Extended-spectrum beta-lactamase (ESBL) production and virulence genes profile of avian pathogenic Escherichia coli (APEC) isolated from broiler chickens in eastern Thailand

Avian pathogenic Escherichia coli (APEC) causes colibacillosis, resulting in extensive economic losses for the broiler industry. To date, there is little information in Thailand about virulence-associated genes and antibiotic resistance of APEC strains. Here, this study aimed to investigate the virulence genes and extended-spectrum beta-lactamase (ESBL) characteristics of APEC isolated from broilers. This study used multiplex polymerase chain reaction (PCR) to determine the presence of virulence genes and resistance genes in APEC. Furthermore, the disc diffusion method examined ESBL phenotypes of APEC and antibiotic resistance profiles against 17 antimicrobials. In this study, E. coli was isolated 11 (6.32%) of 174 broiler visceral organs. All E. coli isolates were tested for five APEC-virulence-associated genes (iroN, ompT, hlyF, iutA, and iss). Eight E. coli isolates from broilers with colibacillosis-associated lesions carried two (iroN and ompT) of the APEC virulence genes. One APEC virulence gene (hlyF) was found in E. coli isolates from broilers without lesions. Possibly no individual virulence gene was specific to the APEC strain. Interestingly, the papC, previously detected in humans with uropathogenic E. coli, was found in an APEC isolate. All APEC isolates were ESBL-producing E. coli, and then they were tested for four beta-lactamase-encoding genes (blaTEM, blaCTX-M, blaOXA, and blaSHV). The blaTEM and blaCTX-M were identified in 81.81% (9/11) of the isolates, whereas blaOXA or blaSHV were not detected in any isolate. All APEC showed multi-drug resistance (MDR) phenotypes, especially chloramphenicol, erythromycin, and sulfamethoxazole-trimethoprim. Although antibiotics were not recently used, MDR might be encouraged by horizontally transferring antibiotic-resistance genes. In addition, fluoroquinolone resistances were found in APEC isolates which could transfer resistance genes to humans via the food chain. This study indicates that APEC isolates contain several virulence and bla genes and should be surveillance to prevent the transmission of those genes to humans.