Characterization of a CTX-M-15 Producing Klebsiella Pneumoniae Outbreak Strain Assigned to a Novel Sequence Type (1427).

Extended-spectrum -lactamase producing Klebsiella pneumoniae have emerged as one of the major nosocomial pathogens. Between July and September 2012, a CTX-M-15 producing K. pneumoniae caused an outbreak in a university hospital in the Netherlands. The outbreak isolates were characterized and assigned to a novel sequence type (ST1427). An epidemiological link between affected patients was supported by patient contact tracing and whole-genome phylogenetic analysis. Intra-strain polymorphism was detected among multiple isolates obtained from different body sites of the index patient, which may relate to antibiotic treatment and/or host adaptation. Environmental contamination caused by the outbreak clone was found in the patient rooms even on medical equipment. The novel clone was not closely related to any known endemic/epidemic clone, but carried a set of a plasmid-borne resistance genes [bla CTX-M-15, bla TEM-1, bla OXA-1, aac(6')-Ib-cr, qnrB1, tetA(A), aac(3)-II]. Analysis of its virulence factors revealed a previously uncharacterized capsular biosynthesis region and two uncharacterized fimbriae gene clusters, and suggested that the new clone was not hypervirulent. To our knowledge, this is the first outbreak report of K. pneumoniae ST1427, and our study could be of help to understand the features of this newly emerging clone.