Pneumocystis carinii in human lungs at autopsy.

To get some information about the prevalence of Pneumocystis carinii in the Danish population we have examined autopsy lung biopsies from patients at 2 large hospitals in Copenhagen, Righospitalet (RH) and Finseninstituttet (F), in a 5-year period from 1979 to 1984. Imprints made from the biopsies were stained with the toluidine blue O method and examined microscopically for pneumocysts. A total of 1762 patients were examined and pneumocysts found in 83 (4.7%); at RH 54 (4.9%) of 1106 patients and at F29 (4.4%) of 656 patients. A possible influence of certain climatic factors on the prevalence of pneumocysts in humans was shown: low temperature, low vapour pressure and low relative humidity seem to be correlated with low prevalence of pneumocysts. The general use of trimethoprim-sulfamethoxazole in the hospitals may possibly influence the prevalence of pneumocysts: the amount requested in the period of the investigation is negatively correlated with the prevalence of pneumocysts.