Microbial Profile and Antimicrobial Resistance in Enteric Pathogens of Farmed Catfish (Pangasianodon hypophthalmus) in Tropical Freshwater Farms

Background: Recently, Pangasianodon hypophthalmus has emerged as an important fish species farmed in India, contributing to food security in the region. Understanding the bacterial flora associated with this fish is essential to ensure food safety, particularly in the Indian context where such studies have been limited. Objective: This study aims to determine the aerobic bacterial flora and antimicrobial resistance in enteric pathogens associated with farmed Pangasianodon hypophthalmus cultured in freshwater ponds in Kerala, India. Methods: The study included enumeration of aerobic plate counts, Pseudomonads, Aeromonas, Enterobacteriaceae and Staphylococcus aureus using standard methods. Bacterial identification was performed using analytical profile index 20E (APE20E) and 16s rDNA sequencing. Antimicrobial resistance was assessed in E. coli, S. aureus and Aeromonas species using disc diffusion assays. Results: The aerobic bacterial flora in catfish muscle tissue included H2S-producing bacteria, Enterobacteriaceae, Pseudomonas, Aeromonas, and B. thermosphacta. Dominant genera identified were Pseudomonas, Burkholderia, Stenotrophomonas, Aeromonas, Klebsiella, and Psychrobacter. Multidrug-resistant strains of enterotoxigenic E. coli and A. hydrophila were recovered, raising concerns about the prevalence of multidrug resistance in A. hydrophila, an etiological agent of red disease in farmed catfish. Conclusion: This study highlights the microbiological risks posed by Aeromonas spp. and enterotoxigenic E. coli in farmed catfish, emphasising their potential as vectors for pathogenic and antibiotic-resistant determinants in the food chain. Recommendations for future research should focus on the development of effective biopreservatives to control these pathogens in processed Pangasius products.