Epidemiological Outbreaks of Pneumocystis jirovecii Pneumonia Are Not Limited to Kidney Transplant Recipients: Genotyping Confirms Common Source of Transmission in a Liver Transplantation Unit

Over a 5-month period, four liver transplant patients at a single hospital were diagnosed withPneumocystis jiroveciipneumonia (PCP). This unusually high incidence was investigated using molecular genotyping. Bronchoalveolar lavage fluids (BALF) obtained from the four liver recipients diagnosed with PCP were processed for multilocus sequence typing (MLST) at three loci (SOD, mt26s, andCYB). Twenty-four other BALF samples, which were positive forP. jiroveciiand collected from 24 epidemiologically unrelated patients with clinical signs of PCP, were studied in parallel by use of the same method.Pneumocystis jiroveciiisolates from the four liver recipients all had the same genotype, which was different from those of the isolates from all the epidemiologically unrelated individuals studied. These findings supported the hypothesis of a common source of contamination or even cross-transmission of a singleP. jiroveciiclone between the four liver recipients. Hospitalization mapping showed several possible encounters between these four patients, including outpatient consultations on one particular date when they all possibly met. This study demonstrates the value of molecular genotyping ofP. jiroveciiisolated from clinical samples for epidemiological investigation of PCP outbreaks. It is also the first description of a common source of exposure to a singleP. jiroveciiclone between liver transplant recipients and highlights the importance of prophylaxis in such a population.