Structural Basis of Reduced Susceptibility to Ceftazidime-Avibactam and Cefiderocol in Enterobacter cloacae Due to AmpC R2 Loop Deletion

• Published in: Antimicrobial agents and chemotherapy 2020-06, Vol.64 (7)
• Main Authors: Kawai, Akito, McElheny, Christi L, Iovleva, Alina, Kline, Ellen G, Sluis-Cremer, Nicolas, Shields, Ryan K, Doi, Yohei
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Azabicyclo Compounds - pharmacology; beta-Lactamases - genetics; Cefiderocol; Ceftazidime - pharmacology; Cephalosporins; Drug Combinations; Enterobacter cloacae - genetics; Mechanisms of Resistance; Microbial Sensitivity Tests
• ISSN: 0066-4804; 1098-6596
• DOI: 10.1128/AAC.00198-20

Ceftazidime-avibactam and cefiderocol are two of the latest generation β-lactam agents that possess expanded activity against highly drug-resistant bacteria, including carbapenem-resistant Here, we show that structural changes in AmpC β-lactamases can confer reduced susceptibility to both agents. A multidrug-resistant clinical strain (Ent385) was found to be resistant to ceftazidime-avibactam and cefiderocol without prior exposure to either agent. The AmpC β-lactamase of Ent385 (AmpC ) contained an alanine-proline deletion at positions 294 and 295 (A294_P295del) in the R2 loop. AmpC conferred reduced susceptibility to ceftazidime-avibactam and cefiderocol when cloned into TOP10. Purified AmpC showed increased hydrolysis of ceftazidime and cefiderocol compared to AmpC , in which the deletion was reverted. Comparisons of crystal structures of AmpC and AmpC , the canonical AmpC of complex, revealed that the two-residue deletion in AmpC 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 to confer reduced susceptibility to both ceftazidime-avibactam and cefiderocol requires close monitoring.