Hospital-acquired pneumonia develops in people who have been hospitalized, typically after about 2 days or more of hospitalization. Institution-acquired pneumonia develops in people who reside in nursing homes or who have contact with medical settings, such as dialysis centers.
One reason that pneumonia acquired in the hospital is more severe is that the infecting organisms tend to be more aggressive and harder to treat. Additionally, people in hospitals and nursing homes tend to be sicker even without pneumonia than those living in the community and therefore are not as able to fight the infection.
People who are hospitalized and seriously ill, especially if they require assistance in breathing from a mechanical ventilator, are at greatest risk of acquiring pneumonia. Other risk factors include previous antibiotic treatment and coexisting illness such as heart, lung, liver, or kidney dysfunction. People who are older than 70, have had abdominal or chest surgery, take proton pump inhibitors, or have a combination of these factors are at particularly high risk.
People who are debilitated, such as those living in nursing homes, are also at risk.
Organisms that do not normally cause pneumonia in healthy people can cause pneumonia in people who are hospitalized or debilitated. Many such people have an immune system that is not able to resist even mild infectious challenges. The most likely organisms depend on what organisms are prevalent in the hospital and sometimes depend on what other illnesses the person has.
Hospital-acquired pneumonia is more likely than community-acquired pneumonia to be caused by Staphylococcus aureus or a gram-negative bacterium, such as Klebsiella pneumoniae or Pseudomonas aeruginosa. Sometimes pneumonia is caused by Legionella or methicillin-resistant Staphylococcus aureus (MRSA, the super-bug).
Symptoms are generally the same as those for community-acquired pneumonia: a general feeling of weakness (malaise), cough, shortness of breath, and chest pain. Pneumonia in critically ill people, especially those who are on a mechanical ventilator, causes fever and increases the respiratory rate and the heart rate.
Pneumonia acquired in an institutional setting may be more difficult for doctors to recognize than pneumonia acquired in other settings. For example, many people in institutional settings who develop pneumonia, such as the elderly, those with breathing tubes who are receiving mechanical ventilation, and those with dementia, may be unable to describe symptoms such as chest pain, shortness of breath, and weakness.
Hospital-acquired and institution-acquired pneumonia is suspected on the basis of a person's symptoms. The diagnosis is confirmed with a chest x-ray. Blood tests are done. However, these methods are not always accurate. Also, because people may be very sick, doctors may need to identify the organism that is causing pneumonia so that they can determine the best treatment. For these reasons, sometimes doctors use bronchoscopy to confirm pneumonia and obtain a sputum specimen 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 a solution, which can then be retrieved for analysis (bronchoalveolar lavage).
Treatment 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. Because of the seriousness of the infection, people in nursing homes are often treated in the hospital. People who are seriously ill may be placed in an intensive care unit and sometimes put on a ventilator. Treatments include intravenous antibiotics, supplemental oxygen, and intravenous fluids. There are several drugs that can be used, including the following:
These drugs are given alone or combined with vancomycin. If MRSA is suspected, an antibiotic called linezolid may be used.
Because some people who live in nursing homes are very ill, pneumonia can be extremely serious. In order to treat pneumonia with the most powerful treatments available, doctors usually have nursing home residents transferred to a hospital. However, pneumonia is often fatal despite such treatment, and the treatment itself may be difficult to tolerate, especially if a mechanical ventilator is needed. 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 when they enter a nursing home.
Despite receiving excellent treatment, about 25 to 50% of people who develop hospital-acquired pneumonia die. Whether the cause of death is due to underlying illness or to the pneumonia itself can be difficult to tell.
Last full review/revision April 2008 by John G. Bartlett, MD