Antimicrobial resistance and R factors in Salmonella isolated from humans and animals in Georgia and South Carolina.

Three hundred and five strains of Salmonella isolated from humans and 152 strains isolated from animals in Georgia and South Carolina during 1973 were examined for resistance to 14 antimicrobial agents. S typhimurium was the most frequently isolated serotype (30% of human isolates and 13% of animal isolates). The overall incidence of antimicrobial resistance was 16% in human starins and 21% in animal strains. The most commonly found resistance were to streptomycin (11% in human strains and 16% in animal strains) and tetracycline (10% in both human and animal isolates). A higher prevalence of resistance to streptomycin, spectinomycin, and nitrofurantoin, which are currently used primarily in veterinary medicine, was found in animal Salmonella. Conversely, resistance to ampicillin, cephalothin, and kanamycin, which are used mainly in human medicine, was found more frequently in human Salmonella. No resistance to nalidixic acid, gentamicin, tobramycin, rifampin, or trimethoprim was detected. Sixty-five percent of resistant strains from humans and 60% of resistant strains from animals transferred their resistance patterns partially or in toto.