Attenuation of penicillin resistance in a peptidoglycan O-acetyl transferase mutant of Streptococcus pneumoniae
Attenuation of penicillin resistance in a peptidoglycan O-acetyl transferase mutant of Streptococcus pneumoniae
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DOI：
10.1111/j.1365-2958.2006.05340.x
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发表时间：
2006-09-01
影响因子：
3.6
通讯作者：
Tomasz, Alexander
中科院分区：
文献类型：
--
作者：
Crisostomo, M. Ines;Vollmer, Waldemar;Tomasz, Alexander
肺炎链球菌临床分离株的青霉素耐药性水平不仅取决于青霉素结合蛋白（PBP）亲和力的降低，还取决于修饰细胞壁前体干肽结构的酶的功能。我们使用水手诱变来寻找额外的遗传决定因素，这些决定因素可能会进一步减弱细菌的青霉素耐药性水平。高度青霉素耐药的肺炎链球菌菌株Pen6的mariner突变体显示出青霉素最低抑菌浓度(MIC)从6降低至0.75μgml(-1)。在将突变（临时命名为 adr，耐药性衰减因子）引入青霉素耐药肺炎球菌的主要流行性克隆的代表中后，也观察到青霉素 MIC 降低。耐药水平的减弱是β-内酰胺类药物所特有的。 adr突变体保留了未改变（低亲和力）的PBP、未改变的murM基因和未改变的细胞壁干肽组成，但该突变体对外源溶菌酶变得过敏，并且互补实验表明这两种表型——抗性降低和溶菌酶敏感性降低——都与有缺陷的adr基因有关。 DNA 序列比较和细胞壁化学分析确定 adr 是肺炎球菌肽聚糖 O-乙酰酶的结构基因。
The level of penicillin resistance in clinical isolates of Streptococcus pneumoniae depends not only on the reduced affinity of penicillin binding proteins (PBPs) but also on the functioning of enzymes that modify the stem peptide structure of cell wall precursors. We used mariner mutagenesis in search of additional genetic determinants that may further attenuate the level of penicillin resistance in the bacteria. A mariner mutant of the highly penicillin-resistant S. pneumoniae strain Pen6 showed reduction of the penicillin minimum inhibitory concentration (MIC) from 6 to 0.75 mu g ml(-1). Decrease in penicillin MIC was also observed upon introduction of the mutation (named provisionally adr, for attenuator of drug resistance) into representatives of major epidemic clones of penicillin-resistant pneumococci. Attenuation of resistance levels was specific for beta-lactams. The adr mutant has retained unchanged (low affinity) PBPs, unaltered murM gene and unchanged cell wall stem peptide composition, but the mutant became hypersensitive to exogenous lysozyme and complementation experiments showed that both phenotypes - reduced resistance and lysozyme sensitivity - were linked to the defective adr gene. DNA sequence comparison and chemical analysis of the cell wall identified adr as the structural gene of the pneumococcal peptidoglycan O-acetylase.