Krishnamurthy Malathy, Lemmon Margaret M, Falcinelli Evan M, Sandy Reuel A, Dootz Jennifer N, Mott Tiffany M, Rajamani Sathish, Schaecher Kurt E, Duplantier Allen J, Panchal Rekha G
Department of Target Discovery and Experimental Microbiology, Division of Molecular and Translational Sciences, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD, USA.
General Dynamics Information Technology, Frederick, MD, USA.
Infect Drug Resist. 2019 May 27;12:1393-1405. doi: 10.2147/IDR.S196874. eCollection 2019.
The rapid emergence of multidrug-resistant (MDR) bacteria and the lack of new therapies to eliminate them poses a major threat to global health. With the alarming rise in antimicrobial resistance (AMR), focus has now shifted to the use of the polymyxin class of antibiotics as the last line of defense for treatment of Gram-negative infections. Unfortunately, the growing resistance of bacteria against polymyxins is threatening the treatment of MDR infections, necessitating the need for novel strategies. The objective of this study was to determine if combination of polymyxin (polymyxin B or colistin) with a nonantibiotic small molecule AR-12, a celecoxib derivative that is devoid of cyclooxygenase 2 (COX-2) inhibitory activities, can be an effective strategy against polymyxin-resistant MDR bacteria. Growth inhibition studies, time-kill assays and permeability assays were conducted to investigate the effect of AR-12 on the antibacterial activity of polymyxins. Growth studies were performed on a panel of polymyxin-resistant MDR strains using the combination of AR-12 with either colistin or polymyxin B. The combination treatment had no effect on strains that have inherent polymyxin resistance; however, AR-12 was effective in lowering the minimal inhibitory concentration (MIC) of polymyxins by 4-60-fold in several strains that had acquired polymyxin resistance. Time-kill assays using the combination of AR-12 and colistin with select MDR strains suggest rapid killing and bactericidal activity, while the permeability assays using fluorescently labeled dansylated polymyxin and 1-N-phenylnaphthylamine (NPN) in these MDR strains suggest that AR-12 can potentiate the antibacterial activity of polymyxins by possibly altering the bacterial outer membrane via modification of lipopolysaccharide and thereby improving the uptake of polymyxins. Our studies indicate that the combination of AR-12 and polymyxin is effective in targeting select Gram-negative bacteria that have acquired polymyxin resistance. Further understanding of the mechanism of action of AR-12 will provide new avenues for developing narrow-spectrum antibacterials to target select Gram-negative MDR bacteria. Importantly, our studies show that the use of nonantibiotic small molecules in combination with polymyxins is an attractive strategy to counter the growing resistance of bacteria to polymyxins.
多重耐药（MDR）细菌的迅速出现以及消除这些细菌的新疗法的缺乏对全球健康构成了重大威胁。随着抗菌药物耐药性（AMR）惊人地上升，现在的重点已转向使用多粘菌素类抗生素作为治疗革兰氏阴性菌感染的最后一道防线。不幸的是，细菌对多粘菌素的耐药性不断增加，正威胁着多重耐药感染的治疗，因此需要新的策略。本研究的目的是确定多粘菌素（多粘菌素B或黏菌素）与非抗生素小分子AR-12（一种不含环氧合酶2（COX-2）抑制活性的塞来昔布衍生物）联合使用是否能成为对抗耐多粘菌素的多重耐药细菌的有效策略。进行了生长抑制研究、时间杀菌试验和通透性试验，以研究AR-12对多粘菌素抗菌活性的影响。使用AR-12与黏菌素或多粘菌素B的组合，对一组耐多粘菌素的多重耐药菌株进行了生长研究。联合治疗对具有固有多粘菌素耐药性的菌株没有效果；然而，在几种获得多粘菌素耐药性的菌株中，AR-12有效地将多粘菌素的最低抑菌浓度（MIC）降低了4至60倍。使用AR-12和黏菌素与选定的多重耐药菌株进行的时间杀菌试验表明有快速杀菌作用和杀菌活性，而在这些多重耐药菌株中使用荧光标记的丹磺酰化多粘菌素和1-N-苯基萘胺（NPN）进行的通透性试验表明，AR-12可能通过修饰脂多糖改变细菌外膜，从而提高多粘菌素的摄取，进而增强多粘菌素的抗菌活性。我们的研究表明，AR-12和多粘菌素联合使用对选定的已获得多粘菌素耐药性的革兰氏阴性菌有效。进一步了解AR-12的作用机制将为开发针对选定的革兰氏阴性多重耐药细菌的窄谱抗菌药物提供新途径。重要的是，我们的研究表明，使用非抗生素小分子与多粘菌素联合是应对细菌对多粘菌素耐药性不断增加的一种有吸引力的策略。
