Population structure of OXA-48-producing Klebsiella pneumoniae ST405 isolates during a hospital outbreak characterised by genomic typing.

OBJECTIVES: The aim of this study was to investigate the structure of a broad and sustained hospital outbreak of OXA-48-producing Klebsiella pneumoniae (KpO48) belonging to sequence type 405 (ST405).

METHODS: Whole-genome sequencing and comparison of ten ST405 KpO48 isolates obtained from clinical samples in our hospital was performed. Using stringent criteria, 36 single nucleotide polymorphisms (SNPs) were detected (range 0-21 in pairwise comparisons), and allele-specific PCR was used to call the SNPs among a larger set of isolates.

RESULTS: Several haplotypes were identified within the population. The haplotypes did not show a spatial structure, but a temporal evolution of sequential haplotype replacements was observed.

CONCLUSIONS: The dispersed spatial distribution suggests a reservoir formed by a large pool of colonised patients, and the temporal replacement pattern suggests that the sustained outbreak was composed of several small outbreaks that appeared and rapidly dispersed to several units.