Centre National de Référence de la Résistance aux Antibiotiques, Centre Hospitalier Universitaire de Besançon, Besançon, France.
Institut des Sciences Analytiques, UMR CNRS 5280, Université Claude Bernard Lyon 1, Villeurbanne, France.
Antimicrob Agents Chemother. 2021 Jan 20;65(2). doi: 10.1128/AAC.01117-20.
Resistance mechanisms of to ceftolozane/tazobactam (C/T) were assessed on a collection of 420 nonredundant strains nonsusceptible to ceftazidime (MIC > 8 μg/ml) and/or imipenem (>4 μg/ml), collected by 36 French hospital laboratories over a one-month period (the GERPA study). Rates of C/T resistance (MIC > 4/4 μg/ml) were equal to 10% in this population (42/420 strains), and 23.2% (26/112) among the isolates resistant to both ceftazidime and imipenem. A first group of 21 strains (50%) was found to harbor various extended-spectrum β-lactamases (1 OXA-14; 2 OXA-19; 1 OXA-35; 1 GES-9; and 3 PER-1), carbapenemases (2 GES-5; 1 IMP-8; and 8 VIM-2), or both (1 VIM-2/OXA-35 and 1 VIM-4/SHV-2a). All the strains of this group belonged to widely distributed epidemic clones (ST111, ST175, CC235, ST244, ST348, and ST654), and were highly resistant to almost all the antibiotics tested except colistin. A second group was composed of 16 (38%) isolates moderately resistant to C/T (MICs from 8/4 to 16/4 μg/ml), of which 7 were related to international clones (ST111, ST253, CC274, ST352, and ST386). As demonstrated by targeted mass spectrometry, cloxacillin-based inhibition tests, and gene deletion experiments, this resistance phenotype was correlated with an extremely high production of cephalosporinase PDC. In part accounting for this strong PDC upregulation, genomic analyses revealed the presence of mutations in the regulator AmpR (D135N/G in 6 strains) and enzymes of the peptidoglycan recycling pathway, such as AmpD, PBP4, and Mpl (9 strains). Finally, all of the 5 (12%) remaining C/T-resistant strains (group 3) appeared to encode PDC variants with mutations known to improve the hydrolytic activity of the β-lactamase toward ceftazidime and C/T (F147L, ΔL223-Y226, E247K, and N373I). Collectively, our results highlight the importance of both intrinsic and transferable mechanisms in C/T-resistant Which mutational events lead some clinical strains to massively produce the natural cephalosporinase PDC remains incompletely understood.
在一项由 36 家法国医院实验室在一个月内收集的 420 株非冗余、对头孢他啶（MIC＞8μg/ml）和/或亚胺培南（＞4μg/ml）不敏感的非重复菌株中，评估对头孢洛扎/他唑巴坦（C/T）的耐药机制。在该人群中，C/T 耐药率（MIC＞4/4μg/ml）为 10%（42/420 株），而对头孢他啶和亚胺培南均耐药的分离株中耐药率为 23.2%（26/112）。第一组 21 株（50%）携带各种扩展谱β-内酰胺酶（1 株 OXA-14；2 株 OXA-19；1 株 OXA-35；1 株 GES-9；和 3 株 PER-1）、碳青霉烯酶（2 株 GES-5；1 株 IMP-8；和 8 株 VIM-2）或两者兼有（1 株 VIM-2/OXA-35 和 1 株 VIM-4/SHV-2a）。该组所有菌株均属于广泛传播的流行克隆（ST111、ST175、CC235、ST244、ST348 和 ST654），对几乎所有测试的抗生素均高度耐药，除黏菌素外。第二组由 16 株（38%）对 C/T 中度耐药的分离株（MIC 值为 8/4 至 16/4μg/ml）组成，其中 7 株与国际克隆株有关（ST111、ST253、CC274、ST352 和 ST386）。靶向质谱分析、氯唑西林基于抑制试验和基因缺失实验表明，这种耐药表型与头孢菌素酶 PDC 的超高表达有关。部分解释了这种强烈的 PDC 上调，基因组分析显示 AmpR 调节剂（6 株中的 D135N/G）和肽聚糖循环途径的酶，如 AmpD、PBP4 和 Mpl（9 株）的突变。最后，所有 5 株（12%）剩余的 C/T 耐药株（第 3 组）似乎编码了具有已知改善β-内酰胺酶对头孢他啶和 C/T 水解活性的突变的 PDC 变体（F147L、ΔL223-Y226、E247K 和 N373I）。总的来说，我们的研究结果强调了内在和可转移机制在 C/T 耐药中的重要性，目前尚不完全清楚哪些突变事件导致一些临床菌株大量产生天然头孢菌素酶 PDC。
