Characterization of IncF plasmids carrying the blaCTX-M-14 gene in clinical isolates of Escherichia coli from Korea.

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Authors: Juwon Kim ; Il Kwon Bae ; Seok Hoon Jeong ; Chulhun L. Chang ; Chae Hoon Lee ; Kyungwon Lee

Citation: JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY, Vol.66(6) : 1263-1268, 2011

MeSH: Anti-Bacterial Agents/pharmacology ; Bacterial Typing Techniques ; Cefotaxime/pharmacology ; Ceftazidime/pharmacology ; DNA, Bacterial/chemistry ; DNA, Bacterial/genetics ; DNA, Bacterial/metabolism ; Deoxyribonucleases, Type II Site-Specific/metabolism ; Escherichia coli/classification ; Escherichia coli/enzymology* ; Escherichia coli/genetics ; Escherichia coli/isolation & purification* ; Escherichia coli Infections/epidemiology* ; Escherichia coli Infections/microbiology* ; Gene Transfer, Horizontal ; Korea/epidemiology ; Molecular Epidemiology ; Molecular Sequence Data ; Molecular Typing ; Plasmids* ; Polymorphism, Restriction Fragment Length ; Sequence Analysis, DNA ; beta-Lactam Resistance ; beta-Lactamases/genetics*

Abstract: OBJECTIVES: The purpose of this study was to investigate the molecular epidemiology of CTX-M-14-producing Escherichia coli clinical isolates from Korea.

METHODS: A total of 138 non-duplicate E. coli clinical isolates showing reduced susceptibility or resistance to ceftazidime and/or cefotaxime were included in the study. Resistance genes, genetic environment, R plasmid size and replicon type, sequence type (ST) and XbaI-macrorestriction patterns were determined.

RESULTS: Among 138 isolates, 35 were found to carry the bla(CTX-M-14) gene. The ISEcp1 element was identified in the upstream region of the bla(CTX-M-14) gene in 32 isolates. The bla(CTX-M-14) gene was located on an IncF plasmid in 21 isolates, on an IncA/C plasmid in 1 isolate, on the chromosome in 8 isolates and on both the chromosome and an IncF plasmid in 5 isolates. The most prevalent ST was ST405 (n = 8), followed by ST354 (n = 4), ST38 (n = 3), ST69 (n = 3) and the intercontinental ST, ST131 (n = 3). PFGE and multilocus sequence typing experiments demonstrated no major clonal relationship among the CTX-M-14-producing isolates.

CONCLUSIONS: The bla(CTX-M-14) gene was probably mobilized by IncF plasmids, which can readily spread in E. coli, causing horizontal dissemination of the resistance gene in Korea.