Clinical characteristics of hospital-onset Pneumocystis pneumonia and genotypes of Pneumocystis jirovecii in a single tertiary centre in Korea

BACKGROUND Pneumocystis pneumonia (PCP) may develop as a clinical manifestation of nosocomial pneumonia by means of either reactivation of resident P. jirovecii or de novo infection. However, there have been no studies describing the clinical characteristics of hospital-onset PCP. METHODS A retrospective review of medical records was performed to identify episodes of hospital-onset PCP in a tertiary care centre in Korea between May 2007 and January 2013. We investigated whether human-to-human contact during hospitalisation contributed to PCP development by molecular analysis of the genes encoding mitochondrial large ribosomal subunit (mtLSU) rRNA and dihydropteroate synthase (DHPS) and a review of hospitalisation history. RESULTS During the study period, 129 patients (130 episodes) were diagnosed with PCP. Of these, respiratory specimens from 94 patients during 95 PCP episodes were available for analysis. Sixteen episodes (16.8%) were categorised as hospital-onset PCP. There was a trend toward a higher proportion of haematological malignancy (43.8% [7/16] vs. 20.3% [16/79]; P = 0.058) in patients with hospital-onset PCP compared to patients with community-onset PCP. mtLSU genotype 1 was the most common, occurring in 41 (43.2%) patients. There were four possible cases of nosocomial transmission. Mutation in DHPS was not observed in any PCP episode. CONCLUSIONS PCP can be one of the causes of nosocomial pneumonia, although the mode of acquisition and transmission of P. jirovecii remains uncertain. mtLSU genotype 1 is the predominant P. jirovecii strain in Korea.