C-221. Real-Time PCR Detection of Pneumocystis jiroveci in the Immunocompetent Host Population

T. Grys, M. Binnicker, D. Maldonado, D. Midthun, A. Limper, N. Wengenack, J. Wilson;
Mayo Clin., Rochester, MN.

Background: Pneumocystis jiroveci is a ubiquitously distributed fungus that can cause severe respiratory disease in the immunocompromised host. In contrast, colonization with P. jiroveci rarely manifests clinically in the immunocompetent population. The conventional laboratory methods to identify P. jiroveci have included microscopic examination of respiratory smears and stained-tissue specimens. Microscopic examination provides a highly specific means to identify P. jiroveci, but lacks sensitivity. The recent application of real-time PCR technology has significantly improved the sensitivity of detection, while maintaining a high specificity for the organism. However, P. jiroveci has been detected in patients (typically immunocompetent) without evidence of active pulmonary pneumocystosis. Therefore, the high sensitivity of real-time PCR assays used to detect P. jiroveci may lead to false-positive declarations of disease. The goal of this study was to examine the P. jiroveci PCR positivity rate in an immunocompetent host population. Methods: The study enrolled immunocompetent patients undergoing bronchoscopy for a non-infectious indication (eg., neoplasm). A blood sample was collected to determine HIV status. A bronchoalveolar lavage (BAL) was performed during bronchoscopy, and the BAL fluid was examined for P. jiroveci using a KOH/calcofluor white stain and real-time PCR. Results: To date, 32 patients have been enrolled in the study and BAL fluid from 32/32 (100%) have tested negative for P. jiroveci by both smear and PCR. Conclusion: These results suggest that a positive PCR in a patient with pulmonary symptoms may be indicative of P. jiroveci infection, and not due to benign colonization with the organism. The findings of this ongoing study will serve to aid in the interpretation of P. jiroveci PCR results as the assay is fully implemented for the laboratory diagnosis of Pneumocystis disease.