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ThesisItem Open Access Characterization of MDR Enterococcus species of animal, human and environmental origin with special emphasis on vancomycin resistance(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517502. (A.P.) INDIA, 2019-11) CHAITANYA, GOTTAPU; BINDU KIRANMAYI, CH (MAJOR); SRINIVASA RAO, T; ASWANI KUMAR, KThe present study was undertaken to characterize Enterococcus species of animal, human and environmental origin based on cultural isolation. It was also aimed to determine the major antibiotic resistant genotypes (vancomycin resistance, high level aminoglycoside resistance and β- lactamase resistance), phenotypic virulence factors and virulence genes of Enterococcus species of worldwide public health importance. A total of 780 samples were collected including animals, foods of animal origin, water, human faecal, human diarrhoeic and human urine samples and were examined for presence of Enterococcus spp. i.e. E. faecalis, E. faecium, E. gallinarum and E. casseliflavus. Overall prevalence of genus Enterococcus was found to be 86.79% and the prevalence of the Enterococcus spp. in various samples ranging from 100% each in sheep rectal swabs, pig rectal swabs and human diarrhoeic samples to 55.00% in uterine discharges of cattle. Enterococci are opportunistic pathogens and cause occasional infections. Virulence gene and phenotypic virulence factors are major indicators to pathogenicity of these microorganisms. In present study, presence of phenotypic virulence factors among 608 Enterococcus isolates i.e. hemolysis of sheep RBC, slime layer formation, lipase activity, caseinase activity, biofilm formation, gelatinase, DNase activity and HA test were detected in 312 (51.31%), 243 (39.96%), 47 (7.73%), 121 (19.90%), 236 (38.81%), 141 (23.19%), 37 (6.08%) and 87 (14.30%) of Enterococcus isolates, respectively. Out of seven virulence markers investigated in Enterococcus isolates, gelE was predominant in 181 isolates (29.76%) followed by 180 asa (29.60% each), 131 hyl (21.54%), 117 ace (19.24%), 101 efaA (16.61%) and 68 cyl (11.18%). Antibiogram profiling of 608 isolates revealed a major fraction of the Enterococcus isolates to be resistant to polymixin-B (95.55%) followed by ceftazidime (93.25%), erythromycin (77.63%) and streptomycin (44.07%). A total of 179 (29.44%) isolates were positive for HLAR genes and aac(6´)Ie-aph(2˝)Ia was the only gene detected in all isolates and 127 (20.88%) isolates were positive for blaZ gene. The blaZ gene was predominantly detected in E. faecium (34.63%), followed by E. faecalis (14.38%), E. gallinarum (16.50%) and E. casseliflavus (16.66%). A total of 608 Enterococcus isolates studied, 125 Enterococcus isolates were identified as VRE genotypically. The genes VanB, VanC1 and VanC2 were detected in 14 (11.20%), 69 (55.20%) and 42 (36.60%) Enterococcus isolates, respectively. None of isolates showed VanA gene. A greater degree of heterogeneity was observed among 124 VRE isolates (one E. gallinarum isolate did not yield any bands for both ERIC-PCR and REP- PCR) of different species from different sources as revealed by presence of 122 genotypes and 123 genotypes by ERIC and REP-PCR analysis, respectively. Nineteen different E. faecalis, 15 E. faecium, 57 E. gallinarum and 31 E. casseliflavus subtypes were differentiated by ERIC-PCR, whereas 21 different E. faecalis, 15 E. faecium, 56 E. gallinarum and 31 E. casseliflavus subtypes by REP- PCR. Genotyping of VR Enterococcus species by ERIC- PCR and REP- PCR was found to be highly significant since discriminatory power >0.9 are considered highly significant (0.9997 for ERICPCR and 0.9999 for REP-PCR. Cluster analysis also revealed a great degree of homogeneity among some VRE isolates recovered from different sources and implied at the chance of cross-contamination of foods of animal origin