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In October 2012, an outbreak of gentamicin-resistant, ciprofloxacin non-susceptible extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae occurred in a neonatal intensive care unit in Ireland. In order to determine whether the outbreak strain was more widely dispersed in the country, 137 isolates of K. pneumoniae with this resistance phenotype collected from 17 hospitals throughout Ireland between January 2011 and July 2013 were examined. ESBL production was confirmed phenotypically and all isolates were screened for susceptibility to 19 antimicrobial agents and for the presence of genes encoding bla TEM, bla SHV, bla OXA, and bla CTX-M; 22 isolates were also screened for bla KPC, bla NDM, bla VIM, bla IMP and bla OXA-48 genes. All isolates harboured bla SHV and bla CTX-M and were resistant to ciprofloxacin, gentamicin, nalidixic acid, amoxicillin-clavulanate, and cefpodoxime; 15 were resistant to ertapenem, seven to meropenem and five isolates were confirmed as carbapenemase producers. Pulsed-field gel electrophoresis of all isolates identified 16 major clusters, with two clusters comprising 61% of the entire collection. Multilocus sequence typing of a subset of these isolates identified a novel type, ST1236, a single locus variant of ST48. Data suggest that two major clonal groups, ST1236/ST48 (CG43) and ST15/ST14 (CG15) have been circulating in Ireland since at least January 2011.

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