Qpex BioPharma, Inc., San Diego, California, USA.
Qpex BioPharma, Inc., San Diego, California, USA
Antimicrob Agents Chemother. 2020 Mar 24;64(4). doi: 10.1128/AAC.01936-19.
Resistance to ceftazidime-avibactam due to mutations in KPC genes has been reported both and in clinical settings. The most frequently reported mutation leads to the amino acid substitution D179Y in the Ω loop of the enzyme. Bacterial cells that carry mutant KPC acquire a higher level of ceftazidime resistance, become more sensitive to other cephalosporins, and almost completely lose resistance to carbapenems. In this study, we demonstrated that two substitutions in KPC-2, D179Y and L169P, reduce the ability of avibactam to enhance the activity of ceftazidime, cefepime, or piperacillin against isogenic efflux-deficient strains of , 8- to 32-fold and 4- to 16-fold for the D179Y and L169P variants, respectively, depending on the antibiotic. In contrast, the potency of vaborbactam, the structurally unrelated β-lactamase inhibitor that was recently approved by the FDA in combination with meropenem, is reduced no more than 2-fold. Experiments with purified enzymes demonstrate that the D179Y substitution causes an ∼20-fold increase in the 50% inhibitory concentration (IC) for inhibition of ceftazidime hydrolysis by avibactam, versus 2-fold for vaborbactam, and that the L169P substitution has an ∼4.5-fold-stronger effect on the affinity for avibactam than for vaborbactam. In addition, the D179Y and L169P variants hydrolyze ceftazidime with 10-fold and 4-fold-higher efficiencies, respectively, than that of wild-type KPC-2. Thus, microbiological and biochemical experiments implicate both decreased ability of avibactam to interact with KPC-2 variants and an increase in the efficiency of ceftazidime hydrolysis in resistance to ceftazidime-avibactam. These substitutions have a considerably lesser effect on interactions with vaborbactam, making the meropenem-vaborbactam combination a valuable agent in managing infections due to KPC-producing carbapenem-resistant .
由于 KPC 基因的突变导致对头孢他啶-阿维巴坦的耐药性已在临床和临床前研究中得到报道。最常报道的突变导致酶的 Ω环中的氨基酸取代 D179Y。携带突变 KPC 的细菌细胞获得更高水平的头孢他啶耐药性，对其他头孢菌素更敏感，几乎完全失去对碳青霉烯类的耐药性。在这项研究中，我们证明了 KPC-2 中的两个取代，D179Y 和 L169P，降低了阿维巴坦增强头孢他啶、头孢吡肟或哌拉西林对异源外排缺陷型的活性的能力，对于 D179Y 和 L169P 变体，分别为 8 到 32 倍和 4 到 16 倍，这取决于抗生素。相比之下，结构上不相关的β-内酰胺酶抑制剂瓦博巴坦的效力降低不超过 2 倍，瓦博巴坦最近被 FDA 批准与美罗培南联合使用。用纯化酶进行的实验表明，D179Y 取代导致阿维巴坦抑制头孢他啶水解的 50%抑制浓度（IC）增加约 20 倍，而对瓦博巴坦则增加 2 倍，而 L169P 取代对阿维巴坦的亲和力比对瓦博巴坦的亲和力强约 4.5 倍。此外，D179Y 和 L169P 变体水解头孢他啶的效率分别比野生型 KPC-2 高 10 倍和 4 倍。因此，微生物学和生物化学实验表明，阿维巴坦与 KPC-2 变体相互作用的能力降低以及头孢他啶水解效率的提高都导致了对头孢他啶-阿维巴坦的耐药性。这些取代对与瓦博巴坦的相互作用的影响要小得多，使得美罗培南-瓦博巴坦联合成为治疗产 KPC 碳青霉烯类耐药菌引起的感染的有价值的药物。
