[Etiology of pneumonia and host defense]

To investigate the relationship of efficacy of chemotherapy to host defense, we reviewed the clinical features, treatment and outcome in 648 patients with acute pneumonia (424 males and 224 females; mean age, 65 years) treated between 1984 and 1989. Pneumonia complicated pulmonary disease in 336 patients (52%) and complicated systemic disease in 258 (40%). Pneumonia pathogens were diagnosed in 346 patients (53%); the five major pathogens were S. pneumoniae (19%), H. influenzae (16%), S. aureus (14%), K. pneumoniae (14%) and P. aeruginosa (11%). The incidence of K. pneumoniae infection were decreased from 18% to 3.5% and that of S. aureus increased from 10.9% to 26.3% during the study period. The incidence of S. aureus and of P. aeruginosa infection was much higher in patients with nosocomial pneumonia, systemic disease, or serum protein concentration under 6.5 g/dl. beta-lactamase antibiotics were administered to 70% of all patients, with an efficacy rate of 74.9% of after the first course of antibiotics therapy. The efficacy rate was decreased in patients with nosocomial pneumonia, systemic or pulmonary disease, or malnutrition. The data presented in this study indicate that the risk of pneumonia must be taken into careful consideration in patients with compromising complications.