Pneumocystis carinii cysts are susceptible to inactivation by chemical disinfectants.

The inactivation efficacy of eight disinfectants commonly used in laboratories and animal rooms to inactive Pneumocystis carinii cysts was estimated by experimental infection in C.B-17-scid mice. The disinfectants examined in this study were 70% ethyl alcohol, 10% iodoform, 0.5% hypochlorous acid, two 1% quanternary ammonium salts, 3% hydrogen peroxide, sodium chlorite and 1% cresol soap. The lung homogenates from P. carinii infected C.B-17-scid mice were treated with each disinfectant for 15 min at room temperature, washed with saline, and inoculated into C.B-17-scid mice. Eight weeks after inoculation, lungs from these mice were examined by staining with toluidine blue O to detect P. carinii cysts. PCR amplifying 346 bp of P. carinii specific mitochondrial ribosomal RNA large segments was also performed using DNA extracted from the lungs of the mice. As a result, seven disinfectants, excepting for 0.5% hypochlorous acid, were effective in the inactivation of P. carinii cysts. These results suggest that P. carinii cysts were sensitive to chemical disinfectants even though they have been commonly considered as insensitive.