Outbreak of Pneumocystis jirovecii Infection Among Heart Transplant Recipients: Molecular Investigation and Management of an Interhuman Transmission

Abstract

Background: An outbreak of Pneumocystis jirovecii pneumonia (PCP) occurred among heart transplant recipients (HTR) at the outpatient clinic of a university hospital, from March to September 2015. Clinical, therapeutic, biological, and molecular data were analyzed to determine its origin and control the outbreak.

Methods: Clinical and biological data regarding all HTR followed in the outpatient clinic were collected. PCP diagnosis was based on microscopy and real-time polymerase chain reaction (PCR). Investigations were performed by building a transmission map, completed by genotyping Pneumocystis isolates and by a control of chemoprophylaxis observance. Asymptomatic exposed patients were screened for colonization using real-time PCR.

Results: Among 124 HTR, 7 PCP cases were confirmed. Screening identified 3 additional patients colonized by P. jirovecii. All patients were cured, and no further cases were identified after trimethoprim-sulfamethoxazole prophylaxis was introduced in the entire cohort. Genotyping demonstrated the same strain in all PCP cases and colonized patients. All cases were linked with possible transmission chains from 2 possible index patients. Interhuman transmission was significantly associated with more frequent visits in the outpatient clinic. Six cases were receiving atovaquone as a prophylaxis. The occurrence of PCP was significantly associated with atovaquone prophylaxis.

Conclusions: This is the first outbreak with detailed molecular analysis in HTR so far. Genotyping and transmission chain confirmed interhuman transmission in all colonized/infected PCP cases. Outpatient clinic layout and high encounters probably caused this PCP cluster, which was controlled after systematic trimethoprim-sulfamethoxazole prophylaxis in exposed patients.