DNA amplification from nasopharyngeal aspirates in rats: A procedure to detect Pneumocystis carinii

The diagnosis of P.carinii pneumonia (PCP) requires invasive methods of bronchoalveolar lavage, lung biopsy, or induced sputum. In this study, we examined efficacy of PCR compared to Giemsa and silver staining to detect P. carinii in easily accessible extrapulmonary sites as well as lung. Samples were collected from lung, nasal, pharyngeal, stomach aspirates, urine and, blood from dexamethasone treated or untreated Sprague-Dawley rats. All of the immunosuppressed lung samples were P. carinii positive by PCR, and staining. DNA sequences of P. carinii were found in 93% of nasal, 75% of pharyngeal aspirates and 0% of urine, blood or sera from immunosuppressed rats. No P. carinii cysts or trophozoites were found in nasopharyngeal aspirates by Giemsa and silver staining. None of the immunocompetent rats was PCR positive. In conclusion: PCR amplification products of nasopharyngeal aspirates showed that immunosuppressed rats can carry P. carinii fragments in their upper respiratory tracts and this suggests an approach to be investigated in humans with PCP.