Detection of β-lactam and chloramphenicol resistance genes in Gram-negative bacteria isolated from Clarias gariepinus in selected aquaculture farms

Antibiotic-resistant bacteria (ARB) and their corresponding antibiotic resistance genes (ARGs) are of global public health concern. Documented information on the epidemiology and spread of ARB and ARGs among fish farms in Katsina State, Nigeria is scarce. This study isolated and characterized selected ARB and ARGs from Gram-negative bacteria in fish from aquaculture farms within Katsina State, Nigeria. Hundred apparently healthy C. gariepinus fish samples were randomly collected from five (A, B, C, D) aquaculture farms. Gram-negative bacteria were isolated from samples’ intestines using selective culture media. Isolates were putatively identified using biochemical characterization. Susceptibility of isolates to antimicrobial agents were determined by disk diffusion method while resistance to at least one antibiotic agent in three classes of antibiotics were categorized as Multi-Drug Resistant (MDR). MDR isolates’ identities were further confirmed by Vitek-2 compact system. Beta-lactam and chloramphenicol resistance genes were amplified among all MDR isolates using PCR amplification. Forty-Nine Gram-negative bacteria were isolated. Proteus spp was the most prevalent among samples from farms A (12.24%), D (8.16%) and E (12.24%) while E. coli was highest (8.16%) on farm C. Among the isolates, higher resistance to each of chloramphenicol (48.9%) and cefoxitin (36.7%) compared to gentamicin (2%) and ciprofloxacin (8.2%) was observed. Five (10.20%) MDR isolates were identified while vitek-2 identified Proteus mirabilis (2/5, 40%) and Sphingomonas paucimobilis (2/5, 40%) as the most prevalent MDR bacteria. ARGs detected include: beta-lactam ( bla TEM (4/5), bla SHV (3/5), bla CTX-M (1/5)) and chloramphenicol ( Cat1 (1/5)) resistance genes. Presence of ARGs among Gram-negative bacteria from this study highlights a potential public health concern. Hence, urgent need to monitor and control antibiotics use within aquaculture to mitigate the spread of ARB and ARG to consumers through the food chain is urgently important within the study localities.