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.
Electronic supplementary material
The online version of this article (10.1186/s12917-019-1849-1) co...