Cheng Zishuo, Bethel Christopher R, Thomas Pei W, Shurina Ben A, Alao John-Paul, Thomas Caitlyn A, Yang Kundi, Marshall Steven H, Zhang Huan, Sturgill Aidan M, Kravats Andrea N, Page Richard C, Fast Walter, Bonomo Robert A, Crowder Michael W
Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA.
Research Services, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio, USA.
Antimicrob Agents Chemother. 2021 Mar 18;65(4). doi: 10.1128/AAC.01714-20.
Metallo-β-lactamases (MBLs) are a growing clinical threat because they inactivate nearly all β-lactam-containing antibiotics, and there are no clinically available inhibitors. A significant number of variants have already emerged for each MBL subfamily. To understand the evolution of imipenemase (IMP) genes () and their clinical impact, 20 clinically derived IMP-1 like variants were obtained using site-directed mutagenesis and expressed in a uniform genetic background in strain DH10B. Strains of IMP-1-like variants harboring S262G or V67F substitutions exhibited increased resistance toward carbapenems and decreased resistance toward ampicillin. Strains expressing IMP-78 (S262G/V67F) exhibited the largest changes in MIC values compared to IMP-1. In order to understand the molecular mechanisms of increased resistance, biochemical, biophysical, and molecular modeling studies were conducted to compare IMP-1, IMP-6 (S262G), IMP-10 (V67F), and IMP-78 (S262G/V67F). Finally, unlike most New Delhi metallo-β-lactamase (NDM) and Verona integron-encoded metallo-β-lactamase (VIM) variants, the IMP-1-like variants do not confer any additional survival advantage if zinc availability is limited. Therefore, the evolution of MBL subfamilies (i.e., IMP-6, -10, and -78) appears to be driven by different selective pressures.
金属β-内酰胺酶（MBLs）对临床的威胁日益增大，因为它们能使几乎所有含β-内酰胺的抗生素失活，且目前尚无临床可用的抑制剂。每个MBL亚家族都已出现了大量变体。为了解亚胺培南酶（IMP）基因的进化及其临床影响，通过定点诱变获得了20个临床来源的IMP-1样变体，并在大肠杆菌DH10B菌株的统一遗传背景中进行表达。携带S262G或V67F替换的IMP-1样变体菌株对碳青霉烯类抗生素的耐药性增加，对氨苄西林的耐药性降低。与IMP-1相比，表达IMP-78（S262G/V67F）的菌株在最低抑菌浓度（MIC）值上变化最大。为了解耐药性增加的分子机制，开展了生化、生物物理和分子建模研究，以比较IMP-1、IMP-6（S262G）、IMP-10（V67F）和IMP-78（S262G/V67F）。最后，与大多数新德里金属β-内酰胺酶（NDM）和维罗纳整合子编码的金属β-内酰胺酶（VIM）变体不同，如果锌的可利用性有限，IMP-1样变体不会赋予任何额外的生存优势。因此，MBL亚家族（即IMP-6、-10和-78）的进化似乎是由不同的选择压力驱动的。
