Antimicrobial resistance pattern in farm-raised tilapia: A study in north Sarawak, Malaysia

Aims:The rapid expansion of tilapia aquaculture in Northern Sarawak has raised concerns regarding antibiotic use and the emergence of antimicrobial resistance (AMR).This study investigated the prevalence, antimicrobial susceptibility profiles, and multidrug resistance (MDR) patterns of Escherichia coli and Salmonella spp.isolated from farmed tilapia in Bintulu and Miri, Sarawak.Methodology and results: A total of 126 samples from 42 tilapia were analysed using culture-based methods, biochemical identification, 16S rRNA sequencing, and antimicrobial susceptibility testing via the Kirby-Bauer disc diffusion method.Escherichia coli was detected in all samples (100%), while Salmonella spp. was identified in 47.6% samples.High resistance levels in E. coli were observed for ampicillin (64.5-74.5%),cefotaxime (62-64%), and streptomycin (63.5-77.5%).Similarly, Salmonella spp.exhibited substantial resistance to ampicillin (up to 95%), cefotaxime (75-80%), and trimethoprim-sulfamethoxazole (61.5-78.5%).Significant differences in resistance profiles were observed between sampling locations (p < 0.05).MDR, defined as resistance to at least three antimicrobial classes, was detected in 59.7-63.4% of isolates, with higher prevalence in Salmonella spp.(56.7-73.3%)than E. coli (54.0-65.1%). Conclusion, significance and impact of study:The findings demonstrate a substantial AMR burden in aquaculture systems, highlighting tilapia as a potential reservoir of antimicrobial-resistant bacteria.Strengthened surveillance, antimicrobial stewardship, and sustainable aquaculture practices are essential to mitigate resistance risks to public health and the environment.