Plasmid analysis and antibiotic resistance pattern measurement of Shigella in Chengdu]

A total of 81 strains of Shigella isolated from sporadic cases and cases in an outbreak of Shigella sonnei infection was analysed by plasmid profiles and antibiotic resistance patterns. The strains had a high resistance patterns. The strains had a high resistance of ampicillin, tetracycline, trimethoprim-sulfamethoxazole and chloramphenicol; while 97.2% of the strains were susceptible to gentamicin, kanamycin. The results showed that 50% of the strains harbored plasmid patterns within each species, which indicated that many genetically different strains of Shigella were responsible for dysentery epidemics in Chengdu. According to the results of the plasmid analysis and antibiotic resistance pattern measurement made in the outbreak strains, it was clearly seen that most of the strains were similar or fundamentally similar, which suggested that one or two strains with genetical homology were the main causative agent for the outbreak. We think that plasmid profiles and antibiotic resistance patterns are applicable to the identification of the outbreak strains of dysentery as an efficient epidemiologic tool.