The value of routine microbial investigation in community-acquired pneumonia.

The way in which microbiological investigations are used in routine clinical practice and the value of such tests in directing antibiotic prescribing, was studied in adults admitted to hospital with a diagnosis of community-acquired pneumonia. One-hundred and twenty-two consecutive patients admitted to one teaching and one district general hospital were studied between April 1988 and March 1989. Blood cultures were performed in 81% of cases, sputum was examined in 45% and complete serological tests were performed in 28%. No causative pathogen was found in 74% of cases and results of microbial tests directed a change in antibiotic therapy in only 8% of cases. Routine microbial investigation of all adults admitted to hospital with community-acquired pneumonia is unhelpful and probably unnecessary. We suggest a strategy for microbial investigation linked to initial illness severity to replace the current haphazard approach.