이질균의 R Plasmid의 유전적 특성

Abstract

In order to choose adequate antimicrobial drugs for shigellosis and to know the mechanisms of durg resistances and molecular epidemiologic data, 67 strains of Shigella flexneri and 11 strains of Shigella sonnei were tested for the antimicrobial susceptibilities, conjugal transfer of R plasmids, incompatibility grouping, plasmid DNA profiles and the recombinations of resistance genes. In S. flexneri, 88.1 to 97% of the strains were susceptible to kanamycin(Km) and rifampicin(Rf), 76.1% of the strains were susceptible to nalidixic acid(Na) and 37.3 to 52.2% of strains to sulfisomidine(Su), trimethoprim(Tp), and cotrimoxazol(Co). In S. sonnei, 100% were susceptible to Km and Rf, and 63.6% to Na. There was no susceptible strain to Cm, Tc, Sm, and Su. In contrast to S. flexneri, many strains(81.8%) of S. sonnei were susceptible to Ap and few(0 to 9.1%) strains to Su, Tp, and Co. Most of drug resistances except to Na and Km in 50 to 100% of resistant strains were co-transferred to recipient E. coli RG488, indicationg that multiple drug resistances were R plamid mediated phenomenon. Most of R plasmids were 62.4 mega dalton(Mdal) in size and classified into the incompatibility group FⅡ. Somewhat larger plasmids, 115.6Mdal in size were frequently found in Shigella. Doubles containing both resistances of incoming plasmid and resident plasmid in incompatibility grouping were tested for the plasmid DNA profiles and the conjugations to the plasmid free recipient. According to these results, we fround that doubles had single recombinant plasmid, 64.5 Mdal in size and the mechanisms of the recombination of these resistance genes were thought to be transpositions between two plasmids.