Use of semiquantitative PCR to assess onset and treatment of Pneumocystis carinii infection in rat model.

The use of semiquantitative PCR (SQPCR) to assess Pneumocystis carinii pneumonia (PCP) infection and its response to treatment was studied with rats. Groups of eight rats were immunosuppressed with steroids for 3 to 12 weeks. Untreated controls were maintained for the same periods. Three groups of rats were treated with pentamidine, three groups were treated with trimethoprim-sulfamethoxazole, and three groups of rats were tapered from steroids. At various times during suppression, rats from the different groups were sacrificed. At necropsy, lungs were lavaged to obtain bronchoalveolar fluids and then homogenized. Bronchoalveolar fluids and homogenates were assayed by cyst counting and SQPCR. An increase in the SQPCR signal was seen throughout immunosuppression, with a slow decrease upon the withdrawal of steroids and a faster decrease with drug treatment. SQPCR results with lung homogenates and bronchoalveolar fluids strongly correlated with each other and with cyst counts. These results warrant investigation of SQPCR for assessing treatment results of human P. carinii pneumonia infection.