Changing spectrum of causative organisms of pneumonia acquired out of hospital during a ten-year period (1982-1992)

Background and objective: The picture of pneumonia acquired out of hospital is continually changing. Microbial aetiology as well as predisposing factors, course and prognosis of this disease were prospectively analysed over a period of 10 years. Patients and methods: In three prospective studies, undertaken between 1982 and 1992, data from 448 patients with out-of-hospital acquired pneumonia were analysed. Microbiological evidence was obtained through blood cultures, from purulent sputum or bronchial secretions, as well as by determining serum antibodies or antigens in urine. Results: Proof of causative organism was achieved in 282 patients (64.1 %), with identification of 337 different ones. The spectrum of causative microbes shifted during the study period from predominantly grampositive bacteria to largely atypical organisms (from 12.5 % during 1982/1983, to 36.7 % in 1991/1992). Although pneumococci continued to dominate, Chlamydia pneumoniae appeared as an important cause of pneumonia, at 11.4 % the most important atypical organism in 1991/1992. - Most patients (74.3 %) had a chronic underlying disease. The death rate remained relatively constant at 12.9 % during the 10-year period. Conclusion: The observed changes in microbial spectrum should be taken into account when specific antibiotic treatment is given. History as well as clinical, radiological and laboratory findings are of only limited Value as pointers to the possible microbial cause.