Abstract
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.