1.Microbial water quality in pangasius and tilapia aquaculture systems in five regions of Bangladesh
Seikh Razibul Islam ; Md. Emranul Ahsan ; Mohammad Mahfujul Haque ; Muhammad Abdur Razzak ; Louise Schlü ; ter ; Raju Podduturi ; Niels O. G. Jø ; rgensen
Malaysian Journal of Microbiology 2021;17(4):435-451
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