Molecular Evidence of a Nosocomial Pneumocystis jirovecii Transmission among 16 Patients after Kidney Transplantation

Max von Pettenkofer-Institute for Hygiene and Medical Microbiology, University of Munich, Marchioninstrasse 17, 81377 Munich, Germany; Bavarian Health and Food Safety Authority (Bavarian LGL), Veterinaerstrasse 2, 85764 Oberschleissheim, Germany; Department I of Internal Medicine, Nephrology Devision, University Hospital, Munich-Grosshadern, Marchioninistrasse 15, 81377 Munich, Germany; Division of Transplantation Surgery, University Hospital, Munich-Grosshadern, Marchioninistrasse 15, 81377 Munich, Germany

^* To whom correspondence should be addressed. Email: andreas.sing{at}lgl.bayern.de.

	Abstract

In recent years, clusters of Pneumocystis jirovecii (formerly P. carinii) pneumonia (PCP) among immunocompromised individuals were reported. Mostly, the source of infections was suspected within the clinical settings when transplant recipients and PCP patients shared hospital facilities. We report on a cluster of 16 renal transplant recipients positive for P. jirovecii. None of them received anti-Pneumocystis prophylaxis prior to P. jirovecii detection. Epidemiological studies revealed that 15 of them were kidney transplanted at a German university hospital and attended the same inpatient and outpatient clinic from January through September, 2006. Multilocus sequence typing (MLST) was performed on the following genes: ITS1, -tub, 26S and mt26S. P. jirovecii DNA was available from 14 patients and showed identical MLST types among these renal transplant recipients. Surprisingly, one patient who was treated at a different nephrological centre and negated personal contacts to patients from the renal transplantation cluster harbored an identical P. jirovecii MLST type. Three HIV-positive patients and one bone-marrow transplanted hematologic malignancy patient - treated at different medical centres - were used as controls and revealed different MLST types. Interestingly, in three of the four previously described regions new alleles were detected and one new polymorphism was observed in the mt26S region. The epidemiological data and the genotyping results strongly suggest a nosocomial patient-to-patient transmission of P. jirovecii as the predominant transmission route. Therefore, a strict segregation and isolation of P. jirovecii positive/suspected patients in clinical settings seems warranted.