Impact of antibiotic use on Escherichia coli resistance in goats: A longitudinal cohort study in Selangor, Malaysia

Background and Aim: Antibiotic resistance (ABR) in food animals poses a significant threat to public health under the One Health framework. In Malaysia, Escherichia coli is a key indicator organism for antimicrobial resistance (AMR) surveillance. However, limited data exist on the resistance profiles of E. coli in goats, particularly in relation to antibiotic usage. This study aimed to evaluate the effect of antibiotic use on the temporal development of ABR in E. coli isolated from goat farms in Selangor. Materials and Methods: A prospective cohort study was conducted on two goat farms: one with a documented history of antibiotic use (Farm 2) and one without (Farm 1). A total of 60 goats (30/farm) were followed for 3 months, with fecal samples collected monthly. E. coli isolates were identified and subjected to antimicrobial susceptibility testing using the Kirby–Bauer disk diffusion method. Data were analyzed using Chi-square tests, logistic regression, and Cox proportional hazards modeling. Results: A significant association was found between antibiotic use and the presence of ABR E. coli (odds ratio = 5.82; 95% confidence interval CI: 1.12–30.20; p < 0.05). The highest resistance was observed in Farm 2 (96.74%) compared to Farm 1 (57.14%). A hazard ratio of 1.74 (95% CI: 1.03–2.94) indicated increased risk over time. Resistance was detected against critically important human antibiotics, including ciprofloxacin, ampicillin, chloramphenicol, and tetracycline. Notably, resis­tance to meropenem, an antibiotic not approved for veterinary use, was detected in both farms, suggesting possible envi­ronmental or interspecies transmission. Conclusion: This study confirms that antibiotic use in goat farming significantly influences the development of ABR in E. coli. The detection of resistance in farms without antibiotic use underscores the need to investigate other contributing factors, such as environmental residues and horizontal gene transfer. These findings support policy recommendations to restrict antibiotic use in livestock and highlight the urgency for comprehensive AMR surveillance and intervention strategies. Keywords: antibiotic resistance, antibiotic use, cohort study, Escherichia coli, goats, One Health, Selangor.