Institut für Medizinische Mikrobiologie, Virologie und Hygiene, Universitätsklinikum Hamburg-Eppendorf, Martinistraße 52, 20246 Hamburg, Germany.
Laboratory for Structural Biology of Infection and Inflammation, c/o DESY, Notkestraße 85, Build. 22a, 22603 Hamburg, Germany.
J Antimicrob Chemother. 2017 Sep 1;72(9):2483-2488. doi: 10.1093/jac/dkx179.
Avibactam is a novel broad-range β-lactamase inhibitor active against Ambler class A (including ESBL and KPC) and some Ambler class C and D (e.g. OXA-48) enzymes. We here report on the emergence of ceftazidime/avibactam resistance in clinical, multiresistant, OXA-48 and CTX-M-14-producing Klebsiella pneumoniae isolate DT12 during ceftazidime/avibactam treatment.
Comparative whole-genome sequence analysis identified two SNPs in the CTX-M-14-encoding gene leading to two amino acid changes (P170S and T264I). Compared with WT CTX-M-14, expression of the CTX-M-14Δ170Δ264 isoform in Escherichia coli led to a >64- and 16-fold increase in ceftazidime and ceftazidime/avibactam MICs, respectively, functionally linking the observed SNPs and elevated MICs. The mutated CTX-M-14 isoform exhibited augmented ceftazidime hydrolytic activity, which was a reasonable cause for impaired susceptibility to avibactam inhibition. The P170S exchange in CTX-M-14 was found in association with elevated ceftazidime/avibactam MICs for independent K. pneumoniae isolates, but was not sufficient for full resistance. Apparently, additional CTX-M-independent mechanisms contribute to ceftazidime/avibactam resistance in K. pneumoniae DT12.
This study on the molecular basis of ceftazidime/avibactam resistance in clinical K. pneumoniae emerging in vivo underscores the need for continuous monitoring of ceftazidime/avibactam susceptibility during therapy. Despite sustained inhibition of OXA-48, rapid development of CTX-M-14 isoforms exhibiting augmented ceftazidime hydrolytic activity may limit the usefulness of ceftazidime/avibactam monotherapies in infections caused by isolates carrying blaCTX-M-14 and blaOXA-48.
阿维巴坦是一种新型广谱β-内酰胺酶抑制剂，对 Ambler 类 A（包括 ESBL 和 KPC）和一些 Ambler 类 C 和 D（如 OXA-48）酶具有活性。我们在此报告在使用头孢他啶/阿维巴坦治疗期间，临床、多耐药、产 OXA-48 和 CTX-M-14 的肺炎克雷伯菌分离株 DT12 中出现头孢他啶/阿维巴坦耐药。
比较全基因组序列分析确定了 CTX-M-14 编码基因中的两个 SNP，导致两个氨基酸变化（P170S 和 T264I）。与野生型 CTX-M-14 相比，CTX-M-14Δ170Δ264 同工型在大肠杆菌中的表达导致头孢他啶和头孢他啶/阿维巴坦 MIC 分别增加了>64 倍和 16 倍，功能上连接了观察到的 SNP 和升高的 MIC。突变的 CTX-M-14 同工型表现出增强的头孢他啶水解活性，这是对阿维巴坦抑制敏感性降低的合理原因。CTX-M-14 中的 P170S 交换与独立的肺炎克雷伯菌分离株中头孢他啶/阿维巴坦 MIC 升高有关，但不足以完全耐药。显然，CTX-M 独立的其他机制有助于肺炎克雷伯菌 DT12 中头孢他啶/阿维巴坦的耐药。
本研究阐明了临床肺炎克雷伯菌中头孢他啶/阿维巴坦耐药的分子基础，强调了在治疗过程中需要持续监测头孢他啶/阿维巴坦的敏感性。尽管持续抑制 OXA-48，但快速发展的 CTX-M-14 同工型表现出增强的头孢他啶水解活性可能会限制头孢他啶/阿维巴坦单药治疗在携带 blaCTX-M-14 和 blaOXA-48 的分离株引起的感染中的应用。
