Genetic analysis of the β-lactamases of Mycobacterium tuberculosis and Mycobacterium smegmatis and susceptibility to β-lactam antibiotics
Genetic analysis of the β-lactamases of Mycobacterium tuberculosis and Mycobacterium smegmatis and susceptibility to β-lactam antibiotics
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DOI：
10.1099/mic.0.27629-0
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发表时间：
2005-02-01
期刊：
影响因子：
2.8
通讯作者：
Pavelka, MS
中科院分区：
文献类型：
--
作者：
Flores, AR;Parsons, LM;Pavelka, MS
分枝杆菌产生β-内酰胺酶，并且对β-内酰胺抗生素具有内在抗性。除β-内酰胺酶外，细胞被膜渗透性和某些肽聚糖生物合成酶的变异被认为有助于这些生物体中的β-内酰胺耐药性。为了研究这些额外的机制，在致病性结核分枝杆菌菌株H37 Rv和模式生物耻垢分枝杆菌菌株PM 274中产生了主要β-内酰胺酶BlaC和BlaS的突变体。突变体M.结核分枝杆菌PM 638（DeltablaC 1）和M.通过纸片扩散法和最小抑菌浓度（MIC）测定，结果表明，smeglycerPM 759（DeltablaS 1）对β-内酰胺类抗生素的敏感性增加。通过纸片扩散试验测定的突变体对青霉素型β-内酰胺类抗生素的敏感性，与头孢菌素型β-内酰胺类抗生素相比，受影响最大。分枝结核分枝杆菌突变株无β-内酰胺酶活性; smeglastin突变体具有残留的1型β-内酰胺酶活性。我们在M中鉴定了一个编码推定的头孢菌素酶的基因blaE。恶臭M.耻垢病，PM 976（DeltablaS 1 DeltablaE：：res），没有检测到β-内酰胺酶活性，但其对β-内酰胺抗生素的敏感性与DeltablaS 1亲本菌株PM 759没有显著差异。本研究中产生的突变体将有助于确定其他β-内酰胺耐药机制的贡献，此外还可作为研究这些生物体中肽聚糖生物合成生物学的工具。
Mycobacteria produce beta-lactamases and are intrinsically resistant to beta-lactam antibiotics. In addition to the beta-lactamases, cell envelope permeability and variations in certain peptidoglycan biosynthetic enzymes are believed to contribute to beta-lactam resistance in these organisms. To allow the study of these additional mechanisms, mutants of the major beta-lactamases, BlaC and BlaS, were generated in the pathogenic Mycobacterium, tuberculosis strain H37Rv and the model organism Mycobacterium smegmatis strain PM274. The mutants M. tuberculosis PM638 (DeltablaC1) and M. smegmatis PM759 (DeltablaS1) showed an increase in susceptibility to beta-lactam antibiotics, as determined by disc diffusion and minimal inhibitory concentration (MIC) assays. The susceptibility of the mutants, as assayed by disc diffusion tests, to penicillin-type beta-lactam antibiotics was affected most, compared to the cephalosporin-type beta-lactam antibiotics. The M. tuberculosis mutant had no detectable beta-lactamase activity, while the M. smegmatis mutant had a residual type 1 beta-lactamase activity. We identified a gene, blaE, encoding a putative cephalosporinase in M. smegmatis. A double beta-lactamase mutant of M. smegmatis, PM976 (DeltablaS1DeltablaE::res), had no detectable beta-lactamase activity, but its susceptibility to beta-lactam antibiotics was not significantly different from that of the DeltablaS1 parental strain, PM759. The mutants generated in this study will help determine the contribution of other beta-lactam resistance mechanisms in addition to serving as tools to study the biology of peptidoglycan biosynthesis in these organisms.