SRINIVASA RAO, T(MAJOR)MADHAVA RAO, TRAMANI PUSHPA, R.N.ASWANI KUMAR, KSUBHASHINI, NELAPATI2020-11-042020-11-042020-08https://krishikosh.egranth.ac.in/handle/1/5810154377THESESHuman contact with and consumption of fishes presents hazards from a range of bacterial zoonotic infections. The present study was undertaken to characterize Arcobactaer spp., Aeromonas spp. and V. vulnificus of fresh water, estuarine/ brackish and marine origin based on cultural isolation. A total of 420 samples comprising fish and prawn samples from fresh (70 each), marine (70 each) and estuarine environments (70 each) were analyzed to characterize Arcobacter spp., Aeromonas spp. and V. vulnificus and further these samples were screened for antibiotic residues by HPLC. Overall prevalence of Arcobacter spp. was found to be 12.61% (53/420). Out of the 53 Arcobacter spp. isolates, m-PCR revealed 38 (56.71%) to be A. butzleri, 3 (4.48%) to be A. cryaerophilus and 12 (17.91%) to be A. skirrowii. Out of the 53 Arcobacter spp. isolates, virulence genes mviN, irgA, hecA, cj1349, tlyA, pldA, hecB, ciaB and cadF were detected in 75.47%, 9.43%, 3.77%, 30.18%, 98.11%, 92.45%, 11.32%, 94.33% and 81.13% of Arcobacter spp. isolates, respectively. Antibiogram profile of 53 Arcobacter spp. isolates revealed natural resistance towards penicillin-G (100%); resistance to vancomycin (75.47%), nalidixic acid (26.42%), erythromycin (18.87%), cefixime and kanamycin (5%) and co-trimoxazole (3.77%). ESBL production was confirmed in 28 Arcobacter spp. isolates by both phenotypic and molecular methods and blaTEM was the only β-lactamase gene detected in all the 28 isolates. A greater degree of molecular heterogeneity was observed among ESBL positive Arcobacter butzleri (16) and A. skirrowii (12) isolates, respectively by ERIC-PCR and REP-PCR. The discriminatory power of the two typing methods for Arcobacter spp. was found to be highly significant (>0.90) i.e. one. Overall prevalence of Aeromonas spp. was found to be 26.42% (111/420). Out of 111 Aeromonas spp. isolates, m-PCR revealed 98 (88.28%) to be A. veroni, 9 (8.10%) to be A. hydrophila, 2 (1.80%) A. media and 2 (1.80%) A. caviae. Out of 111 Aeromonas spp. isolates, virulence genes act, ast, alt, ahyB, fla, lip, aer, ser, gcat and exu were detected in 53.15%, 4.5%, 5.4%, 9.9%, 0.9%, 22.52%, 16.21%, 2.7% 5.4 % and 15.31% of isolates, respectively. Antibiogram profile of 111 Aeromonas spp. isolates revealed natural resistance towards penicillin-G (100%) and resistance to vancomycin (63.06%) and nalidixic acid (50.45%). ESBL production was confirmed in 12 Aeromonas spp. isolates by both phenotypic and molecular methods and blaTEM was the only β-lactamase gene detected in all 12 isolates. A greater degree of molecular heterogeneity was observed among 12 ESBL positive Aeromonas spp. isolates from different sources as 12 different genotypes were observed by ERIC-PCR and REP-PCR. The discriminatory power of the two typing methods for Arcobacter spp. was found to be highly significant (>0.90) i.e. one. Overall prevalence of V. vulnificus was found to be 6.19% (26/420). All the V. vulnificus isolates carried vvhA gene and none of the isolates were belonging to Bt2 or serovar E. All the V. vulnificus isolates belonged to Bt1. Antibiogram profile of 26 V. vulnificus isolates revealed natural resistance for penicillin-G (100%) and resistance to vancomycin (61.54%), erythromycin (46.15%), cefixime (46.15%) and nalidixic acid (30.77%). ESBL production was confirmed in 17 V. vulnificus isolates by both phenotypic and molecular methods and blaTEM gene was the predominant gene in 16 isolates and blaSHV gene was detected in only one V. vulnificus isolate. A greater degree of molecular heterogeneity was observed among 17 ESBL positive V. vulnificus isolates from different sources as 16 and 17 different genotypes were observed under ERIC-PCR and REP-PCR, respectively. The discriminatory power of the two typing methods for V. vulnificus isolates was found to be highly significant (>0.90) i.e. 0.9926 and one for ERIC and REP-PCR, respectively. Cluster analysis revealed a greater degree of homogeneity and heterogeneity among different isolates (Arcobacter spp., Aeromonas spp. and V. vulnificus) recovered from various sources and indicating that there is a chance of cross-contamination particularly in the fish markets. All the fish and shellfish samples were negative for antibiotic residues by HPLC.EnglishThesis