Predominance of blaCTX-M-65 and blaCTX-M-55 in extended-spectrum β-lactamase-producing Escherichia coli from raw retail chicken in South Korea.

Abstract

Extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) are a serious public health concern worldwide. The aim of this study was to characterise ESBL-EC isolated from raw retail chicken in South Korea. The antimicrobial resistance, phylogenetic group and virulence gene prevalence of 67 ESBL-EC isolated from retail chicken in South Korea were investigated. All of the isolates possessed blaCTX-M genes, predominantly blaCTX-M-65 (52.2%) and blaCTX-M-55 (25.4%), and three isolates harboured both blaCTX-M-65 and blaCTX-M-55. More than one-half of the ESBL-EC strains also carried blaTEM. Antimicrobial susceptibility testing revealed that 98.5% of the strains were multidrug-resistant (MDR). Phylogenetic analysis showed that group A was predominant (56.7%), followed by B1 (19.4%), E (8.9%), B2 (6.0%) and D (6.0%). Virulence genes associated with extraintestinal pathogenic E. coli (ExPEC) were frequently detected in isolates of phylogenetic groups B1, B2, D and E. The results in this study demonstrate that retail chicken in South Korea is highly contaminated with MDR ESBL-EC and may serve as a reservoir for transmitting ExPEC to humans.