Pi Hongfei, Venter Henrietta, Russell Cecilia C, Young Kelly A, McCluskey Adam, Page Stephen W, Ogunniyi Abiodun D, Trott Darren J
Australian Centre for Antimicrobial Resistance Ecology, School of Animal and Veterinary Sciences, Roseworthy Campus, University of Adelaide, Roseworthy, SA 5371, Australia.
Health and Biomedical Innovation, Clinical and Health Sciences, University of South Australia, Adelaide, SA 5000, Australia.
Antibiotics (Basel). 2022 Sep 23;11(10):1301. doi: 10.3390/antibiotics11101301.
Multidrug-resistant (MDR) Gram-negative pathogens, especially Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli and Enterobacter spp., are recognized by the World Health Organization as the most critical priority pathogens in urgent need of drug development. In this study, the in vitro antimicrobial activity of robenidine analogues NCL259 and NCL265 was tested against key human and animal Gram-negative clinical isolates and reference strains. NCL259 and NCL265 demonstrated moderate antimicrobial activity against these Gram-negative priority pathogens with NCL265 consistently more active, achieving lower minimum inhibitory concentrations (MICs) in the range of 2−16 µg/mL. When used in combination with sub-inhibitory concentrations of polymyxin B to permeabilize the outer membrane, NCL259 and NCL265 elicited a synergistic or additive activity against the reference strains tested, reducing the MIC of NCL259 by 8- to 256- fold and the MIC of NCL265 by 4- to 256- fold. A small minority of Klebsiella spp. isolates (three) were resistant to both NCL259 and NCL265 with MICs > 256 µg/mL. This resistance was completely reversed in the presence of the efflux pump inhibitor phenylalanine-arginine-beta-naphthylamide (PAβN) to yield MIC values of 8−16 µg/mL and 2−4 µg/mL for NCL259 and NCL256, respectively. When NCL259 and NCL265 were tested against wild-type E. coli isolate BW 25113 and its isogenic multidrug efflux pump subunit AcrB deletion mutant (∆AcrB), the MIC of both compounds against the mutant ∆AcrB isolate was reduced 16-fold compared to the wild-type parent, indicating a significant role for the AcrAB-TolC efflux pump from Enterobacterales in imparting resistance to these robenidine analogues. In vitro cytotoxicity testing revealed that NCL259 and NCL265 had much higher levels of toxicity to a range of human cell lines compared to the parent robenidine, thus precluding their further development as novel antibiotics against Gram-negative pathogens.
多重耐药（MDR）革兰氏阴性病原体，尤其是鲍曼不动杆菌、铜绿假单胞菌、大肠杆菌和肠杆菌属，被世界卫生组织认定为迫切需要开发新药物的最关键优先病原体。在本研究中，测试了罗苯尼丁类似物NCL259和NCL265对关键的人类和动物革兰氏阴性临床分离株及参考菌株的体外抗菌活性。NCL259和NCL265对这些革兰氏阴性优先病原体表现出中等抗菌活性，其中NCL265活性更强，最低抑菌浓度（MIC）在2−16 µg/mL范围内。当与亚抑菌浓度的多粘菌素B联合使用以通透外膜时，NCL259和NCL265对测试的参考菌株产生协同或相加活性，使NCL259的MIC降低8至256倍，NCL265的MIC降低4至256倍。少数克雷伯菌属分离株（三株）对NCL259和NCL265均耐药，MIC>256 µg/mL。在存在外排泵抑制剂苯丙氨酸-精氨酸-β-萘酰胺（PAβN）的情况下，这种耐药性完全逆转，NCL259和NCL256的MIC值分别为8−16 µg/mL和2−4 µg/mL。当对野生型大肠杆菌分离株BW 25113及其同基因多药外排泵亚基AcrB缺失突变体（∆AcrB）测试NCL259和NCL265时，与野生型亲本相比，这两种化合物对突变体∆AcrB分离株的MIC均降低了16倍，表明肠杆菌科的AcrAB-TolC外排泵在赋予对这些罗苯尼丁类似物的耐药性方面发挥了重要作用。体外细胞毒性测试表明，与亲本罗苯尼丁相比，NCL259和NCL265对一系列人类细胞系具有更高水平的毒性，因此排除了它们作为抗革兰氏阴性病原体新型抗生素进一步开发的可能性。
