A study of drug resistance among Salmonella typhi and Salmonella paratyphi A in an endemic area, 1977-79.

Tests for antibiotic resistance were carried out on 198 strains of Salmonella typhi and S. paratyphi A isolated from cases of enteric fevers. Their minimal inhibitory concentrations for streptomycin, chloramphenicol, ampicillin, furazolidine and co-trimoxazole were estimated by plate dilution technique. Four strains of S. typhi and one strain of S. paratyphi A were found to show multiple resistance with a set pattern of resistance to chloramphenicol, streptomycin, sulphonamide, tetracycline and spectinomycin. All the five strains carried R-factors. Three of the resistant S. typhi belonged to Phage type 'O' and one was in Phage type 'A'. The single resistant S. paratyphi A belonged to Phage type '2'.