Search for Pneumocystis carinii DNA in upper and lower respiratory tract of humans

Recent studies suggest that Pneumocystis carinii DNA may be detected by PCR in oropharyngeal secretions in the majority of patients with P. carinii pneumonitis (PCP). However, the prevalence of P. carinii DNA in patients without PCP has not been well established. A prospective study of 258 nasal, pharyngeal, and salivary specimens from 86 individuals with AIDS, cancer or no underlying disease, and without respiratory infection, found no P. carinii DNA in any of the samples. Separately, to validate the PCR for detection of P. carinii DNA, 45 specimens from the lower respiratory tract (bronchoalveolar lavage [BAL] and sputum) from 31 patients with pneumonitis and AIDS or cancer were studied. Eleven had PCP by conventional stains and 20 did not. All patients with PCP, and none without PCP, had P. carinii DNA in BAL, sputum or both. The study indicates the prevalence of P. carinii DNA is low or absent in oropharyngeal secretions in the absence of PCP.