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Theses (PG)

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2020 - 20213
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Subject: Fisheries × End date: 2021 × Start date: 2020 ×
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    ThesisItemOpen Access
    SCREENING OF BACTERIAL PATHOGENS ASSOCIATED WITH DISEASED FRESHWATER ORNAMENTAL FISHES
    (KARNATAKA VETERINARY, ANIMAL & FISHERIES SCIENCES UNIVERSITY, BIDAR, 2021) AMIT KUMAR SOREN,; S.K.GIRISHA
    Bacterial diseases are the major constraints in each and every fish culture system of ornamental fishery sector. Bacteria are considered as ubiquitous and are always in contact with the fish. Hence the risk of catching a disease is high when the fish falls under stressful conditions. Screening for major pathogenic bacteria associated with ornamental fish diseases will aid in knowing the probable reason for the untimely death in many ornamental cultures and rearing systems. In the present study, 50 isolates of bacteria were screened from 30 freshwater ornamental fish samples. The fishes exhibited clinical signs like exophthalmia, dropsy, erratic movement, dermal ulceration, haemorrhages, etc. The isolates were subjected to series of biochemical tests and polymerase chain reaction (PCR) assay for identifying their respective genus/species. The tests revealed that the isolates were dominated by the Gram-negative bacteria with Aeromonas spp., followed by Citrobacter spp. and Pleiosomonas spp. Virulence factors like haemolysis, gelatinase and starch hydrolysis were performed. Haemolytic assay revealed that 48% of the isolates were α-haemolytic and 26% were β-haemolytic. Amylase and gelatinase activity was present in 46% and 50% of the isolates respectively. Further, selected 4 isolates (positive for all the virulence factors) were used for 16S rRNA sequencing. The obtained sequences indicated the 4 selected isolates as Aeromonas hydrophila (F3), A. veronii (D2), A. sobria (F7) and Citrobacter freundii (G9-1A); two of them were deposited in GenBank [MN594480.1 (A. hydrophila F3) and MN593732.1 (A. veronii D2)]. The phylogenetic tree analysis found that A. hydrophila, A. sobria, A. veronii. and C. freundii were closely related to reference strain of A. hydrophila (FN997612.1), A.sobria (KM516017.1), A.veronii (EU770280.1) and C. freundii EnZ-4 (MN220573.1) respectively. The antibiotic susceptibility test of the 4 isolates reveal
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    ThesisItemOpen Access
    EVALUATION OF OUTER MEMBRANE PROTEIN K (OMPK) IN PROTECTING LITOPENAEUS VANNAMEI AGAINST VIBRIO HARVEYI INFECTION
    (KARNATAKA VETERINARY, ANIMAL AND FISHERIES SCIENCES UNIVERSITY, BIDAR, 2020) SAPTAMI. R. JOGALEKAR; M.N.VENUGOPAL
    Outer membrane proteins (OMPs) are present in many prokaryotes and in some organelles of eukaryotic cells. In Gram-negative bacteria, they are considered as the important molecules as they play various roles in bacterial adaptation including pathogenicity of bacterium. As OMPs are present on the outer surface of the bacterial cell and are the first line of contact between the bacterium and its surroundings, they are considered as good vaccine candidates. Studies have showed that vaccines consisting of immunogenic fractions can induce higher protection than inactivated whole-cell bacteria in fish and other vertebrates. Research has shown OMPs extracted from several bacterial fish pathogens viz., Edwardsiella ictaluri, E. tarda, Vibrio vulnificus, Aeromonas salmonicida, and A. hydrophila to be protective antigens in fish. As no study is currently available for the evaluation of the effect of OmpK on shrimp, present work aims to study the immunogenic potential of OmpK, and its suitability as a protective candidate against Vibrio harveyi infection in the shrimp, Litopenaeus vannamei. In the present study, preliminary investigation has been undertaken into existing OmpK sequences in GenBank database engaging bioinformatics tools to understand the suitability of OmpK as a vaccine candidate. Primers were designed for the amplification of OmpK gene of V. harveyi, and the gene was later cloned and expressed using E. coli SG cells. Further, the protein was purified through Ni-NTA affinity chromatography after successful confirmation by SDS-PAGE, and its effectiveness against V. harveyi was evaluated which showed RPS 75 respectively. Our results suggest that OmpK of V. harveyi could be used as a potential protective candidate for L. vannamei against V. harveyi infection.
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    ThesisItemOpen Access
    ISOLATION AND CHARACTERIZATION OF VIBRIO MIMICUS AND VIBRIO (GRIMONTIA) HOLLISAE FROM SEAFOOD
    (KARNATAKA VETERINARY, ANIMAL AND FISHERIES SCIENCES UNIVERSITY, BIDAR, 2020) PAVANA, V.,; M.N.VENUGOPAL
    healthy diet. Major health risks are involved in the consumption of raw or undercooked seafood that may be naturally contaminatedby foodborne pathogens present in the marine environment. Group of Vibrios are associated with live seafood, asthey are the indigenous microflora of the marine environment. Seafood contaminated withpathogenic Vibrios not only play an important role in the transmission of diseases but also act as areservoir in the marine realms. As the foodborne infections of Vibrio spp. are common in seafood, it is necessary to survey thepresence of toxigenic and non-toxigenic Vibrios from various seafood and their environment. In the present study, 50 different seafood samples were collected from Mangaluru (Dakshina Kannada District), Mulki, Udupi and Kundapura (Udupi District), Bhatkal, Ankola, and Karwar (Uttara Kannada District). A total of 365 isolates were suspected as Vibrios from the collected samples that were plated on different isolation media. Out of 365 suspected isolates, 3 isolates of V. mimicus and 1 isolate of V. hollisae were confirmed phenotypically by performing battery of biochemical tests. These isolates were further confirmed by performing Polymearse Chain Reaction (PCR) using specific primers, in which AraC gene was targeted to V. mimicus (488 bp) and gyrB gene to V. hollisae (363 bp).Phenotypically confirmed V. mimicus showed negative result as they failed to amplify at specific basepair and V. hollisae showed positive result by amplifying at its specific base pair. For further confirmation, 16S rRNA sequence analysis was done by out sourcing for the genotypically confirmed V .hollisae. The BLAST sequence analysis, revealed that V.hollisae strain matches with 91 V. alginolyticus, but 16S rRNA is closely related to Grimontia hollisae sequences present in NCBI gene database. Haemolyitc assay was also performed for the phenotypically confirmed V. mimicus and V. hollisae to test their virulence.V. mimicus showed no haemolysis on blood agar plate while V. hollisae showed a clear zone of haemolysis (β-hemolysis). This present study reveals that the samples collected from the study area did not show the presence of V.mimicus.