The emergence of antibiotic-resistant strains of Mycobacterium tuberculosis and the decelerating development of new and effective antibiotics has impaired the treatment of tuberculosis (TB). Efflux pump inhibitors (EPIs) have the potential to improve the efficacy of existing anti-TB drugs although with toxicity limitations. Peptide nucleic acids (PNAs), oligonucleotide mimics, by virtue of their high nucleic acid binding specificity have the capability to overcome this drawback. We, therefore, investigated the efflux pump inhibitory properties of a PNA designed against an efflux pump of Mycobacterium smegmatis. LfrA, an efflux pump found in M. smegmatis, is majorly involved in conferring innate drug resistance to this strain and, therefore, was selected as a target for gene silencing via PNA. qRT-PCR and EtBr assays confirmed the EPI activity of the anti-lfrA PNA. On testing the effect of the anti-lfrA PNA on the bactericidal activity of a fluoroquinolone, norfloxacin, we observed that 5 μM of anti-lfrA PNA in combination with norfloxacin led to an enhanced killing of up to 2.5 log-fold against wild-type and a lab-generated multidrug resistant strain, exemplifying its potential in countering resistance. Improved efficacy was also observed against intra-macrophage mycobacteria, where the drug-PNA combination enhanced bacterial clearance by 1.3 log-fold. Further, no toxicity was observed with PNA concentrations up to 4 times higher than the efficacious anti-lfrA PNA concentration. Thus, PNA, as an adjuvant, presents a novel and viable approach to rejuvenate anti-TB therapeutics.

结核分枝杆菌的抗生素耐药菌株的出现以及新的有效抗生素的发展日新月异，已经损害了结核病的治疗。外排泵抑制剂（EPI）具有改善现有抗结核药物疗效的潜力，尽管具有毒性限制。肽核酸（PNA），寡核苷酸模拟物，由于其高核酸结合特异性而具有克服这一缺点的能力。因此，我们研究了针对耻垢分枝杆菌的外排泵设计的PNA的外排泵抑制特性。LfrA，耻垢分枝杆菌中发现的外排泵，主要参与赋予该菌株固有的抗药性，因此被选为通过PNA基因沉默的靶标。qRT-PCR和EtBr分析证实了抗lfrA PNA的EPI活性。在测试抗lfrA PNA对氟喹诺酮，诺氟沙星的杀菌活性的影响时，我们观察到5μM的抗lfrAPNA与诺氟沙星联用可导致针对野生型和实验室产生的耐多药菌株的杀伤力提高多达2.5个对数倍，体现了其抗药性的潜力。还观察到对抗巨噬细胞内分枝杆菌的功效提高，其中药物-PNA组合将细菌清除率提高了1.3个对数倍。此外，在PNA浓度比有效的抗lfrA PNA浓度高4倍的情况下，未观察到毒性。因此，作为佐剂的PNA提出了一种新颖且可行的方法来复兴抗结核疗法。