Prevalence of Antimicrobial Resistance in Escherichia coli and Salmonella Species Isolates from Chickens in Live Bird Markets and Boot Swabs from Layer Farms in Timor-Leste

Abstract

The rapid emergence of antimicrobial resistance is a global concern, and high levels of resistance have been detected in chicken populations worldwide. The purpose of this study was to determine the prevalence of antimicrobial resistance in <i>Escherichia coli</i> and <i>Salmonella</i> spp. isolated from healthy chickens in Timor-Leste. Through a cross-sectional study, cloacal swabs and boot swabs were collected from 25 live bird markets and two layer farms respectively. <i>E. coli</i> and <i>Salmonella</i> spp. from these samples were tested for susceptibility to six antimicrobials using a disk diffusion test, and a subset was tested for susceptibility to 27 antimicrobials using broth-based microdilution. <i>E. coli</i> and <i>Salmonella</i> spp. isolates showed the highest resistance towards either tetracycline or ampicillin on the disk diffusion test. <i>E. coli</i> from layer farms (odds ratio:5.2; 95%CI 2.0-13.1) and broilers (odds ratio:18.1; 95%CI 5.3-61.2) were more likely to be multi-drug resistant than those from local chickens. Based on the broth-based microdilution test, resistance to antimicrobials in the Timor-Leste Antimicrobial Guidelines for humans were low, except for resistance to ciprofloxacin in <i>Salmonella</i> spp. (47.1%). Colistin resistance in <i>E. coli</i> was 6.6%. Although this study shows that antimicrobial resistance in chickens was generally low in Timor-Leste, there should be ongoing monitoring in commercial chickens as industry growth might be accompanied with increased antimicrobial use.