Detection of Pneumocystis carinii in rats by polymerase chain reaction: comparison of lung tissue and bronchoalveolar lavage specimens.

The purpose of this study was to determine and compare the efficiency of detection of Pneumocystis carinii in rats by polymerase chain reaction (PCR) of DNA extracted from two sampling locations: lung tissue and bronchoalveolar lavage. The study involved naturally infected F344 rats that were allotted to groups to intercollate the investigation of several variables, including nonimmunosuppressed rats, rats subjected to a timed induction sequence of 1 to 4 weeks of immunosuppression, and two immunosuppressants: a corticosteroid and cyclophosphamide. The PCR amplified a 357-base pair region contained within the gene encoding the large ribosomal RNA subunit of P. carinii mitochondrial DNA. The identity of the PCR product was confirmed by Southern blot analysis with an oligonucleotide probe. In a comparison of lung bronchoalveolar lavage specimens after immunosuppression, P. carinii was detected by PCR in 100% of lung tissue but in only 87.5% of the lavage specimens. Lung tissue of three animals was test-positive when the corresponding lavage specimen was negative by PCR analysis. The PCR detected P. carinii in both types of specimens from the same two of three nonimmunosuppressed rats. In all there was 88% agreement of PCR results between the two sampling techniques. The difference in diagnostic outcome for the two specimen types was not statistically significant (Fisher's exact test). It was concluded that both specimen types were adequate for PCR detection of P. carinii in rats.