ALTERED PENICILLIN-BINDING PROTEINS IN METHICILLIN-RESISTANT STRAINS OF STAPHYLOCOCCUS-AUREUS
ALTERED PENICILLIN-BINDING PROTEINS IN METHICILLIN-RESISTANT STRAINS OF STAPHYLOCOCCUS-AUREUS
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DOI：
10.1128/aac.19.5.726
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发表时间：
1981-01-01
影响因子：
4.9
通讯作者：
TOMASZ, A
中科院分区：
文献类型：
--
作者：
HARTMAN, B;TOMASZ, A
通过使用高比活性[3H]青霉素作为试剂，比较了耐甲氧西林（MR）和甲氧西林敏感（MS）金黄色葡萄球菌的青霉素结合蛋白（PBP）。发现MR和MS菌株含有相同数量和电泳迁移率的PBP。MR菌株中甲氧西林对PBP 1、2和3的饱和需要使用数千微克/ml的抗生素；0.2 - -0.4 .mu。g的甲氧西林ml足以有效地与[3H]青霉素竞争MS菌株的PBP。另外的实验表明，这些差异很可能反映了与MS菌株相比，MR菌株的PBP亲和力大大降低。将MR菌株培养基的pH值从7.0-5.2改变，其对甲氧西林的表型抗性立即从最小抑制浓度3200 .mu下降。g/ml, pH 7.0 ~ 0.8。g/ml （pH 5.2）。在pH 5.2下培养的MR细菌中PBP对甲氧西林的亲和性检测显示，PBP与pH 7.0下培养的细菌存在相同的低亲和性。对甲氧西林的ph依赖性再敏化不能用PBP对抗生素亲和性的平行增加来解释。
The penicillin-binding proteins (PBP) of a methicillin-resistant (MR) and a methicillin-susceptible (MS) S. aureus were compared by various approaches involving the use of high-specific-activity [3H]penicillin as a reagent. The MR and MS strains were found to contain PBP of the same number and electrophoretic mobilities. Saturation of PBP 1, 2 and 3 by methicillin in the MR strain required the use of several thousands of micrograms of antibiotic/ml; 0.2-0.4 .mu.g of methicillin ml was sufficient to effectively compete with [3H]penicillin for the PBP of the MS strain. Additional experiments indicate that these differences most likely reflect a greatly decreased affinity of the PBP of the MR strain as compared to those of the MS strain. Shift of the pH of the culture medium of the MR strain from pH 7.0-5.2 resulted in an immediate drop in phenotypic resistance to methicillin (from a minimal inhibitory concentration value of 3200 .mu.g/ml at pH 7.0 to 0.8 .mu.g/ml at pH 5.2). Examination of the methicillin affinities of PBP in MR bacteria grown at pH 5.2 showed the presence of the same low-affinity PBP as in bacteria grown at pH 7.0. The pH-dependent resensitization to methicillin cannot be explained by a parallel increase in the antibiotic affinities of the PBP.