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Subject: Aquaculture × End date: 2021 × Start date: 2020 × Thesis Type: M.F.Sc ×
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    ThesisItemOpen Access
    CHARACTERIZATION AND ANTIMICROBIAL RESISTANCE OF AEROMONAS SPECIES ISOLATED FROM CULTURED FRESHWATER FISHES
    (SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2020-12) SRUTHI, PERLA; Neeraja, T (MAJOR); Haribabu, P; Balasubramanian, A
    Pathogenic Aeromonas species are causing significantly high mortalities and economic losses among the cultured freshwater fish in India and Andhra Pradesh. The aim of the present study was to identify the Aeromonas species isolated from cultured freshwater fishes majorly exhibiting bacterial haemorrhagic septicaemia, abdominal dropsy, tail rot and fin rot in two districts viz., West Godavari and SPSR Nellore districts of Andhra Pradesh, India. The diseased fish species collected from farms were Catla catla (catla), Labeo rohita (rohu), Piaractus brachypomus (pacu) and Pangasius hypophthalmus (pangas). Further, the resistance of the isolated Aeromonas spp. to the currently available antimicrobial therapeutics was determined. In the present study, 15 species of Aeromonas were isolated viz., Aeromonas allosacharrophila (n=3), A. aquariorum (n=2), A. caviae (n=1), A. enchelia (n=1), A. jandaei (n=3), A. media (n=2), A. molluscorum (n=3), A. piscicola (n=1), A. popoffii (n=3), A. sobria (n=3), A. schubertii (n=6), A. tecta (n=9), A. trota (n=3), A. veronii biovar sobria (n=5) and A. veronii biovar veronii (n=13). The Aeromonas species isolated on RS medium and GSPA medium were identified and characterized by conventional biochemical tests. The study on prevalence of Aeromonas spp. was carried out for a period of 7 months from September 2019 to March 2020 in the above two districts revealed that the highest prevalence was recorded in A. veronii bv. veronii. Significantly higher prevalence (P 0.05) with the latter species. Further, prevalence of Aeromonas spp. were significantly different (p <0.05) with respect to fish species and geographic location. In vitro antibiotic resistance study revealed that all the isolates of 15 Aeromonas spp. were highly resistant to ampicillin, amoxyclav and oxytetracycline. Further, all the Aeromonas spp. were found multiple antibiotic resistance (MAR). The MAR index of more than 0.2 was observed in all the isolates of Aeromonas spp. except A. piscicola. It indicates that these Aeromonas spp. might have originated from high risk sources of contamination. Haemolytic activity assay revealed that A. veronii bv. sobria (60%), A. aquariorum (50%), A. jandaei (33.3%), A. sobria (33.3%) and A. tecta (22.22%) were found to be β-haemolytic. However, majority of the Aeromonas spp. isolates were found α- haemolytic.
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    ThesisItemOpen Access
    SURVEILLANCE ON BACTERIAL DISEASES OF CULTURED INDIAN MAJOR CARPS IN ANDHRA PRADESH, INDIA
    (SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2020-06) SRIVIDYA, R; Neeraja, T(MAJOR); Haribabu, P; Dhanapal, K
    Bacterial fish diseases were considered to be the main cause of high mortalities and economic losses among the cultured freshwater fish in Andhra Pradesh. The aim of the present study was to identify the bacterial strains isolated from farm raised Indian major carps majorly exhibiting bacterial haemorrhagic septicaemia, abdominal dropsy, tail rot and fin rot in two districts viz., SPSR Nellore and West Godavari districts of Andhra Pradesh, India. Further, the susceptibility of the isolated bacterial strains to the currently available antimicrobial therapeutics was determined. In the present study, the pathogenic bacteria isolated were species of Aeromonas, Pseudomonas and Enterobacteriacea family. 7 species of Aeromonas viz., Aeromonas hydrophila, A. tecta, A. caviea, A. sobria, A. veronii A. schubertii and A. encheleia; 4 species of Pseudomonas viz., Pseudomonas sp., Pseudomonas stutzeri, P. diminuta and P. fluoroscenes; 5 species of Enterobacteriacea family viz., Citrobacter freundi, Serratia rubidaea, S. fonticola, Klebsiella pneumoniae ssp pneumniae and Enterobacteriacea group were identified and characterized by conventional biochemical tests. The prevalence study carried out for a period of one year from July 2018 to June 2019 in the above two districts revealed the dominance of aeromoniasis caused by Aeromonas spp. Significantly higher prevalence (P 0.05) with that of aeromoniasis. Further, prevalence of bacterial diseases did not vary significantly (P > 0.05) with respect to fish species, geographic location and seasonality. In vitro antibiotic sensitivity study revealed that gentamicin, ciprofloxacin, amikacin and trimethoprim were found to be more effective against Aeromonas sp., Pseudomonas sp. and Enterobacteriaceae family. Multiple antibiotic resistance (MAR) study showed that all the species of Pseudomonas and Enterobacteriaceae family were MAR. Among Aeromonas sp., A. tecta and A. caviea were 100% MAR, however 80% of A. sobria, A. veronii and A. schubertii showed MAR and 50% of A. hydrophila strains only showed MAR. The MAR index of more than 0.2 was observed in all the bacterial strains of Aeromonas, Pseudomonas and Enterobacteriaceae family indicated that these bacterial strains might have originated from high risk sources of contamination. Haemolytic activity assay revealed that A. veronii (80%), A. schubertii, (60%), A. sobria (40%) and A. tecta (33.3%) were found to be β-haemolytic.