Sequence analysis of a CTX-M-1 IncI1 plasmid found in Salmonella 4,5,12:i:-, Escherichia coli and Klebsiella pneumoniae on a UK pig farm

Abstract

Objectives: In 2009, CTX-M Enterobacteriaceae and Salmonella isolates were recovered from a UK pig farm, prompting studies into the dissemination of the resistance and to establish any relationships between the isolates. Methods: PFGEwas used to elucidate clonal relationships between isolates whilst plasmid profiling, restriction analysis, sequencing and PCR were used to characterize the CTX-M-harbouring plasmids. Results: Escherichia coli, Klebsiella pneumoniae and Salmonella 4,5,12:i:- and Bovismorbificans resistant to cefotaxime (n=65) were recovered and 63 were shown by PCR to harbour a group 1 CTX-M gene. The harbouring hosts were diverse, but the group 1 CTX-Mplasmidswere common. Three sequenced CTX-Mplasmids from E.coli, K.pneumoniae and Salmonella enterica serotype 4,5,12:i:-were identical except for sevenmutations and highly similar to IncI1 plasmid ColIb-P9. Two antimicrobial resistance regions were identified: one inserted upstreamof yacABC harbouring ISCR2 transposases, sul2 and floR; and the other inserted within shfB of the pilV shufflon harbouring the ISEcp1 transposase followed by bla CTX-M-1. Conclusions: These data suggest that an ST108 IncI1 plasmid encoding a bla CTX-M-1 gene had disseminated across multiple genera on this farm, an example of horizontal gene transfer of the bla CTX-M-1 gene. © The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.