Multidrug resistant Salmonella typhi in asymptomatic typhoid carriers among food handlers in Namakkal district, Tamil Nadu.

PURPOSE: to screen Salmonella typhi in asymptomatic typhoid carriers and to find out drug resistance and ability of the strains to transmit drug resistance to other bacteria.

METHODS

Cultural characters, biochemical tests, antibiotic sensitivity test (disc diffusion), agarose gel electrophoresis, and conjugation protocols were done. Thirty five stool samples were collected from the suspected food handlers for the study.

RESULTS

Among 35 samples, (17.14%) yielded a positive result. Out of these 4 (20.0%) were women and 2 (13.33%) were men. The isolates were tested with a number of conventional antibiotics viz, amikacin, amoxicillin, ampicillin, chloramphenicol, ciprofloxacin, co-trimaxazole, rifampicin, gentamicin, nalidixic acid, ofloxacin and tetracycline. Five isolates were having the multidrug resistant character. Four (66.66%) multidrug resistant isolates were found to have plasmids, while one (16.66%) multidrug resistant isolate had no plasmid and the chromosome encoded the resistance. Only one strain (16.66%) showed single antibiotic resistance in the study and had no plasmid DNA. The molecular weights of the plasmids were determined and found to be 120 kb. The mechanism of spreading of drug resistance through conjugation process was analyzed. In the conjugation studies, the isolates having R+ factor showed the transfer of drug resistance through conjugation, which was determined by the development of antibiotic resistance in the recipients.

CONCLUSION

This study shows that drug resistant strains are able to transfer genes encoding drug resistance.