Antibiotic Resistance and Molecular Epidemiology of ESBL-Producing E. coli in Shrimp Aquaculture: A Study from Tiruvallur District, Tamil Nadu, India.

The rapid growth of aquaculture and rising demand for high-quality animal protein have resulted in increased usage of antimicrobials in fish farming, raising worries about the rise of antibiotic resistance. This study was carried out to determine the prevalence of ESBL-producing E. coli in shrimp farms of Tiruvallur district, Tamil Nadu, South India for a duration of 5 months from February 2022 to June 2022. A total of 102 samples from 22 shrimp farms were collected, including 51 shrimp, 10 soil, 37 water, and 4 feed, with 73 of 79 E. coli isolates (92.4%) producing ESBL. Three E. coli isolates positive for the stx2 gene were discovered in shrimp farms with high and medium salinity. Antibiotic resistance patterns found that chloramphenicol had the lowest rate of resistance (2.5%), while ampicillin had the highest rate of resistance (39.2%). Approximately 70% of the isolates were multidrug resistant. Molecular screening revealed that the blaTEM gene is the most prevalent beta-lactamase gene (39.4%), followed by blaCTX (27.3%), blaSHV (24.3%), and ampC (19.2%). Additionally, the sul1 gene was found in 8.1% of isolates. These findings suggest that the prevalence of E. coli with virulent characteristics and high level of contamination in fisheries pose a public health danger, potentially affecting consumer health as well as prawn export markets. The finding of multidrug-resistant E. coli in shrimp aquaculture emphasizes the importance of increased biosecurity and antibiotic stewardship in preventing contamination and protecting public health.