who have had transplant operations or those with kidney disease may require a revaccination after 6 years.
  • Patients with problems in the spleen.
  • Alcoholics (especially those with cirrhosis).
  • People living in long-term care facilities.
  • Alaska Natives or Native Americans who may be at increased risk for pneumonia.

Because the vaccine is inactive, it is safe for pregnant women and people with immune deficiencies. In fact, when the vaccine is administered to pregnant women, it may actually protect their infants against certain respiratory infections.

Protection lasts for more than 6 years in most people, although it may wear off faster in elderly people than in younger adults. Anyone at risk for serious pneumonia should be revaccinated 6 years after the first dose, including those who were vaccinated before age 65. Subsequent booster doses, however, are not recommended.

Preventing Respiratory Syncytial Virus (RSV) Pneumonia in Children

Prevention of RSV. Two medications have been approved for protecting high-risk children against RSV pneumonia:

  • Palivizumab (Synagis) is known as a monoclonal antibody, a genetically engineered antibody that targets the RSV virus. It is given by an injection into the muscle. Early studies of motavizumab, another monoclonal antibody in development, also show potent protection against RSV.
  • RSV immune globulin (RespiGam) is made up of antibodies to RSV that are obtained from the blood of healthy infants. RespiGam is given as a shot.

In-Depth From A.D.A.M. References

American Academy of Pediatrics Committee on Infectious Diseases. Recommended immunization schedules for children and adolescents -- United States, 2008. Pediatrics. 2008;121:219-220.

Barr CE, Schulman K, Iacuzio D, Bradley JS. Effect of oseltamivir on the risk of pneumonia and use of health care services in chidlren with clinically diagnosed influenza. Curr Med Res Opin. 2007;23(3):523-531.

Chan EY, Ruest A, Meade MO, Cook DJ. Oral decontamination for prevention of pneumonia in mechanically ventilated adults: systematic review and meta-analysis. BMJ. 2007. Mar 26; [Epub ahead of print].

Christ-Crain M, Soltz D, Bingisser R, et al. Procalcitonin guidance of antibiotic therapy in community-acquired pneumonia. Am J Respir Crit Care Med. 2006;174:84-93.

Galobardes B, McCarron P, Jeffreys M, Davey-Smith G. Medical history of respiratory disease in early life relates to morbidity and mortality in adulthood. Thorax. 2008;Epub.

Gleason PP, Shaughnessy AF. STEPS new drug reviews telithromycin (Ketek) for treatment of community-acquired pneumonia. Am Fam Physician. 2007;76.

Grijalva CG, Nuorti JP, Arbogast PG, Martin SW, Edwards KM, Griffin MR. Decline in pneumonia admissions after routine childhood immunisation with pneumococcal conjugate vaccine in the USA: a time-series analysis. Lancet. 2007;369:1179-1186.

Hemilä H, Louhiala P. Vitamin C for preventing and treating pneumonia. Cochrane Database Syst Rev. 2007(1):CD005532.

Huggett JF, Taylor MS, Kocjan G, Evans HE, Morris-Jones S, Gant V, et al. Development and evaluation of a real-time PCR assay for detection of Pneumocystis jirovecii DNA in bronchoalveolar lavage fluid of HIV-infected patients. Thorax. 2008; 63:154-159.

Johnstone J, Marrie TJ, Eurich DT, Majumdar SR. Effect of pneumococcal vaccination in hospitalized adults with community-acquired pneumonia. Arch Intern Med. 2007;167:1938-1943.

Lawrence SJ, Puzniak LA, Shadel BN, Gillespie KN, Kollef MH, Mundy LM. Clostridium difficile in the intensive care unit: epidemiology, costs, and colonization pressure. Infect Control Hosp Epidemiol. 2007;28(2):123-130.

Lee TA, Weaver FM, Weiss KB. Impact of pneumococcal vaccination on pneumonia rates in patients with COPD and asthma. J Gen Intern Med. 2007;22(1):62-67.

Li JZ, Winston LG, Moore DH, Bent S. Efficacy of short-course antibiotic regimens for community-acquired pneumonia: a meta-analysis. Am J Med. 2007;120:783-790.

Limper AH. Overview of Pneumonia. In: Goldman L, Ausiello D. Goldman: Cecil Medicine. Philadelphia, Pa: Saunders; 2007:chap 97.

Lutfiyya MN, Henley E, Chang LF. Diagnosis and treatment of community-acquired pneumonia. Am Fam Physician. 2006;73:442-450.

Madden RM, Pui CH, Hughes WT, Flynn PM, Leung W. Prophylaxis of Pneumocystis carinii pneumonia with atovaquone in children with leukemia. Cancer. 2007. Mar 7; [Epub ahead of print].

Mandell LA, Wunderink RG, Anzueto A, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. 2007;44:S27-S72.

Muller B, Harbath S, Stolz D, et al. Diagnostic and prognostic accuracy of clinical and laboratory parameters in community-acquired pneumonia. BMC Infect Dis. 2007;7:10.

Neuman MI, Willett WC, Curhan GC. Vitamin and micronutrient intake and the risk of community-acquired pneumonia in US women. Am J Med. 2007;120:330-336.

Nisar N, Guleria R, Kuman S, Chand Chawla T, Ranjan Biswas N. Mycoplasma pneumoniae and its role in asthma. Postgrad Med J. 2007;83:100-104.

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Spaude KA, Abrutyn E, Kirchner C, Kim A, Daley J, Fisman DN. Influenza vaccination and risk of mortality among adults hospitalized with community-acquired pneumonia. Arch Intern Med 2007;167(1):53-59.

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