S. typhi with transferable chloramphenicol resistance isolated in Chandigarh during 1983-87.

Plasmid mediated chloramphenicol resistance in S. Typhi has been reported since the outbreak in Kerala in 1972 from India. 876 strains of S. typhi isolated at Chandigarh during Jan 1983 to July 1987 were investigated for the incidence of chloramphenicol resistance. In 1983 34% of the total isolated were resistant to chloramphenicol, in 1984 24%, during 1985 5% & while in 1986 2% of the strains showed chloramphenicol resistance. The resistant strain showed chloramphenicol resistance. The resistant strains had an minimum inhibitory concentration of 64-128 ug/ml for chloramphenicol. All the resistant strains showed multiple drug resistance with the resistance pattern CSSuT. Of these 50 strains were studied for their mechanism of resistance by conjugation experiments which showed that CSSUT pattern could be transferred to E. coli J-53 and E. coli J-62 in primary and secondary transfer experiments indicating that the resistance was carried on a transferable plasmid.