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首页> 外文期刊>Infection and immunity >Virulence of Staphylococcus aureus mutants altered in type 5 capsule production.
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Virulence of Staphylococcus aureus mutants altered in type 5 capsule production.

机译：金黄色葡萄球菌突变体的毒性改变了5型胶囊的生产。

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Most clinical isolates of Staphylococcus aureus produce microcapsules (uronic acid-containing extracellular polysaccharides) that are detectable by serologic methods but are not visible by negative staining. Among the 11 reported serotypes, capsule types 5 and 8 comprise approximately 75% of all isolates. Transposon mutagenesis was performed on S. aureus to create mutants altered in capsule expression. Tn918 was introduced into the capsule type 5 strain Reynolds by filter mating, and a capsule-deficient transconjugate, JL236, was isolated. The wild-type strain was transformed with JL236 chromosomal DNA to confirm that transfer of the appropriate-size chromosomal fragment containing Tn918 generated a capsule-deficient transformant. Strain Reynolds was mutagenized with ethyl methanesulfonate to obtain a capsule-negative mutant (strain JL240). Capsular phenotypes were determined by colony immunoblots, antibody adsorption experiments, and transmission electron microscopy. The virulences of the parental and mutant strains in mice were compared. The 50% lethal doses for strains Reynolds, JL236, and JL240 were similar (10(8.59), 10(8.98), and 10(8.93) CFU, respectively). Animals injected intraperitoneally with either wild-type or mutant strains had comparable levels of bacteremia at 3 and 24 h after challenge. Quantitative cultures of blood and kidneys from animals challenged intravenously with sublethal doses of the S. aureus strains also showed no differences in bacterial clearance or renal abscess formation. These studies indicate that the type 5 S. aureus microcapsule does not promote bacterial virulence in the animal models tested.
机译：大多数金黄色葡萄球菌临床分离株会产生微胶囊（含尿酸的细胞外多糖），可通过血清学方法检测到，但通过负染色看不到。在报告的11种血清型中，5型和8型胶囊占所有分离株的约75％。对金黄色葡萄球菌进行转座子诱变以产生胶囊表达改变的突变体。通过过滤器交配将Tn918引入5型胶囊雷诺菌株中，并分离出缺乏胶囊的反式结合物JL236。用JL236染色体DNA转化野生型菌株，以确认包含Tn918的适当大小的染色体片段的转移产生了胶囊缺陷型转化子。用甲磺酸乙酯诱变雷诺菌株，得到胶囊阴性突变体（菌株JL240）。通过集落免疫印迹，抗体吸附实验和透射电子显微镜确定胶囊的表型。比较了亲本和突变株在小鼠中的毒力。雷诺，JL236和JL240菌株的50％致死剂量相似（分别为10（8.59），10（8.98）和10（8.93）CFU）。腹膜内注射野生型或突变株的动物在攻击后3小时和24小时具有可比的菌血症水平。用亚致死剂量的金黄色葡萄球菌静脉内攻击的动物的血液和肾脏的定量培养物，在细菌清除率或肾脓肿形成方面也没有差异。这些研究表明，在所测试的动物模型中，金黄色葡萄球菌5型微囊不促进细菌毒力。

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