Total-Bacterial-Load-and-Enumeration-of-Pathogenic-Bacteria-vibrio-spp.-Aeromonas-spp-and-Pseudomonas-spp-in-the-Production-Line-of-Mud-Crab-Scylla-olivacea-Hatchery-in-Bangladesh
Total-Bacterial-Load-and-Enumeration-of-Pathogenic-Bacteria-vibrio-spp.-Aeromonas-spp-and-Pseudomonas-spp-in-the-Production-Line-of-Mud-Crab-Scylla-olivacea-Hatchery-in-Bangladesh
Md. Rashedul Islam1, Abul Farah Md. Hasanuzzaman1*, Md. Latiful Islam2, Ghausiatur Reza Banu1
ABSTRACT
The increasing demand for mud crabs (Scylla spp.) has created immense pressure on the wild populations globally. To reduce threats to wild stocks, it has become an urgent issue of increasing mud crab larvae production in captivity. But some chitinolytic bacteria (Vibrio spp., Aeromonas spp., and Pseudomonas spp.) poses major threats in the production line of mud crab larvae. Hence, the present study tried to determine prevalence and load of total and pathogenic bacteria in the different components of the mud crab hatchery. Selective agar media, a series of biochemical tests, and bacteria isolation kits were used for the isolation and identification of bacteria. The genus Vibrio, Aeromonas and Pseudomonas were identified in different components of the larval production line in the hatchery. V. mimicus, V. parahaemolyticus, V. harveyi and V. alginolyticus were the major species identified from the Vibrio genus. The average concentrations of Vibrio spp. in brood, brood’s tank water, eggs, larvae, larval tank water, and larval feed were log10 3.86±0.61 cfu g-1, log10 3.63±0.57 cfu mL-1, log10 2.73±0.13 cfu g-1, log10 2.86±0.21 cfu g-1, log10 2.93±0.25 cfu mL-1 and log10 3.23±0.37 cfu mL-1 respectively. The highest concentration of Aeromonas spp. (log10 3.62±0.24 cfu g-1) and Pseudomonas spp. (log10 2.95±0.22 cfu g-1) was detected in the brood sample of batch 1 and batch 4, respectively. The variations in Aeromonas and Pseudomonas counts among different batches of different components were statistically non-significant (p>0.05). While, most of the components along the larval production line had significantly (p<0.05) varied Vibrio counts for different batches. Larval feeds were found mostly contaminated with pathogenic bacteria, especially with pathogenic Vibrio in the production line of the hatchery; hence, special biosecurity measures are needed in this particular component to substantially reduce horizontal transmission of such pathogens in the larvae; particularly axenic live food culture is to be practiced. The knowledge gained from this study will be useful to the hatchery operators taking appropriate measures to strengthen the biosecurity line for controlling bacterial contamination of the various biological and physical components, and thus for reducing larval mortality within an acceptable range in captivity.
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