Brunetti Florencia, Gutkind Gabriel, Gao Lin, Haider Shozeb, Bonomo Robert A, Power Pablo
Universidad de Buenos Aires, Instituto de Investigaciones en Bacteriología y Virología Molecular (IBaViM), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina.
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
Antimicrob Agents Chemother. 2025 Jun 4;69(6):e0191524. doi: 10.1128/aac.01915-24. Epub 2025 May 5.
Combinations of β-lactam-diazabicyclooctane inhibitors (DBOs) like ceftazidime-avibactam (CZA) and imipenem-relebactam (IMR) have shown efficacy in treating KPC-2-producing . However, CZA-resistant strains have been identified, often linked to substitutions and/or insertions/deletions in three different loops of KPC: (i) the Ω-loop region (amino acids 164-179), (ii) the 237-243 loop; and (iii) the 266-275 loop. This study investigates the impact of the double deletion ΔG242-T243 present in KPC-14. Our results demonstrate that the lower effectiveness of CZA against KPC-14 can be explained by both increased hydrolysis of ceftazidime and a lower affinity and acylation rate by avibactam. In contrast, the IMR combination was efficient in restoring susceptibility to the KPC-14 producing-clone. Although we also observed a lower affinity and acylation rate for relebactam in KPC-14, this reduction in affinity was accompanied by a loss in the carbapenemase activity, finally resulting in an IMR susceptibility phenotype for KPC-14. Expansion of the substrate profile of KPC-14 toward ceftazidime is associated with a trade-off for carbapenems, other penicillins, and cephalosporins, as well as a higher inhibition by clavulanic acid compared to KPC-2. This study provides a better understanding of how deletions in the 237-243 loop affect the effectiveness of novel DBO-combinations and supports the hypothesis that these mutations result in CZA resistance by other different biochemical mechanisms than mutations in the Ω-loop.
β-内酰胺-二氮杂双环辛烷抑制剂（DBOs）组合，如头孢他啶-阿维巴坦（CZA）和亚胺培南-瑞来巴坦（IMR），已显示出对产KPC-2菌株的治疗效果。然而，已鉴定出对CZA耐药的菌株，这些菌株通常与KPC三个不同环中的取代和/或插入/缺失有关：（i）Ω环区域（氨基酸164 - 179），（ii）237 - 243环；以及（iii）266 - 275环。本研究调查了KPC-14中存在的双缺失ΔG242 - T243的影响。我们的结果表明，CZA对KPC-14有效性较低的原因，既可以通过头孢他啶水解增加来解释，也可以通过阿维巴坦的较低亲和力和酰化率来解释。相比之下，IMR组合能有效恢复对产KPC-14克隆的敏感性。尽管我们也观察到KPC-14中瑞来巴坦的亲和力和酰化率较低，但这种亲和力的降低伴随着碳青霉烯酶活性的丧失，最终导致KPC-14对IMR敏感的表型。KPC-14对头孢他啶底物谱的扩展与对碳青霉烯类、其他青霉素类和头孢菌素类的权衡有关，并且与克拉维酸相比，KPC-14对克拉维酸的抑制作用更强。本研究更好地理解了237 - 243环中的缺失如何影响新型DBO组合的有效性，并支持了这样的假设，即这些突变通过与Ω环突变不同的生化机制导致CZA耐药。
