Pathogenic potential and the role of clones and plasmids in beta-lactamase-producing E. coli from chicken faeces in Vietnam

Background: Antimicrobial resistance (AMR) in food-producing animals is a global public health issue. This study investigated AMR and virulence profiles of E. coli isolated from healthy chickens in Vietnam. E. coli were isolated from fecal samples collected in five chicken farms located in the provinces of Hoa Binh, Thai Nguyen and Bac Giang in the North of Vietnam. These isolates were examined by disk diffusion for their AMR, PCR for virulence and AMR genes, pulsed-field gel electrophoresis for relatedness between bla CMY-2 /bla CTX-M -positive isolates, electroporation for transferability of bla CMY-2 or bla CTX-M genes and sequencing for mutations responsible for ciprofloxacin resistance. Results: Up to 99% of indicator isolates were multidrug resistant. Resistance to third-generation cephalosporins (3GC) was encoded by both bla CTX-M and bla CMY-2 genes; bla CTX-M genes being of genotypes bla CTX-M-1, - 14, - 15, - 17, - 57 and - 87 , whereas ciprofloxacin resistance was due to mutations in the gyrA and parC genes. Some isolates originating from farms located in different provinces of Vietnam were found to be closely related, suggesting they may have been disseminated from a same source of contamination. Plasmids may also have played a role in the diffusion of 3GC-resistance as the bla CMY-2 gene was located on plasmids A/C and I1, and the bla CTX-M gene variants were carried by I1, FIB, R and HI1. Plasmids carrying the bla CMY-2 /bla CTX-M genes also co-transferred resistance to other antimicrobials. In addition, isolates potentially capable of infecting humans, of which some produced bla CMY-2 /bla CTX-M , were identified in this study. Conclusions: Both clones and plasmids could be involved in the dissemination of 3GC-resistant E. coli within and between chicken farms in Vietnam. These results demonstrate the necessity to monitor AMR and control antimicrobial use in poultry in Vietnam.