Narayanan et al. V. parahaemolyticus With Pathogenic Potential in Seafood The conventional methods used to identify the pathogenic V. parahaemolyticus would be good for clinical isolates, but a more elaborate method is recommended for the detection of tdh gene in environmental isolates. This is the first comprehensive study on pathogenic V. parahaemolyticus in Kerala, India and demonstrates for the first time, the isolation of potentially pathogenic V. parahaemolyticus, carrying tdh gene from seafood collected from retail markets in Kerala.

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Isolation and characterization of Halothiobacillus sp. from the shrimp aquaculture farm soil and their sulphur oxidation ability and utilization of H S in in-vitro model. 2 Starkeys mineral salt medium was used to screen autotrophic sulphur oxidizing bacteria. For the qualitative screening, bacterial isolates were inoculated in mineral salt medium containing bromo phenol blue indicator to monitor change in pH. The isolates were studied further for their sulphate ion production, sulphur oxidase enzyme production and utilization of Na S. Identification was carried out by 2 conventional biochemical and molecular methods. Fifty isolates showed distinct sulphur oxidizing ability on the mineral salt medium. The pH reduction test revealed that out of fifty isolates six could efficiently reduce the pH of the medium to 3.0 from an o-1 initial pH of 7 within 96 hr of incubation at 30 C. Maximum sulphate ion (12.65 mg ml) and sulphur oxidase-1-1 enzyme (16.64 mM sulphate hr ml) was produced by a bacterial isolate, Halothiobacillus sp. strain rk3. All the six isolates efficiently utilized Na S in in-vitro conditions. Conventional and molecular identification (16S 2 rRNA sequence analysis) revealed that the sulphur oxidizing bacterial isolates belonged to Halothiobacillus spp. Furthermore, sequencing similarity calculation showed an average nucleotide identity (ANI) values higher than 99% which suggests that the isolates were not genetically different. The present investigation revealed the presence of Halothiobacillus sp. as natural microflora of farm soils in shrimp aquaculture.

The effect of dietary supplementation of probiotic bacterium Bacillus licheniformis on the histopathological changes in Macrobrachium rosenbergii juveniles (4.0 AE 0.02 g) challenged with known pathogenic strain of Vibrio alginolyticus are reported. Two isocaloric basal diets supplemented with probiotic bacteria B. licheniformis (1.0 9 10 9 cfu/g feed) and other without probiotic supplementation were fed to the M. rosenbergii juveniles for 45 days. The histological observations revealed no significant changes in the hepatopancreas and gut tissues of both the experimental and the control groups which indicate that the present bacterium is a safe candidate probiont for the host. Prawns were challenged with V. alginolyticus after 45 days of feeding with probiotic diet. The histopathological studies of the hepatopancreas revealed that M. rosenbergii fed with probiotic-supplemented diet showed less changes as compared to the prawns fed with control diet on second and fourth day of post-experimental challenge with V. alginolyticus. Histopathological observations revealed that the gills of the prawns fed with control diet were severely affected in comparison to the prawns fed with probiotic-supplemented diet after challenging with V. alginolyticus. Results from this study revealed the improved protection by dietary incorporation of B. licheniformis in reducing the histopathological manifestations due to V. alginolyticus infection in freshwater prawn. K E Y W O R D S Bacillus licheniformis, histopathology, Macrobrachium rosenbergii, probiotic