Investigation of Pneumocystis jirovecii Infection and Colonization in Immunocompromised Patients with Pneumonia

Abstract

Pneumocystis jirovecii is an atypical fungus that causes P.jirovecii pneumonia (PCP) in immunocompromised patients. Currently, while the incidence of AIDS-related PCP is decreasing, PCP has become more common in HIV-negative immunosuppressive patients as a result of increased diseases requiring immunosuppressive therapy. In this study, it was aimed to investigate PCP and colonizations by microscopy, polymerase chain reaction (PCR) and Krebs von den Lungen-6 (KL-6) tests in symptomatic immunosuppressive inpatients with the sign of radiologically atypical pneumonia in Mersin University Hospital. A total of 96 patients, between August 2016 and February 2018 were included in the study. Seventy two (75%) of the 96 patients were under immunosuppressive therapy. P.jirovecii was investigated in the respiratory tract samples [sputum (n= 88), tracheal aspirate (n= 6) and bronchoalveolar lavage (n= 2)] by mtLSUrRNA nested PCR and microscopic staining methods [immunofluorescence assay (IFA), Toluidine Blue O (TBO)], and KL-6 levels were tested in serum samples. P.jirovecii was detected in 16 (16.7%) samples by PCR, in five (5.2%) samples by IFA, in three (3.1%) samples by TBO stain method. When IFA was taken as a reference test, sensitivity and specificity of TBO and PCR were calculated as 60% and 100%; 100% and 87.9%, respectively. In P.jirovecii PCR positive patients, the distribution of underlying diseases; cancer (n= 6), hematological malignancy (n= 3), HIV/AIDS (n= 3), COPD (n= 2), and interstitial lung disease (n= 2) were found as 11 (68.75%) of the 16 positive patients, received immunosuppressive therapy (HIV positive non-Hodgkin lymphoma); of the 3 (18.75%) patients of were immunocompetent, and only 2 (12.5%) were HIV/AIDS. Five of the 16 PCR positive the patients that have positive microscopic examination were definited PCP [HIV/AIDS (n= 3), lung cancer (n= 1), interstitial lung disease (n= 1)]; three patients were PCR positive and microscopy negative probable PCP [multiple myeloma (n= 1), interstitial lung disease (n= 1), cholangiocellular carcinoma (n= 1)] and eight other patients were identified as colonized. In the study, when the frequency of the detection of P.jirovecii was evaluated according to the underlying diseases, it was found statistically significantly higher only in HIV/AIDS patients (p= 0.012). When KL-6 was evaluated among the patients defined as PCP/possible PCP and colonization, sensitivity and specificity were determined as 62.5% and 75%, respectively. As a result, nested PCR method was found as sensitive and successful for the detection of P.jirovecii from sputum samples. KL-6 test was not found sufficient for the differentiation of colonization and the infection in PCR positive patients. The results obtained in the study showed that PCP should be on the differential diagnosis list according to the immune status and the clinical features of the inpatients. More researchs are required with more patients to achieve for detailed reliable results in these groups. In addition, molecular epidemiological studies related to genotyping and resistance against anti-PCP drugs are needed to understand P.jirovecii infections in our region and country.