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

Abstract

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 <em>Escherichia coli</em> 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 <em>colibacillosis</em> (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, <em>bla</em>_CTX-M-15 gene was the most common genotype, followed by <em>bla</em>_TEM and <em>bla</em>_SHV genes. This study suggests that broiler chickens in Iran are infected to ESBL genes- harboring <em>Escherichia coli</em> strains which may be spread to the food chain through fecal contamination of carcasses during slaughtering.