Aims: To determine abundance of potential pathogenic microorganisms in pangasius and tilapia farms in five major fish-producing areas in Bangladesh by PCR approaches. Methodology and results: Important microbial water quality indicators were studied in water of 38 fish farms producing pangasius (Pangasianodon hypophthalmus) and tilapia (Oreochromis niloticus) in five major fish-producing areas of Bangladesh. The parameters included physicochemical data and PCR detection of total coliforms and E. coli, species of potentially pathogenic Vibrio, and cyanobacterial genes encoding the toxins microcystin and saxitoxin. Quantitative PCR showed that coliform bacteria occurred in all fish farms with densities from one to 2.2 × 105 per mL, while E. coli ranged from none to 5.0 × 104 per mL. Numbers of total coliforms and E. coli were higher in pangasius farms than in tilapia farms, and when high abundances occurred, coliform bacteria and E. coli bacteria co-varied. Detection of Vibrio-specific genes indicated presence of Vibrio species in 76% of the farms and included V. vulnificus and V. cholerae. The human pathogen type of V. cholerae (carrying the ctxA gene) and the fish pathogen V. parahaemolyticus were not detected. The microcystin-encoding mcyE gene ranged from undetectable to 2.6 × 105 copies per mL and tended to be highest in pangasius farms. The saxitoxin-encoding gene sxtA was not found in any of the farms. Conclusion, significance and impact of study Based on the high abundance of especially coliform bacteria and E. coli, we recommend more efficient water quality monitoring systems to improve detection and control of fecal coliforms and to reduce presence of microcystin-producing cyanobacteria in aquaculture farms in Bangladesh
Water Quality ; Tilapia ; Catfishes