Multidrug resistant Salmonella typhi in Calicut, south India.

Eighty S. typhi strains isolated during the period of one year (July 1989 to June 1990) were tested for susceptibility to chloramphenicol, ampicillin, cotrimoxazole, gentamicin, kanamycin, cefazolin, furazolidone and ciprofloxacin. Determination of minimum inhibitory concentration (MIC) by tube dilution method showed that the multiply resistant S. typhi strains were resistant to chloramphenicol and ampicillin up to a concentration of 1000 micrograms/ml. MIC of sulphamethoxazole was found to be 800 micrograms/ml and trimethoprim 160 micrograms/ml. The presence of R plasmid was demonstrated by resistance transfer experiments using Esch. coli K12 (F-Lac+Nal-) as the recipient. On phage typing, most of the multiresistant S. typhi isolates were found to belong to phage type E1.