Research Service, Louis Stokes Cleveland Department of Veterans Affairs, Cleveland, Ohio, USA.
Department of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.
Antimicrob Agents Chemother. 2019 Mar 27;63(4). doi: 10.1128/AAC.02315-18. Print 2019 Apr.
spp. are opportunistic human pathogens that infect persons with cystic fibrosis and the immunocompromised. spp. express class A and C β-lactamases, which are transcriptionally regulated by PenR through linkage to cell wall metabolism and β-lactam exposure. The potency of temocillin, a 6-methoxy-β-lactam, was tested against a panel of multidrug-resistant (MDR) spp. In addition, the mechanistic basis of temocillin activity was assessed and compared to that of ticarcillin. Susceptibility testing with temocillin and ticarcillin was conducted, as was biochemical analysis of the PenA1 class A β-lactamase and AmpC1 class C β-lactamase. Molecular dynamics simulations (MDS) were performed using PenA1 with temocillin and ticarcillin. The majority (86.7%) of 150 MDR strains were susceptible to temocillin, while only 4% of the strains were susceptible to ticarcillin. Neither temocillin nor ticarcillin induced expression. Ticarcillin was hydrolyzed by PenA1 (/ = 1.7 ± 0.2 μM s), while temocillin was slow to form a favorable complex (apparent [] = ∼2 mM). Ticarcillin and temocillin were both potent inhibitors of AmpC1, with values of 4.9 ± 1.0 μM and 4.3 ± 0.4 μM, respectively. MDS of PenA revealed that ticarcillin is in an advantageous position for acylation and deacylation. Conversely, with temocillin, active-site residues K73 and S130 are rotated and the catalytic water molecule is displaced, thereby slowing acylation and allowing the 6-methoxy of temocillin to block deacylation. Temocillin is a β-lactam with potent activity against spp., as it does not induce expression and is poorly hydrolyzed by endogenous β-lactamases.
spp. 是机会性人类病原体，感染囊性纤维化和免疫功能低下的人群。 spp. 表达 A 类和 C 类β-内酰胺酶，这些酶通过与细胞壁代谢和β-内酰胺暴露的连接，由 PenR 转录调控。6-甲氧基-β-内酰胺替莫西林对一组多药耐药（MDR） spp. 的效力进行了测试。此外，还评估并比较了替莫西林和替卡西林的作用机制。进行了替莫西林和替卡西林的药敏试验以及 PenA1 类 A 型β-内酰胺酶和 AmpC1 类 C 型β-内酰胺酶的生化分析。使用 PenA1 进行了分子动力学模拟（MDS），并与替莫西林和替卡西林一起进行了分子动力学模拟。150 株 MDR 株中的大多数（86.7%）对替莫西林敏感，而只有 4%的菌株对替卡西林敏感。替莫西林和替卡西林均未诱导 表达。PenA1 水解替卡西林（/ = 1.7±0.2μM s），而替莫西林形成有利复合物的速度较慢（表观 [] = ∼2 mM）。替卡西林和替莫西林都是 AmpC1 的有效抑制剂， 值分别为 4.9±1.0 μM 和 4.3±0.4 μM。PenA 的 MDS 显示，替卡西林在酰化和脱酰化方面处于有利地位。相反，对于替莫西林，活性位点残基 K73 和 S130 旋转，催化水分子被取代，从而减缓酰化作用，并允许替莫西林的 6-甲氧基阻止脱酰化。替莫西林是一种对 spp. 具有强大活性的β-内酰胺，因为它不会诱导 表达，并且被内源性β-内酰胺酶水解的速度较慢。
