Hospital-Acquired and Institutional-Acquired Pneumonia
Pneumonia that is acquired in the hospital or another type of institution tends to be far more severe than pneumonia acquired in the community. The organisms in these institutions 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.
Staphylococcal Pneumonia: Staphylococcus aureus causes only 2% of community-acquired pneumonias, but it causes 10 to 15% of hospital-acquired pneumonias. This type of pneumonia is most likely to occur while people are hospitalized for another disorder, and it tends to develop in the very young, the very old, and people who are already debilitated by other illnesses. It also tends to occur in alcoholics. Although uncommon, it is serious--the death rate is about 15 to 40%--in part because those who develop staphylococcal pneumonia are usually already seriously ill.
Staphylococcus causes typical pneumonia symptoms, but the chills and fever are more persistent in staphylococcal pneumonia than in pneumococcal pneumonia. Sometimes the symptoms worsen rapidly, with severe and potentially fatal deterioration in lung function. Staphylococcus may occasionally cause collections of pus (abscesses) in the lungs and, in children, may produce lung cysts that contain air (pneumatoceles). Bacteria may be carried from the lung by the bloodstream and produce pus elsewhere. Collections of pus in the pleural space (empyema) are relatively common (see Section 4, Chapter 52). These collections are drained using a needle or a chest tube.
Antibiotics that are active against Staphylococcus, usually a type of penicillin called oxacillin or nafcillin or the equivalent, are started as soon as possible. However, more and more strains of Staphylococcus are becoming resistant to these penicillins, requiring the use of other antibiotics, such as vancomycin.
Gram-negative Bacterial Pneumonia: Gram-negative bacteria, such as Klebsiella (Friedländer's pneumonia), Pseudomonas, Enterobacter, Proteus, Serratia, and Acinetobacter, cause pneumonia that tends to be serious.
Gram-negative bacterial pneumonias almost always occur only in people who are hospitalized or who live in nursing homes; they rarely infect the lungs of healthy adults. Gram-negative bacteria are particularly common causes of pneumonia in people who are on ventilators (breathing machines used in intensive care units). Other people at risk are infants, older people, alcoholics, and people with chronic diseases, especially immune system disorders.
The symptoms of gram-negative bacterial pneumonia are the same as for gram-positive pneumonia, except that people tend to be sicker and worsen quickly. Gram-negative bacteria may rapidly destroy lung tissue, so gram-negative pneumonia tends to become serious quickly. Fever, coughing, and shortness of breath are common. The coughed-up sputum may be thick and red--the color and consistency of currant jelly.
Because of the seriousness of the infection, the person is treated intensively in the hospital with antibiotics, supplemental oxygen, and intravenous fluids. Sometimes the person must be put on a ventilator. Despite receiving excellent treatment, about 25 to 50% of people with gram-negative pneumonia die.
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