Search

Shrimp aquaculture industry comprises 15 % of the internationally traded seafood products targeted for human consumption. Diseases of shrimp have caused severe economic losses to the aquaculture industry. Among pathogenic bacteria, several Vibrio species known as shrimp pathogens are also human pathogens. This study was conducted to identify the incidence of diversified Vibrio species in the shrimp Penaeus monodon Fabricius, 1798 farms in Bangladesh. Different Vibrio selective media were used for primary isolation and 16S rRNA gene amplicons were sequenced, followed by phylogenetic analysis. The Vibrio strains were also tested against twelve antibiotics. Two strains V32 and V38 showed 99.93 % similarity with Vibrio azureus whereas V9 and V33 showed 100 % identity with Vibrio fluvialis. Comparison of 16S rRNA gene sequence of V37 with sequences from GenBank identified the strain as Vibrio xuii. The phylogenetic tree indicates that V24, V26, V34 and V35 are closely related with Vibrio parahaemolyticus. The strains V28 and V31 were identified as Vibrio vulnificus. One strain of Vibrio cholerae was also identified. Moreover, V22 was identified as Photobacterium damselae subsp. damselae, and V25 as Aeromonas hydrophila. Twelve strains of Vibrio were resistant to amoxycillin, whereas all 16 bacterial isolates showed sensitivity to nitrofurantoin, sulphamethoxazole, chloramphenicol, ciprofloxacin and tetracycline. Multidrug resistance was observed in three isolates viz. V28, V32 and V35 which were identified as V. vulnificus, V. azureus and V. parahaemolyticus, respectively having MAR index of 0.25. These findings might have potential applications in controlling shrimp and human pathogenic vibrios in the farming regions. [ABSTRACT FROM AUTHOR]

The use of chemotherapeutic agents has been questioned for disease management in shrimp aquaculture due to the emergence of drug-resistant bacteria and enduring residual effects in the environments. Instead, microbial interventions in sustainable aquaculture have been proposed, and among them, the use of probiotics as an alternative to antibiotics has gained considerable attention. Earlier, we short-listed nineteen isolates out of ninety six bacteria, isolated from shrimp ghers of coastal areas of Bangladesh that exhibited antagonistic potential against pathogenic vibrios, and non-hemolytic property, presumably indicating their harmless behavior in mammalian system at least in vitro. This prompted us to study their cytotoxic effect in vivo using brine shrimp Artemia franciscana. Six isolates were found having higher lethal values compared with others. Four of them, identified as Pseudomonas and Bacillus spp. exhibited the lowest inhibition against Artemia and were considered safe. Further, in a co-culture experiment it was evident that the isolated probiotic bacteria were shown to outcompete the growth of pathogenic Vibrio harveyi due to their antagonistic properties. The probionts can now therefore be tested in culture environment of Bangladesh in order to understand the effectiveness of microbial control of bacterial diseases in shrimp aquaculture. [ABSTRACT FROM AUTHOR]