Plasmid associated antibiotic resistance in Vibrios isolated from coastal waters of Kerala

The present study was aimed to detect the plasmid profile, the role of plasmid associated multiple antibiotic resistance of Vibrios isolated from coastal waters of Kerala. The isolated plasmids from antibiotic resistant Vibrios were tested for the presence of integrons using polymerase chain reaction (PCR) to elucidate the presence of plasmid borne integron, a key element in horizontal gene transfer. 100 isolates of Vibrios from water samples of shrimp farms and coastal landing sites were tested for the antibiogram profile to 22 antibiotics and the presence of the plasmids. Antibiotic resistance studies revealed that 78% were expressing multiple antibiotic resistance (MAR), defined as the isolates having resistant to more than three resistance determinants. The levels of resistance exhibited by isolates to specific antibiotics vary between 94 % and 6%. In the plasmid profiling test, only 17 isolates (21%) harbored plasmid DNA which ranged in size from 1.4 to 25 kb, separating the isolates into various plasmid profiles. Interestingly it was observed from the plasmid profiling that 11 strains among them had a single plasmid, 4 strains were with two plasmids and one each of having three and four plasmids. The role of native plasmids in antibiotic resistance in Vibrios was confirmed by isolation and transformation of the plasmids in E.coli DH5α, followed by antibiotic resistance assay. Both the plasmids and the associated antibiotic resistance of selected isolates could be transferred to a recipient by transformation and conjugation. The study demonstrates the plasmid-mediated drug resistance as a contributor to the antibiotic resistance in Vibrios of the aquatic system and their ability to disseminate the resistance by means of transformation, conjugation and by horizontal gene transfer element like integrons. Antibiotic resistance marker and its location were confirmed from the resistant plasmids from Vibrio isolates by using curing protocols. As in many developing countries, antimicrobial resistance epidemiology is still in the infancy stage in the locality of the study. To our knowledge, there are no reports available on the plasmid mediated multiple antibiotic resistance in Vibrio isolates from coastal waters of Kerala and our study on plasmid profiling will provide a current baseline profile of plasmid mediated resistance of Vibrios from coastal waters in Kerala and thereby will provide a significant insight about Indian scenario.