Institute for Medical Microbiology and Infection Control, Hospital of the Goethe University, Frankfurt am Main, Germany.
Faculty of Biological Sciences of the Goethe University, Frankfurt am Main, Germany.
J Antimicrob Chemother. 2021 Feb 11;76(3):626-634. doi: 10.1093/jac/dkaa488.
This study analysed the novel carbapenem-hydrolysing class D β-lactamase OXA-822 identified in the clinical Acinetobacter calcoaceticus isolate AC_2117.
WGS was employed for identification of β-lactamases. Micro-broth dilution was used for evaluation of antibiotic susceptibility of AC_2117 and transformants containing blaOXA-822. After heterologous purification of OXA-822, OXA-359 and OXA-213, enzyme kinetics were determined using spectrometry. The effect of OXA-822 upon meropenem treatment was analysed in the Galleria mellonella in vivo infection model.
OXA-822 is a member of the intrinsic OXA-213-like family found in A. calcoaceticus and Acinetobacter pittii. Amino acid sequence similarity to the nearest related OXA-359 was 97%. Production of OXA-822, OXA-359 and OXA-213 in Acinetobacter baumannii ATCC® 19606T resulted in elevated MICs for carbapenems (up to 16-fold). Penicillinase activity of the purified OXA-822 revealed high KM values, in the millimolar range, combined with high turnover numbers. OXA-822 showed the highest affinity to carbapenems, but affinity to imipenem was ∼10-fold lower compared with other carbapenems. Molecular modelling revealed that imipenem does not interact with a negatively charged side chain of OXA-822, as doripenem does, leading to the lower affinity. Presence of OXA-822 decreased survival of infected Galleria mellonella larvae after treatment with meropenem. Only 52.7% ± 7.7% of the larvae survived after 24 h compared with 90.9% ± 3.7% survival in the control group.
The novel OXA-822 from a clinical A. calcoaceticus isolate displayed penicillinase and carbapenemase activity in vitro, elevated MICs in different species and decreased carbapenem susceptibility in A. baumannii in vivo.
本研究分析了临床分离的鲍曼不动杆菌 AC_2117 中发现的新型碳青霉烯水解类 Dβ-内酰胺酶 OXA-822。
采用 WGS 鉴定β-内酰胺酶。采用微量肉汤稀释法评估 AC_2117 及其含 blaOXA-822 转化子的抗生素敏感性。异源纯化 OXA-822、OXA-359 和 OXA-213 后，采用光谱法测定酶动力学。在体内感染模型中分析 OXA-822 对美罗培南治疗的影响。
OXA-822 是一种在鲍曼不动杆菌和醋酸钙不动杆菌中发现的固有 OXA-213 样家族的成员。与最近的 OXA-359 氨基酸序列相似性为 97%。在鲍曼不动杆菌 ATCC®19606T 中产生 OXA-822、OXA-359 和 OXA-213 导致碳青霉烯类药物 MIC 升高（高达 16 倍）。纯化的 OXA-822 的青霉素酶活性显示出高 KM 值，在毫摩尔范围内，结合高 turnover 数。OXA-822 对碳青霉烯类药物表现出最高的亲和力，但与其他碳青霉烯类药物相比，对亚胺培南的亲和力低 10 倍。分子建模显示，亚胺培南与 OXA-822 的带负电荷侧链没有相互作用，而多尼培南则有相互作用，导致亲和力较低。OXA-822 的存在降低了感染的大蜡螟幼虫在用美罗培南治疗后的存活率。与对照组 90.9%±3.7%的存活率相比，24 小时后仅有 52.7%±7.7%的幼虫存活。
来自临床分离的鲍曼不动杆菌的新型 OXA-822 在体外显示出青霉素酶和碳青霉烯酶活性，在不同种属中 MIC 升高，在体内降低了鲍曼不动杆菌对碳青霉烯类药物的敏感性。
