Antimicrobial drug resistance at the human-animal interface in Vietnam

This thesis investigates the prevalence of antimicrobial resistance (AMR) among non-typhoidal Salmonella (NTS) and E. coli strains isolated from backyard farm chickens and humans in Vietnam. We found that this prevalence was to some extent related to antimicrobial usage. In particular, extended-spectrum beta-lactamases (ESBL) E. coli colonization in humans was associated with human use of antimicrobials. Whereas in chickens, fluoroquinolones use was associated with ciprofloxacin resistant E. coli and colistin use was associated with the presence of bacteria carrying the colistin resistance encoding mcr-1 gene. Moreover, the host specificity of Enteroaggregative Escherichia coli (EAEC) was observed in our study since these strains were only detected from human samples. We have also compared the risk of human colonization with antimicrobial resistant bacteria or resistance determinants as a result of chicken farming in southern Vietnam. We demonstrated that although having direct contact with chickens, farmers are not more likely to become a carrier of NTS than individuals who are not exposed to chicken on a daily basis. In addition, the prevalence of ESBL E. coli colonization and ESBL genes are distinguishable between chickens and humans. However, farmers working with mcr-1 positive chickens are more likely to carry mcr-1 positive bacteria. Our study indicates that although bacterial transfer maybe limited between humans and chickens, transmission of AMR determinants is extremely complex and likely to occur in multiple directions.