Detection of avian pathogenic Escherichia coli (APEC) and antimicrobial resistance in layer parent stock in Bangladesh: Insights into phenotypic and genotypic profiles.

Avian pathogenic Escherichia coli (APEC) poses a major threat to poultry health and productivity, particularly in layer parent stock, resulting in substantial economic losses. This study aimed to determine the occurrence of APEC along with their virulence and resistance profile in the layer parent stock. A total of 89 samples, including cloacal swabs from 36 live birds and liver swabs from 53 dead birds, were collected. E. coli was isolated using culture, biochemical, and PCR methods. APEC-related virulence genes were detected via PCR, while antimicrobial susceptibility was evaluated using the disc diffusion method and PCR. The overall prevalence of E. coli was 82 %, with similar detection rates in live (83.3 %) and dead birds (81.1 %). In PCR, APEC-associated gene fimC was detected in 95.9 % of the isolates, papC in 36.9 %, and iucD in 15.1 %, with no significant difference between those from live and dead birds. All isolates were multidrug-resistant, where all E. coli isolates from both live and dead birds were resistant to ampicillin (100 %), with high resistance to cefotaxime (live: 100 % vs. dead: 93 %), tetracycline (80 % vs. 88.4 %), nalidixic acid (100 % vs. 62.8 %), streptomycin (66 % vs. 39.5 %), norfloxacin (40 % vs. 20.9 %), and chloramphenicol (20 % vs. 25.6 %). Moreover, genes conferring resistance to tetracyclines [tetA (live: 10/10 vs. dead: 10/10) and tetB (1/10 vs. 10/10)] and beta-lactams [blaTEM (10/10 vs. 10/10), blaCTX-M (1/10 vs. 4/10), and blaSHV (2/10 vs. 0/10)] were detected in isolated E. coli. The results recommend periodic surveillance and policy interventions to mitigate health risks and economic losses.