Structural Basis of Reduced Susceptibility to Ceftazidime-Avibactam and Cefiderocol in Enterobacter cloacae Due to AmpC R2 Loop Deletion
Structural Basis of Reduced Susceptibility to Ceftazidime-Avibactam and Cefiderocol in Enterobacter cloacae Due to AmpC R2 Loop Deletion
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DOI：
10.1128/aac.00198-20
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发表时间：
2020-07-01
影响因子：
4.9
通讯作者：
Doi, Yohei
中科院分区：
文献类型：
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作者：
Kawai, Akito;McElheny, Christi L.;Doi, Yohei
头孢他啶-阿维巴坦和头孢地罗可是两种最新一代β-内酰胺类药物，对高度耐药细菌（包括碳青霉烯类耐药肠球菌）具有扩展活性。在这里，我们表明，AmpC β-内酰胺酶的结构变化可以降低对这两种药物的敏感性。发现一种多重耐药阴沟肠杆菌临床菌株（Ent 385）对头孢他啶-阿维巴坦和头孢地罗可耐药，既往未暴露于任何一种药物。Ent 385的AmpC β-内酰胺酶（AmpC（Ent 385））在R2环中的位置294和295（A294_P295del）处含有丙氨酸-脯氨酸缺失。AmpC（Ent 385）在克隆至大肠埃希菌TOP 10中时，降低了对头孢他啶-阿维巴坦和头孢地考的敏感性。纯化的AmpC（Ent 385）显示，与AmpC（Ent 385 Rev）相比，头孢他啶和头孢地罗醇的水解增加，其中缺失被恢复。对大肠杆菌AmpC（Ent 385）和AmpC（P99）的晶体结构进行了比较。cloxacol复合物的研究表明，AmpC（Ent 385）中的两个残基缺失引起H-9和H-10螺旋以及R2环的剧烈结构变化，这是头孢他啶和头孢地罗醇水解增加的原因。需要密切监测ampC中单个突变降低头孢他啶-阿维巴坦和头孢地罗可敏感性的可能性。
Ceftazidime-avibactam and cefiderocol are two of the latest generation beta-lactam agents that possess expanded activity against highly drug-resistant bacteria, including carbapenem-resistant Enterobacterales. Here, we show that structural changes in AmpC beta-lactamases can confer reduced susceptibility to both agents. A multidrug-resistant Enterobacter cloacae clinical strain (Ent385) was found to be resistant to ceftazidime-avibactam and cefiderocol without prior exposure to either agent. The AmpC beta-lactamase of Ent385 (AmpC(Ent385)) contained an alanine-proline deletion at positions 294 and 295 (A294_P295del) in the R2 loop. AmpC(Ent385) conferred reduced susceptibility to ceftazidime-avibactam and cefiderocol when cloned into Escherichia coli TOP10. Purified AmpC(Ent385) showed increased hydrolysis of ceftazidime and cefiderocol compared to AmpC(Ent385Rev), in which the deletion was reverted. Comparisons of crystal structures of AmpC(Ent385) and AmpC(P99), the canonical AmpC of E. cloacae complex, revealed that the two-residue deletion in AmpC(Ent385) induced drastic structural changes of the H-9 and H-10 helices and the R2 loop, which accounted for the increased hydrolysis of ceftazidime and cefiderocol. The potential for a single mutation in ampC to confer reduced susceptibility to both ceftazidime-avibactam and cefiderocol requires close monitoring.