PBP4 activity and its overexpression are necessary for PBP4-mediated high-level β-lactam resistance
PBP4 activity and its overexpression are necessary for PBP4-mediated high-level β-lactam resistance
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DOI：
10.1093/jac/dkx531
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发表时间：
2018-05-01
影响因子：
5.2
通讯作者：
Chatterjee, Som S.
中科院分区：
文献类型：
--
作者：
Basuino, Li;Jousselin, Ambre;Chatterjee, Som S.
背景：PBP 4通常被认为对金黄色葡萄球菌的高水平β-内酰胺耐药性不重要。PBP 4的突变与沙门氏菌天然菌株中β-内酰胺的不敏感性有关。金黄色的我们之前已经证明PBP 4可以介导在β-内酰胺抗生素中传代的实验室产生的菌株中的高水平β-内酰胺耐药性。pbp 4启动子中上调其表达的突变和PBP 4活性位点周围的错义突变在传代菌株中以高频率检测到，表明PBP 4在抗性中起关键作用。这些突变如何参与PBP 4提供高水平β-内酰胺抗性的能力尚不清楚。目的：确定PBP 4的酶活性是否是高水平β-内酰胺抗性所必需的，并研究PBP 4相关突变如何提供β-内酰胺抗性。通过在PBP 4的活性位点引入丝氨酸到丙氨酸的点突变，使PBP 4的催化活性丧失（Ser-75 -> Ala）在代表性的和充分研究的传代菌株CRB中。将在CRB中检测到的pbp 4启动子和错义突变单独和组合地在WT菌株中重构。通过群体分析评价所得菌株的β-内酰胺抗性。细菌肽聚糖组成的pbp 4突变体进行了评估，并没有使用LC.Results抗生素治疗：PBP 4灭活赋予完全β-内酰胺敏感性的CRB。PBP 4错义突变单独重建不赋予β-内酰胺抗性，但与pbp 4启动子突变协同作用。类似的协同作用的pbp 4突变被观察到在增强的肽聚糖交联抗生素treatment.Conclusions：PBP 4的活性和过度表达都有助于高水平的β-内酰胺耐药。
Background: PBP4 is typically considered unimportant for conferring high-level beta-lactam resistance in Staphylococcus aureus. Mutations in PBP4 have been associated with beta-lactam non-susceptibility among natural strains of S. aureus. We have previously shown that PBP4 can mediate high-level beta-lactam resistance in laboratory-generated strains passaged in beta-lactam antibiotics. Mutations in the pbp4 promoter that up-regulate its expression and missense mutations that surround PBP4's active site were detected in high frequencies among passaged strains, suggesting PBP4 plays a key role in resistance. How these mutations participate in PBP4's ability to provide high-level beta-lactam resistance is unknown.Objectives: To determine whether enzymatic activity of PBP4 is required for high-level beta-lactam resistance and to investigate how the pbp4-associated mutations provide beta-lactam resistance.Methods: The catalytic activity of PBP4 was disabled through introduction of a serine to alanine point mutation in its active site (Ser-75 -> Ala) in a representative and well-studied passaged strain, CRB. pbp4 promoter and missense mutations detected in CRB were reconstituted in a WT strain individually and in combination. beta-Lactam resistance of the resultant strains was evaluated by population analysis. Bacterial peptidoglycan composition of the pbp4 mutants was evaluated with and without antibiotic treatment using LC.Results: PBP4 inactivation imparted complete beta-lactam susceptibility of CRB. Reconstitution of PBP4 missense mutations alone did not impart beta-lactam resistance, but did so in synergism with pbp4 promoter mutation. A similar synergistic interaction of pbp4 mutations was observed in enhanced peptidoglycan cross-linking upon antibiotic treatment.Conclusions: PBP4's activity and overexpression both contribute to high-level beta-lactam resistance.