Characterization of Escherichia coli NDM isolates with decreased susceptibility to aztreonam/avibactam: role of a novel insertion in PBP3
Characterization of Escherichia coli NDM isolates with decreased susceptibility to aztreonam/avibactam: role of a novel insertion in PBP3
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DOI：
10.1093/jac/dku568
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发表时间：
2015-05-01
影响因子：
5.2
通讯作者：
Lahiri, Sushmita D.
中科院分区：
文献类型：
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作者：
Alm, Richard A.;Johnstone, Michele R.;Lahiri, Sushmita D.
目的：NDM-1在肠杆菌科细菌中的传播对严重感染的临床治疗构成了严重的威胁。氨曲南和阿维巴坦(一种非β-内酰胺酶抑制剂)的联合应用可能提供一种亟需的治疗替代方案。这种组合对大多数含有NDM的肠杆菌科细菌有效，尽管对许多大肠杆菌分离株的活性降低。方法：采用微量肉汤稀释法进行MIC测定，并进行全基因组测序。结果：细菌对氨曲南/阿维菌素的敏感性降低并非由于阿维菌素不能抑制分离株中的丝氨酸β-内酰胺酶所致。相反，它表现为在PBP3中插入了四个氨基酸。在对氨曲南/阿维巴坦敏感性降低的不含NDM的大肠杆菌中也发现了同样的插入。构建的等位基因突变株证实，该插入降低了对氨曲南和几种头孢菌素的敏感性，但对碳青霉烯类抗生素的效力没有影响。结构分析表明，这一插入将影响β-内酰胺类药物对PBP3转肽酶口袋的可及性。结论：β-内酰胺酶的获得是肠杆菌科细菌对β-内酰胺类药物耐药的主要机制。我们已经证明，PBP3的微小变化将影响对大范围β-内酰胺类药物的敏感性。这些变化在大肠杆菌的多个MLST谱系中被鉴定出来，并在含有NDM的分离物中得到丰富。然而，尽管PBP3蛋白之间存在显著的保守性，但它们在肠杆菌科的其他关键物种中并不存在。
Objectives: The spread of NDM-1 amongst Enterobacteriaceae has highlighted a significant threat to the clinical management of serious infections. The combination of aztreonam and avibactam, a non-beta-lactam beta-lactamase inhibitor, may provide a much-needed therapeutic alternative. This combination was potent against most NDM-containing Enterobacteriaceae, although activity was diminished against many Escherichia coli isolates. These E. coli isolates were characterized to elucidate the mechanism of decreased susceptibility to aztreonam/avibactam.Methods: MIC determinations were performed using broth microdilution, and whole-genome sequencing was performed to enable sequence-based analyses.Results: The decreased susceptibility was not due to avibactam being unable to inhibit the serine beta-lactamases found in the E. coli isolates. Rather, it was manifested by a four-amino-acid insertion in PBP3. This same insertion was also found in non-NDM-containing E. coli that had reduced susceptibility to aztreonam/avibactam. Construction of an isogenic mutant confirmed that this insertion resulted in decreased susceptibility to aztreonam and several cephalosporins, but had no impact on carbapenem potency. Structural analysis suggests that this insertion will impact the accessibility of the beta-lactam drugs to the transpeptidase pocket of PBP3.Conclusions: The acquisition of beta-lactamases is the predominant mechanism of beta-lactam resistance in Enterobacteriaceae. We have demonstrated that small PBP3 changes will affect the susceptibility to a broad range of beta-lactams. These changes were identified in multiple MLST lineages of E. coli, and were enriched in NDM-containing isolates. However, they were not present in other key species of Enterobacteriaceae despite significant conservation among the PBP3 proteins.