DNA amplification of nasopharyngeal aspirates in rats: a procedure to detect Pneumocystis carinii

The diagnosis of Pneumocystis carinii pneumonia (PCP) requires invasive met hods of bronchoalveolar lavage and lung biopsy. In this study, we examined efficacy of polymerase chain reaction (PCR) compared to Giemsa and silver a mmoniacal staining to detect P. carinii in easily accessible extrapulmonary sites as well as lung. Samples were collected from lung, nasal and pharyng eal aspirates, gastric contents, urine and blood from dexamethasone treated or untreated virus-free Sprague-Dawley rats. All immunosuppressed lung sam ples were P. carinii positive by PCR analysis and both stains. Respectively DNA fragments of P. carinii were found in 93%, of nasal and 75% of pharyng eal aspirates, and 0% of sera, urine or gastric aspirates from immunosuppre ssed rats. However, no P. carinii cysts or trophozoites were found:in nasal and pharyngeal aspirates (extrapulmonary sites) by silver ammoniacal or Gi emsa staining. In comparison, none of the specimens: from immunocompetent r ats were PCR, positive at any sites tested including the lungs. Therefore, PCR amplification products of nasal and pharyngeal aspirates showed that im munosuppressed rats with PCP can carry P. carinii DNA fragments in their up per respiratory tracts, but immunocompetent animals without PCP, are free o f the organism and this suggests an approach to be investigated in humans w ith PCP. (C) 1999 Academic Press.