Kornblum J, Hartman B J, Novick R P, Tomasz A
Eur J Clin Microbiol. 1986 Dec;5(6):714-8. doi: 10.1007/BF02013311.
Plasmid pRN3208, thermosensitive for replication, and carrying the erythromycin transposon Tn551, was used for insertional inactivation of methicillin resistance in a highly and homogeneously resistant strain of Staphylococcus aureus. Two kinds of insertionally inactivated cells were obtained. Cultures of the major class contained highly methicillin resistant cells with a frequency of about 10(-3) to 10(-4), produced DNA with methicillin resistance transforming activity, and also produced penicillin binding protein 2a, the 78 kd low affinity penicillin binding protein characteristic of methicillin resistant Staphylococcus aureus, in apparently normal quantities. The single member of class B had no detectable methicillin resistant cells (less than 10(-8)) with an MIC greater than 1 micrograms/ml, contained no DNA with methicillin resistant transforming activity and no penicillin binding protein 2a. The data suggest that in the class A cells insertional inactivation did not affect the structural gene(s) of methicillin resistance but a regulatory locus or loci needed for the homogeneous expression of resistance.
质粒pRN3208对复制具有热敏性，并携带红霉素转座子Tn551，用于在高度均一耐药的金黄色葡萄球菌菌株中对甲氧西林耐药性进行插入失活。获得了两种插入失活的细胞。主要类型的培养物含有甲氧西林高度耐药细胞，频率约为10^(-3)至10^(-4)，产生具有甲氧西林耐药转化活性的DNA，并且还产生青霉素结合蛋白2a，这是甲氧西林耐药金黄色葡萄球菌特有的78kd低亲和力青霉素结合蛋白，其含量显然正常。B类的单一成员没有可检测到的甲氧西林耐药细胞（小于10^(-8)），其MIC大于1微克/毫升，不含有具有甲氧西林耐药转化活性的DNA，也没有青霉素结合蛋白2a。数据表明，在A类细胞中，插入失活并未影响甲氧西林耐药性的结构基因，而是影响了耐药性均匀表达所需的一个或多个调控位点。
