Pulmonary Colonization with Pneumocystis cariniiin Human Immunodeficiency Virus-Negative Patients: Assessing Risk with Blood CD4+ T Cell Counts

Use of PCR analysis has led to detection of low numbers of Pneumocystis carinii organisms, which were undetectable by microscopy, in bronchoalveolar lavage (BAL) fluid specimens from immunosuppressed patients who showed no evidence of acute P. carinii pneumonia (PCP) [1]. These low levels of parasites were usually considered to reflect pulmonary colonization, but their significance was a subject of controversy. Cases of colonization were described mainly in patients positive for HIV who had blood CD4+ T cell counts of <400 × 106/L [2]. There were little data concerning HIV-negative patients [3].This study investigates the presence of P. carinii DNA in BAL fluid specimens from HIV-negative patients with no evidence of PCP and examines the link between colonization and decreases in blood CD4+ T cell counts in this patient population. Eighty-two HIV-negative adult patients were admitted to our hospital during 1 year who underwent BAL for disease investigation; all were enrolled in the study. BAL fluid specimens were regularly sent to our laboratory for detection of P. carinii. After cytocentrifugation, Giemsa staining, and immunofluorescence (Diagnostics Pasteur, Paris), specimens were examined by microscope. BAL sediment was assayed by Heminested PCR; the specific primers pAZ102-H, pAZ102-E, and pAZ102-L2 were used to amplify the gene encoding the mitochondrial large subunit rRNA [1, 4]. Results of PCR analysis were not used to determine patient management, but patients were followed up to detect the occurrence of PCP. Clinical data and CD4+ and CD8+ T cell counts were obtained retrospectively.