A Long-Term Low-Frequency Hospital Outbreak of KPC-Producing Klebsiella pneumoniae Involving Intergenus Plasmid Diffusion and a Persisting Environmental Reservoir

BACKGROUND: To study the molecular characteristics of a long-term, low frequency outbreak of bla (KPC-2) in a low prevalence setting involving the hospital environment. METHODOLOGY/PRINCIPAL FINDINGS: KPC-producing bacteria were screened by selective chromogenic agar and Real-Time PCR. The presence of antibiotic resistance genes was ascribed by PCRs and subsequent sequencing, and the KPC-producing isolates were phylogenetically typed using PFGE and multi-locus sequence typing. Bla (KPC-2)-plasmids were identified and analysed by S1-nuclease-PFGE hybridization and PCR based replicon typing. A ∼97 kb IncFII plasmid was seen to carry bla (KPC-2) in all of the clinical isolates, in one of the isolates recovered from screened patients (1/136), and in the Klebsiella pneumoniae and Enterobacter asburiae isolates recovered from the environment (sinks) in one intensive care unit. The K. pneumoniae strain ST258 was identified in 6 out of 7 patients. An intergenus spread to E. asburiae and an interspecies spread to two different K. pneumoniae clones (ST27 and ST461) of the bla (KPC-2) plasmid was discovered. K. pneumoniae ST258 and genetically related E. asburiae strains were found in isolates of both human and environmental origins. CONCLUSIONS/SIGNIFICANCE: We document a clonal transmission of the K. pneumoniae ST258 strain, and an intergenus plasmid diffusion of the IncFII plasmid carrying bla (KPC-2) in this outbreak. A major reservoir in the patient population could not be unveiled. However, the identification of a persisting environmental reservoir of strains with molecular determinants linked to human isolates, suggests a possible role of the environment in the maintenance of this long-term outbreak.