A cluster of Pneumocystis infections among renal transplant recipients: molecular evidence of colonized patients as potential infectious sources of Pneumocystis jirovecii.

BACKGROUND Eighteen renal transplant recipients (RTRs) developed Pneumocystis jirovecii infections at the renal transplantation unit of Brest University Hospital (Brest, Brittany, France) from May 2008 through April 2010, whereas no cases of P. jirovecii infection had been diagnosed in this unit since 2002. This outbreak was investigated by identifying P. jirovecii types and analyzing patient encounters. METHODS The identification of P. jirovecii internal transcribed spacer (ITS) types was performed on P. jirovecii isolates from the 18 RTRs (12 patients with Pneumocystis pneumonia [PCP], 6 colonized patients), 22 unlinked control patients (18 patients with PCP, 4 colonized patients), and 69 patients (34 patients with PCP, 35 colonized patients) with contemporaneously diagnosed P. jirovecii infections in the Brest geographic area. A transmission map was drawn up. Its analysis was combined with the results of P. jirovecii typing. RESULTS P. jirovecii ITS type identification was successful in 14 of 18 RTRs, 15 of 22 control patients, and 48 of the 69 patients. Type Eg was the most frequent type in the 3 patient groups. However, its frequency was significantly higher in the first patient group than in the 2 other groups (P < .05 and P < .01, respectively). Fourteen encounters between RTRs who harbored an identical type were observed. Ten patients were considered as possible index patients, of whom 3 were colonized by the fungus, and 7 presented PCP. CONCLUSIONS The results provide to our knowledge the first data on the role of colonized patients as potential sources of P. jirovecii in a context of nosocomial acquisition of the fungus.