Limited Transmission of bla CTX-M-9-Type-Positive Escherichia coli

We examined whether Escherichia coli isolates that produce CTX-M-9-type extended-spectrum -lactamases (ESBL) are trans-ferred between humans and chickens in a Vietnamese community. The phylogenetic group compositions, sequence types, anti-microbial resistance profiles, the prevalence of plasmid antibiotic resistance genes, and the plasmid replicon types generally dif-fered between the human and chicken E. coli isolates. Our results suggest that transmission of the blaCTX-M-9-positive E. coli between humans and poultry was limited. Extended-spectrum--lactamase (ESBL)-producing bacteriahave been rapidly spreading worldwide over the last 30 years (1, 2). ESBL hydrolyzes third-generation cephalosporins and is produced in bacteria, such as Escherichia coli and Klebsiella spp. There are three main groups of ESBL genes: blaTEM, blaSHV, and blaCTX-M. Recently, the CTX-M type of ESBL has become themost prevalent (1). So far, more than 100 genetic variants of blaCTX-M have been confirmed, and the genetic variants were categorized by their amino acids sequence into five main groups: CTX-M-1