Phylogenetic typing and detection of extended-spectrum β-lactamases in Escherichia coli isolates from broiler chickens in Ahvaz, Iran

This study was conducted to reveal the phylogenetic background, to detect the genes encoding TEM, SHV and CTX-M-۱۵ extended-spectrum β-lactamases (ESBL), and to analyze their distribution in phylo-groups of ۱۵۰ Escherichia coli isolates from broiler chickens in Ahvaz (Southwest of Iran). Seventy- five cloacal swabs from healthy birds (fecal isolates), and ۷۵ heart blood samples from birds with colibacillosis (septicemic isolates) were obtained. All isolates were phylotyped and screened for ESBL genes by polymerase chain reaction (PCR). The fecal isolates belonged to four main phylo-groups, including ۴۱ isolates (۵۴.۶۷%) to A, ۹ (۱۲.۰۰%) to B۱, ۵ (۶.۶۷%) to B۲, and ۲۰ (۲۶.۶۷%) to D. Of septicemic isolates, ۳۷ isolates (۴۹.۳۳%) were classified as phylotype A, ۵ (۶.۶۷%) as B۱, ۱۰ (۱۳.۳۳%) as B۲, and ۲۳ (۳۰.۶۷%) as D. In molecular analysis, a total of ۷۲ isolates (۳۵ fecal and ۳۷ septicemic) were identified to harbor ESBL genes, which were distributed in phylo-groups A, B۱, B۲, and D. Regardless of the type of isolate, blaCTX-M-۱۵ gene was the most common genotype, followed by blaTEM and blaSHV genes. This study suggests that broiler chickens in Iran are infected to ESBL genes- harboring Escherichia coli strains which may be spread to the food chain through fecal contamination of carcasses during slaughtering.

Keywords:

beta-Lactamase , Chicken , <i>Escherichia coli</i> , phylogeny