Genetic diversity of Pneumocystis jirovecii from a cluster of cases of pneumonia in renal transplant patients: cross-sectional study.

Pneumocystis jirovecii can cause severe potentially life-threatening pneumonia (PCP) in kidney transplant patients. Prophylaxis of patients against PCP in this setting is usually performed during 6months after transplantation. The aim of this study is to describe the molecular epidemiology of a cluster of PCP in renal transplant recipients in Brazil. Renal transplant patients who developed PCP between May and December 2011 had their formalin-fixed paraffin-embedded (FFPE) lung biopsy samples analysed. Pneumocystis jirovecii 23S mitochondrial large subunit of ribosomal RNA (23S mtLSU-rRNA), 26S rRNA, and dihydropteroate synthase (DHPS) genes were amplified by polymerase chain reaction (PCR), sequenced, and analysed for genetic variation. During the study period, 17 patients developed PCP (only four infections were documented within the first year after transplantation) and six (35.3%) died. Thirty FFPE samples from 11 patients, including one external control HIV-infected patient, had fungal DNA successfully extracted for further amplification and sequencing for all three genes. A total of five genotypes were identified among the 10 infected patients. Of note, four patients were infected by more than one genotype and seven patients were infected by the same genotype. DNA extracted from FFPE samples can be used for genotyping; this approach allowed us to demonstrate that multiple P.jirovecii strains were responsible for this cluster, and one genotype was found infecting seven patients. The knowledge of the causative agents of PCP may help to develop new initiatives for control and prevention of PCP among patients undergoing renal transplant and improve routine PCP prophylaxis.