Characterization of resistance plasmid of Shigella sonnei isolates from the outbreak at Cheju Island in 2000

Abstract

A large outbreak of Shigella sonnei gastrointestinal infections occurred at Cheju Island in Korea from May to August 2000. We selected 54 strains which were isolated from the primary treatment failure cases in the outbreak, and characterized the resistance-determining region of the R-plasmid. The 54 strains showed the same antimicrobial resistance patterns; resistance against ampicillin, streptomycin, tetracycline and trimethoprim-sulfamethoxazole. The resistances to ampicillin, streptomycin, and tetracycline were mediated by a conjugable plasmid of about 80 kb size, but the trimethoprim-sulfamethoxazole resistance was not transferred by plasmid. The R-determining region of the plasmid was cloned and characterized. The 8,384 bp sequences contained the resistance genes of strA, strB, tetR, tetA, and sul1in order. Fifty four isolates harbored the same sized plasmid and showed the same ribotyping patterns, which suggested the clonal spread of S. sonnei in the outbreak.