Virulence Gene Constellations Associated with Lethality in Avian Pathogenic E. coli Recovered from Broiler Chickens

In this study, avian pathogenic E. coli (APEC) isolated from broiler chickens in Fayoum and Beni-Suef governorates in Egypt were morphologically and biochemically identified. Selected isolates were serologically identified, and their antimicrobial susceptibility profiles were determined. Ten isolates from the most predominant serogroups were subjected to virulence and antimicrobial resistance genes detection using PCR. In vivo pathogenicity test was performed for 5 E. coli strains that were selected based on serogroups prevalence, virulence, and antimicrobial genes patterns. Results revealed an incidence of 53.8% of E. coli from broiler chickens with the predominance of O125 (30%), O119 (20%), O126, and O86a (15% each) serogroups. The selected 20 E. coli strains were multi-drug resistant (MDR) but sensitive to fosfomycin. The β-lactams and tetracyclines resistance genes were detected in all tested isolates, however, aminoglycoside and quinolone resistance genes were not detected. In this study, 10% of isolates were resistant to colistin and the mcr-1 gene was detected by PCR. In vivo pathogenic strains consistently harbored the virulence gene pattern of fimH, fimA, papC, iutA, and tsh which was the most common gene constellation detected. The detection of tsh gene was consistently associated with lethality in day-old chicks. In conclusion, the current study demonstrated the high prevalence of multidrug-resistant E. coli in broiler chickens representing a potential public health concern. Additionally, the virulence gene constellation of fimH, fimA, papC, iutA, and tsh was found to be associated with lethality in day-old chicks and can be used as a virulence marker of APEC.