【摘要】 采用质粒及其酶切片段的指纹分析,配合以生化反应、血清学鉴定、最小抑菌浓度（MIC）测定,就我院一次鼠伤寒沙门氏菌的暴发流行中任选的7个菌株进行了分子分析。所有流行株均有相同的生化反应谱,血清学鉴定均属O₄Hi型。按MIC结果及质粒指纹分析,可将这七个株分成两组,甲组:5个株耐青霉素（PC,>500mg/ml）,氨苄青霉素（Ap,>500μg/ml）,头孢唑啉（Cz,16μg/ml）,红霉素（Er,>500μg/ml）,氯霉素（Cm,250μg/ml）,链霉素（Sm,>500μg/ml）,卡那霉素（Km,>500μg/ml）及四环素（Tc,>500μg/ml）8种抗生素。乙组:2个菌株,对6种药的MIC与甲组完全相同,但对Km及Cz的MIC分別为8μg/ml及1μg/ml。通过质粒转化试验,证明这些耐药基因均集中于一139kb的大质粒p139上。乙组耐药基因集中于一121kb的大质粒p121上。菌株SM489的变异株缺p139质粒,它的表型也呈全敏感状态,仅对红霉素仍有部分耐药性（64μg/ml）。乙组株的p121质粒比甲组株的p139质粒少18Kb,使该菌对Km及Cz由耐药变为敏感。将含p139及p121的二个转化子再经EeoRI及Hind Ⅲ內切酶切割,证实它们的绝大部分片段是相同的。用EcoRI切出的p121中24Kb片段不存在于p139中,而p139中有3.5、12.5及26kb的新片段,说明p121的24kb片段插入了抗Km及Cf基因的18kb,后者具有2个E. coRI切点。以上结果说明在流行中质粒有演变。即使是甲组株中同是p139质粒,酶切后也发现有的株缺少1kb。更多还原

【Abstract】 Our perpose in the present report was to analyse the R-plasmids and their fragments harburing in Salmonella typhimurium epidemics in hospital to find their molecular differenses. 7 strains were randumly studied from 23 wild epidemics of S. typhimuriurn. They were identical in biochemical pattern, their serotype are O₄Hi. According to MIC resuhs and plasmid fingerprints, the 7 strains were arranged into two groups: The first group of 5 strains resistant to penicillin （pc,>500 μg/ml）, Ampicillin （Ap,>500μg/ml）, Cefazolin （Cz, 16μg/ml）, Erythromycin（Er, >500μg/ml）, ChloramphenicoJ （Cm, 250μg/ml）, Streptomycin （Sm,>500μg/ml）, Kanamycin （Km,>500μg/ml） and Tetracyclin, （Tc, >500μg/ml）. It was proved by transformation test that the 8 resistant genes were on a 139 kb large plasmid p139. The second group of two strains were resistant to 6 of that 8 antibiotics, but were sensitive to km and Cz with MIC 8μg/ml and 1μg/ml respectively, their genes were on a 121 kb large plasmid p121.The plasmid p121 which was sensitive to km and Cz was less 18 kb than p139 The most of fragments from these two transformants were identical after cutting by EcoRl and HindIll, but a 24 kb fragment from p121 did not exist in plasmid p139, which had new fragments: 26, 12.5 and 3.5 kb. It suggested that the 24 kb fragment code for Km and Cz transferred into the 18 kb fragment which reformed the 3 new fragments. The plasmids in first group were also not exactly identical, one was showed to be 1 kb longer than the others.更多还原