Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Hospital-Acquired Pneumonia


Sanjay Sethi

, MD, University at Buffalo SUNY

Last full review/revision Dec 2020| Content last modified Dec 2020
Click here for the Professional Version
Topic Resources

Hospital-acquired pneumonia is lung infection that develops in people who have been hospitalized, typically after about 2 days or more of hospitalization.

  • Many bacteria, viruses, and even fungi can cause pneumonia in people who are hospitalized.

  • The most common symptom is a cough that produces sputum, but chest pain, chills, fever, and shortness of breath are also common.

  • Diagnosis is based on a person’s symptoms and the results of x-rays or a computed tomography (CT) scan of the chest.

  • Antibiotics, antiviral drugs, or antifungal drugs are used, depending on which organism has most likely caused the pneumonia.

Pneumonia acquired in the hospital is usually more severe than pneumonia acquired in the community because the infecting organisms tend to be more aggressive. They are also less likely to respond to antibiotics (called resistance) and are, therefore, harder to treat. Additionally, people in hospitals tend to be sicker even without pneumonia than those living in the community and therefore are not as able to fight the infection.

(See also Overview of Pneumonia.)

Risk Factors of Hospital-Acquired Pneumonia

People who are hospitalized and seriously ill, especially if they have another illness that requires treatment with a breathing machine (mechanical ventilator), are at greatest risk of acquiring pneumonia. Other risk factors include

  • Previous antibiotic treatment

  • Coexisting illness such as heart, lung, liver, or kidney dysfunction

  • Age older than 70

  • Recent abdominal or chest surgery

  • Possibly the use of proton pump inhibitors (omeprazole, esomeprazole, lansoprazole, or pantoprazole) for treatment of gastroesophageal reflux disease

  • Debilitation

Organisms that do not normally cause pneumonia in healthy people can cause pneumonia in people who are hospitalized or debilitated because many of these people have an immune system that is less able to resist infection. The most likely organisms depend on what organisms are prevalent in the hospital and sometimes depend on what other illnesses the person has.

Causes of Hospital-Acquired Pneumonia

Hospital-acquired pneumonia is most commonly caused by the following bacteria:

MRSA, P. aeruginosa, and other gram-negative intestinal bacteria often are resistant to certain antibiotics.

Viruses and fungi are increasingly being recognized as causes of hospital-acquired pneumonia.

Symptoms of Hospital-Acquired Pneumonia

Symptoms are generally the same as those for community-acquired pneumonia:

  • A general feeling of weakness (malaise)

  • Cough that produces sputum (thick or discolored mucus)

  • Shortness of breath

  • Fever

  • Chills

  • Chest pain

Pneumonia acquired in the hospital may be more difficult for doctors to recognize than pneumonia acquired in the community. For example, many hospitalized people who develop pneumonia, such as older people, those with breathing tubes who are receiving mechanical ventilation, those with dementia, and those who are critically ill, may be unable to describe symptoms such as chest pain, shortness of breath, and weakness. In those cases, pneumonia is often suspected on the basis of fever and an increase in the respiratory rate and the heart rate.

Older people who have pneumonia may also have confusion, loss of appetite, restlessness and agitation, falling, and incontinence (an involuntary loss of urine).

Did You Know...

  • Pneumonia that is acquired in the hospital tends to be far more severe than pneumonia acquired in the community.

Diagnosis of Hospital-Acquired Pneumonia

  • A doctor's evaluation of symptoms

  • A chest x-ray or chest computed tomography (CT) scan

  • Sometimes blood cultures

  • Sometimes bronchoscopy or thoracentesis

The diagnosis of hospital-acquired pneumonia is based on a person’s symptoms and the results of a chest x-ray or a chest CT scan. Doctors usually take a sample of blood so they can try to grow (culture) the bacteria in the laboratory and identify it.

People who have hospital-acquired pneumonia may be very sick, so doctors may need to identify the organism that is causing pneumonia to determine the best treatment. For these reasons, sometimes doctors do bronchoscopy to obtain specimens from within the lung itself to try to identify the organism. During bronchoscopy, a flexible viewing tube is inserted into the trachea and lungs. Samples of pus, secretions, or even lung tissue can be collected for examination. If no secretions are visible, an area of the lung can be washed with fluid, which can then be retrieved for analysis (a procedure called bronchoalveolar lavage). If fluid has collected in the lining of the lung (called a pleural effusion), doctors may place a needle into the chest to collect this fluid for culture (a procedure called thoracentesis).

Prognosis of Hospital-Acquired Pneumonia

Despite receiving excellent treatment, a high percentage of people who develop hospital-acquired pneumonia die. However, death is often related to the underlying health problems that allowed the pneumonia to develop (for example, widespread cancer).


Spotlight on Aging: Pneumonia

Pneumonia occurs more commonly in older than in younger people, and it also tends to be more serious. In many older people, the infection spreads beyond the lungs.

Older people have weakened defenses against infection. The mechanisms that clear microorganisms from the airways are not as effective in older people as they are in younger people. Weakness may make coughing less vigorous. Aging also weakens the immune system. Older people at greater risk of developing pneumonia include those

  • Whose lungs have been damaged by smoking (smoking irritates the lining of the lungs and paralyzes the cells that normally sweep and cleanse the airways) or chronic obstructive pulmonary disease

  • Whose lungs have recently been irritated by a mild infection, such as a cold or, especially, influenza

  • Who have a poor cough reflex, for example, resulting from a previous stroke, or who are too weak (or who are in pain from recent surgery or an accident) to cough vigorously

  • Who are less able to fight off infections, including people who are undernourished

  • Who are taking certain drugs that weaken the immune system, such as corticosteroids

  • Who have certain diseases, such as heart failure or diabetes

  • Who have cancer in or near the airways of the lungs (the cancer may block the airways and trap any microorganisms that have reached the air sacs)

  • Who are paralyzed (for example, because of a spinal injury or stroke)

  • Who are not fully conscious (in part because they are unable to cough)

Infection with some of the microorganisms that cause pneumonia can be prevented with vaccinations. So doctors recommend that people who are 65 or older receive the pneumococcal vaccine. People younger than 65 who have medical conditions that make them at higher risk of developing pneumonia should also receive the vaccine. Doctors also recommend that older people in particular receive an annual influenza vaccine because the influenza virus can also cause or contribute to pneumonia.

Most older people who get pneumonia are treated in the hospital with intravenous antibiotics. Pneumonia can cause older people to get very sick very quickly, and older people tend to respond less well to oral antibiotics.

Treatment of Hospital-Acquired Pneumonia

  • Antibiotics

Treatment of hospital-acquired pneumonia is with antibiotics that are chosen based on which organisms are most likely to be the cause and the specific risk factors the person has. People who are seriously ill may be placed in an intensive care unit and sometimes put on a ventilator. Treatments include intravenous antibiotics, oxygen, and intravenous fluids.

These drugs are given alone or are combined.

End-of-life issues in serious pneumonia

Some people with hospital-acquired pneumonia are very ill. Pneumonia is often treated with strong antibiotics and, if needed, a mechanical ventilator. People who are expected to die soon may not wish to receive such aggressive treatment. People with severe or terminal disorders should discuss with their doctors and family members their wishes for treatment of pneumonia or other serious complications when they enter the hospital.

Drugs Mentioned In This Article

Generic Name Select Brand Names
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Test your knowledge

Air Pollution-Related Illness
Illnesses linked to air pollution are categorized as environmental lung diseases. Exposure to air pollution for an extended period may increase respiratory infections and symptoms of respiratory disorders, such as coughing. In which of the following groups is long-term exposure to air pollution especially likely to increase respiratory infections and symptoms of respiratory disorders?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID