Infectious pneumonias: a review.
Diplococcus pneumoniae remains the most frequent cause of community-acquired bacterial pneumonia. Other frequently isolated bacterial pathogens are Hemophilus influenzae, Klebsiella organisms, and Staphylococcus aureus. The etiologic agents most commonly implicated in hopsital-acquired pneumonias are gram-negative bacilli including E. coli, proteus organisms, and species of Klebsiella-Enterobacter, pseudomonas, and Serratia. Among older children and young-adults, Myocoplasma pneumoniae is a common cause of penumonia. Influenza is the most important cause of viral pneumonia in adults, but there is increasing concern about pulmonary infection due to adenoviruses. In those with a history of travel to endemic areas, the diagnosis of fungal pneumonia due to Histoplasma capsulatrum, Blastomyces dermatitides, or Coccidioides immitis, should be considered. Penumonias due to opportunistic fungi (including species of Candida, Aspergillus, and Phycomycetes) and higher bacteria such as Nocardia asteroides are also on the increase, and these arise mostly in compromised hosts. Treatment of pneumonia almost always must be started before culture results are known and in the overwhelming majority of cases, appropriate regimens can be selected after taking an adquate history, doing a careful physical examination, evaluating expectorated sputum for cells and organisms, and examining the chest x-ray. Although anti-infective agents are the mainstay of treatment for most infectious pneumonias, supportive therapy, including adequate tracheobronchial toilet, drainage of abscesses, oxygen inhalation, maintenance of adequate nutrition, and monitoring for super-infection and anti-infective side effects may be life-saving in certain situations.