Unveiling the presence of ESBL-producing coliform bacteria in the aquaculture system of Cumilla District of Bangladesh.

UNLABELLED: The increasing use of antibiotics in aquaculture has raised global concerns about the emergence and spread of antimicrobial resistance (AMR) in aquatic environments.

OBJECTIVES

This study investigated the presence of extended-spectrum β-lactamase (ESBL) producing coliform bacteria and their antibiotic resistance profiles in aquaculture systems across six Upazilas of the Cumilla district of Bangladesh.

METHODS

Water quality parameters (pH, dissolved oxygen, temperature, and ammonia) were measured with HACH kits. Bacterial isolates were screening through culture dependent methods and biochemical tests. Antibiotic susceptibilities were tested by disc diffusion method and resistant genes were identified using qPCR. Isolates ESBL were confirmed by double disc synergy test (DDST).

RESULTS

Microbiological analysis revealed significant variation in the bacterial contamination across sites. The most dominant bacteria were Escherichia coli, Klebsiella spp., Enterobacter spp., and Salmonella spp. All isolates were resistant to multiple antibiotics and multi-drug resistance index (MDRI) values exceeded the threshold 0.2. Isolates showed higher resistance against β-lactam antibiotics. Phenotypic ESBL testing identified 34.3 % of isolates as ESBL producers. The qPCR analysis confirmed the presence of multiple antibiotic resistance genes (ARGs), including bla SHV, bla TEM, bla CMY, bla CTX-M15, Sul1, Sul2, and tetracycline resistance genes, along with mobile genetic elements (MGEs) such as TSO.

CONCLUSION

The findings suggest that aquaculture environments in the Cumilla District may serve as a significant reservoir of multi-drug resistant and ESBL-producing coliform bacteria. Responsible antibiotic practices and regular surveillance are necessary to limit the spread of AMR in the aquaculture industry of Bangladesh.