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-15 extended-spectrum β-lactamases (ESBL), and to analyze their distribution in phylo-groups of 150 Escherichia coli isolates from broiler chickens in Ahvaz (Southwest of Iran). Seventy- five cloacal swabs from healthy birds (fecal isolates), and 75 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 41 isolates (54.67%) to A, 9 (12.00%) to B1, 5 (6.67%) to B2, and 20 (26.67%) to D. Of septicemic isolates, 37 isolates (49.33%) were classified as phylotype A, 5 (6.67%) as B1, 10 (13.33%) as B2, and 23 (30.67%) as D. In molecular analysis, a total of 72 isolates (35 fecal and 37 septicemic) were identified to harbor ESBL genes, which were distributed in phylo-groups A, B1, B2, and D. Regardless of the type of isolate, blaCTX-M-15 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.