Servicio de Microbiologia and Unidad de Investigacion, Hospital Universitario Son Espases, Instituto de Investigacion Sanitaria Illes Balears (IdISBa), Palma de Mallorca, Spain.
Wockhardt Research Centre, Aurangabad, India.
J Antimicrob Chemother. 2020 Jun 1;75(6):1474-1478. doi: 10.1093/jac/dkaa036.
The combination of cefepime and the novel β-lactam enhancer zidebactam (WCK 5222) is under development for the treatment of difficult-to-treat Gram-negative infections. Against MBL-producing pathogens, cefepime and zidebactam induce cell elongation and spheroplast formation, indicating PBP3 and PBP2 dysfunction, respectively, having a potent bactericidal effect as a combination. The objective of the present study was to determine the mechanistic basis of the bactericidal effect of cefepime/zidebactam on MBL-expressing pathogens.
Pseudomonal PBP-binding affinities of cefepime, zidebactam and imipenem were assessed at different timepoints and also in the presence of purified VIM-1 using a Bocillin FL competition assay. The antibacterial activity of cefepime/zidebactam against three VIM-expressing Pseudomonas aeruginosa isolates was assessed by time-kill and neutropenic mouse lung/thigh infection studies.
Amidst cefepime-hydrolysing concentrations of VIM-1, substantial cefepime binding to target PBPs was observed. High-affinity binding of zidebactam to PBP2 remained unaltered in the presence of VIM-1; however, MBL addition significantly affected imipenem PBP2 binding. Furthermore, the rate of cefepime binding to the primary target PBP3 was found to be higher compared with the imipenem PBP2 binding rate. Finally, complementary PBP inhibition by cefepime/zidebactam resulted in enhanced bactericidal activity in time-kill and neutropenic mouse lung/thigh infection studies against VIM-6-, VIM-10- and VIM-11-expressing P. aeruginosa, thus revealing the mechanistic basis of β-lactam enhancer action.
For the first time ever (to the best of our knowledge), this study demonstrates that in the presence of VIM-1 MBL, β-lactamase-labile cefepime and β-lactamase-stable zidebactam produce effective inhibition of respective target PBPs. For cefepime, this seems to be a result of a faster rate of PBP binding, which helps it overcome β-lactamase-mediated hydrolysis.
头孢吡肟与新型β-内酰胺增强剂齐他滨（WCK 5222）的联合应用正在开发中，用于治疗治疗困难的革兰氏阴性感染。针对产金属β-内酰胺酶（MBL）的病原体，头孢吡肟和齐他滨诱导细胞伸长和原生质体形成，分别表明 PBP3 和 PBP2 功能障碍，作为组合具有强大的杀菌作用。本研究的目的是确定头孢吡肟/齐他滨对产 MBL 病原体的杀菌作用的机制基础。
使用 Bocillin FL 竞争测定法，在不同时间点并在纯化的 VIM-1 的存在下评估头孢吡肟、齐他滨和亚胺培南与假单胞菌 PBP 的结合亲和力。通过时间杀伤和中性粒细胞减少的小鼠肺/大腿感染研究评估头孢吡肟/齐他滨对三种表达 VIM 的铜绿假单胞菌分离株的抗菌活性。
在 VIM-1 水解浓度下，观察到大量头孢吡肟与靶标 PBPs 结合。齐他滨与 PBP2 的高亲和力结合在 VIM-1 的存在下保持不变；然而，MBL 的添加显著影响了亚胺培南 PBP2 结合。此外，与亚胺培南 PBP2 结合率相比，发现头孢吡肟与主要靶标 PBP3 的结合率更高。最后，头孢吡肟/齐他滨的互补性 PBP 抑制导致在时间杀伤和中性粒细胞减少的小鼠肺/大腿感染研究中对表达 VIM-6、VIM-10 和 VIM-11 的铜绿假单胞菌的杀菌活性增强，从而揭示了β-内酰胺增强剂作用的机制基础。
这是首次（据我们所知）表明，在存在 VIM-1 MBL 的情况下，β-内酰胺酶不稳定的头孢吡肟和β-内酰胺酶稳定的齐他滨对各自的靶标 PBPs 产生有效抑制。对于头孢吡肟，这似乎是由于 PBP 结合更快的速度，这有助于它克服β-内酰胺酶介导的水解。
