Analysis of Antibiotic Resistance Profiles of Bacteria Isolated from Catfish Farms and Receiving Water Bodies in Anambra State

The unrestricted use of antibiotics in Nigerian aquaculture has raised concerns about the development and environmental dissemination of antibiotic-resistant bacteria, yet systematic surveillance of resistance profiles in farm-associated bacteria and receiving water environments has not been conducted in Anambra State, South East Nigeria. This study analyses the antibiotic resistance profiles of bacteria isolated from water, fish gut contents, and pond sediments at 20 commercial catfish farms in Awka and Onitsha, and from four receiving water bodies that receive farm effluents. A total of 340 bacterial isolates were obtained and identified to genus level by biochemical testing and 16S rRNA gene sequencing. Antibiotic susceptibility testing was performed using the Kirby-Bauer disc diffusion method against 12 antimicrobial agents representing clinically relevant classes. The prevalence of resistance genes (tetA, tetB, sul1, blaTEM) was determined by PCR. Results showed that 74% of isolates were resistant to at least two antibiotic classes, and 41% were multidrug-resistant, defined as resistance to three or more antibiotic classes. Resistance rates were highest for oxytetracycline (87%), ampicillin (79%), and sulphonamides (68%). Resistance gene prevalence in receiving water body isolates matched farm isolates, confirming environmental dissemination. The study provides the first multidrug resistance surveillance data for aquaculture-associated bacteria in Anambra State and recommends mandatory antibiotic stewardship programmes, prescription-only access to antibiotics for fish farmers, and environmental resistance monitoring as components of a state-level aquatic animal health policy.

Keywords: antibiotic resistance, multidrug resistance, catfish farming, Anambra State, aquaculture bacteria