Pneumocystis carinii f. sp hominis DNA in immunocompetent health care workers in contact with patients with P-carinii pneumonia

The possible transmission of Pneumocystis carinii f. sp. hominis from patie nts with P. carinii pneumonia to asymptomatic health care workers (HCW), wi th or without occupational exposure to human immunodeficiency virus (HIV)-i nfected patients with P. carinii pneumonia, was examined. HCW in a speciali st inpatient HIV-AIDS facility and a control group in the general medical-r espiratory service in the same hospital provided induced sputum and/or nasa l rinse samples, which were analyzed for the presence of P. carinii f. sp. hominis DNA by using DNA amplification (at the gene encoding the mitochondr ial large subunit rRNA [mt LSU rRNA]). P. carinii f. sp. hominis DNA was de tected in some HCW samples; those with the closest occupational contact wer e more likely to have detectable P. carinii DNA. P. carinii DNA was detecte d in one HCW who carried out bronchoscopy over a 2-year period. P. carinii- positive samples were genotyped by using DNA sequence variations at the int ernal transcribed spacer (ITS) regions of the nuclear rRNA operon, along wi th bronchoalveolar lavage samples from patients with P. carinii pneumonia h ospitalized at the same time. Genotyping identified 31 different P. carinii f. sp. hominis ITS genotypes, 26 of which were found in the patient sample s. Five of the eight ITS genotypes detected in HCW samples were not observe d in the patient samples. The results suggested that HCW in close occupatio nal contact with patients who had P. carinii pneumonia may have become colo nized with P. carinii. Carriage was asymptomatic and did not result in the development of clinical disease.