Molecular variations in Vibrio alginolyticus and V. harveyi in shrimp-farming systems upon stress

A study was performed to investigate the genomic variations in the shrimp farm isolates of Vibrio alginolyticus and V. harveyi when the isolates were subjected to environmental stress. Samples of shrimps, water and sediment were collected from Southern Indian coastal shrimp farms. Vibrio isolates were biochemically identified and confirmed using 16S rDNA and gyrB gene specific PCR. The bacterial strains were genotyped by PCR fingerprinting using GTG(5) and IS (Insertion Sequence) primers. Seven strains each of V. alginolyticus and V. harveyi were subjected to 10 passages through trypticase soya broth (TSB), which contained different NaCl concentrations (3, 6 and 8%) and trypticase soya agar (TSA). V. alginolyticus was also passaged through TSB with a 12% NaCl concentration. PCR fingerprinting, which was performed on the strains that were passaged through different salt concentrations, confirmed that V. alginolyticus and V. harveyi could affect the genomic variations, depending on the environmental conditions of the culture. The study highlights the complex genotypic variations that occur in Vibrio strains of tropical aquatic environment because of varied environmental conditions, which result in genetic divergence and/or probable convergence. Such genetic divergence and/or convergence can lead to the organismal adaptive variation, which results in their ability to cause a productive infection in aquatic organisms or generation of new strains.

New host record of five Flavobacterium species associated with tropical fresh water farmed fishes from North India

Abstract Yellow pigmented, filamentous, Gram-negative bacteria belonging to genus Flavobacterium are commonly associated with infections in stressed fish. In this study, inter-species diversity of Flavobacterium was studied in apparently healthy freshwater farmed fishes. For this, ninety one yellow pigmented bacteria were isolated from skin and gill samples (n = 38) of three farmed fish species i.e. Labeo rohita, Catla catla and Cyprinus carpio. Among them, only twelve bacterial isolates (13.18%) were identified as Flavobacterium spp. on the basis of morphological, biochemical tests, partial 16S rDNA gene sequencing and phylogenetic analysis. On the basis of 16S rDNA gene sequencing, all the 12 isolates were 97.6-100% similar to six different formally described species of genus Flavobacterium. The 16S rDNA based phylogenetic analysis grouped these strains into six different clades. Of the 12 isolates, six strains (Fl9S1-6) grouped with F. suncheonense, two strains (Fl6I2, Fl6I3) with F. indicum and the rest four strains (Fl1A1, Fl2G1, Fl3H1 and Fl10T1) clustered with F. aquaticum, F. granuli, F. hercynium and F. terrae, respectively. None of these species except, F. hercynium were previously reported from fish. All the isolated Flavobacterium species possessed the ability of adhesion and biofilm formation to colonize the external surface of healthy fish. The present study is the first record of tropical freshwater farmed fishes as hosts to five environmentally associated species of the Flavobacterium.

Microbial control of the invasive spiraling whitefly on cassava with entomopathogenic fungi

Abstract The entomopathogenic fungi Beauveria bassiana, Metarhizium anisopliae, Lecanicillium lecanii and Isaria fumosorosea were tested for their efficacy in managing the exotic spiraling whitefly Aleurodicus dispersus (Hemiptera, Aleyrodidae) on cassava (Manihot esculenta) during 2 seasons (2011-2012 and 2012-2013). The fungi I. fumosorosea and L. lecanii exhibited promising levels of control (> 70% mortality of the A. dispersus population). The percent mortality increased over time in both seasons. Application of I. fumosorosea was highly pathogenic to A. dispersus in both seasons compared to the other entomopathogenic fungi. Analysis of the percent mortality in both seasons revealed differences in efficacy between 3 and 15 days after treatment. The season also influenced the effects of the fungi on the A. dispersus population. Thus, entomopathogenic fungi have the potential to manage A. dispersus infestation of cassava.

Yersinia enterocolitica in slaughtered food animals

500 samples were collected from 100 freshly slaughtered food animals, 25 of each of beef, veal, mutton, and goat carcasses. Each carcass was represented by part of diaphragmatic muscle, liver and mesenteric lymph nodes. Moreover, rectal swab and surface swab from the thigh extended to outside of abdomen, chest and shoulder were collected. The samples were cold enriched and then inoculated on Yersinia selective agar base with supplement. Yersinia enterocolitica was more frequently isolated from livers [9%] than mesenteric lymph nodes and rectal swabs, each constituting 5%, then the surface swabs [2%] and finally the muscle [1%]. The incidence of Y. enterocolitica amongst beef samples [7.2%] was higher than in samples collected from mutton, goat and veal, each constituting 3.2%, 5.6% and 1.6%, respectively. The public health significance of Y. enterocolitica as a food borne disease was discussed

Occurrence and public health importance of some microorganisms in edible offals

100 samples of raw edible offals [25 samples each of heart, liver, rumen and intestine] were examined for enumeration of Enterobacteriaceae, Staphylococcus aureus, Enterococci and also for isolation and identification of Enterobacteriaceae organisms. Examination of the samples revealed that the average count of Enterobacteriaceae and Staph. aureus was 2 x 10[4] and 5 x 10[2], 4 x 10[4] and 4 x 10[3], 7 x 10[5] and 2 x 10[4], and 2 x 10[6] and 4 x 10[4] per gram samples of heart, liver, rumen and intestine, respectively, while the average count of Streptococcus faecalis per gram of the same examined samples was 2 x 10[3], 9 x 10[3], 2 x 10[4] and 6 x 10[4], respectively. The public health importance of isolated microorganisms as well as the suggested hygienic measures to improve the quality of raw edible offals were discussed