[Community-acquired pneumonia].

: In a prospective study 212 patients were analysed who, between 1. 10. 1982-31.12. 1983 and 1. 10. 1985-31. 12. 1986, had been admitted to hospital because of pneumonia. The causative organism was identified in 127 of the 212 patients (60%). Pneumococcus was the most common organism (n = 64), as demonstrated by culture and immunological techniques of determining antigen or antibody. Next most common was Legionella (n = 15) of various species. Mixed infections were found in 11 patients, in all instances associated with pneumococci. There were 24 deaths (11.3%). It is concluded from these results that (1) determination of pneumococcal antigen in sputum, but not in urine or serum, can improve the identification of the causative organism; (2) Legionella is one of the most common causes of pneumonia acquired outside of hospital; and (3) adequate serological diagnosis of Legionnaire's disease is possible only if a large number of different species are tested for.