Department of Medicine, Farncombe Family Digestive Health Research Institute, Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada
Department of Medicine, Farncombe Family Digestive Health Research Institute, Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada.
J Bacteriol. 2018 Aug 24;200(18). doi: 10.1128/JB.00156-18. Print 2018 Sep 15.
Antibiotic resistance is a threat to our modern society, and new strategies leading to the identification of new molecules or targets to combat multidrug-resistant pathogens are needed. Species of the genus , including the complex (Bcc), , and , can be highly pathogenic and are intrinsically resistant to multiple classes of antibiotics. Bcc species are nonetheless sensitive to extracellular products released by in interspecies competition. We screened for transposon mutants with increased sensitivity to spent medium and identified multiple mutants in genes sharing homology with the Mla pathway. Insertional mutants in representative genes of the Bcc Mla pathway had a compromised cell membrane and were more sensitive to various extracellular stresses, including antibiotics and human serum. More precisely, mutants in the Bcc species and were more susceptible to Gram-positive antibiotics (i.e., macrolides and rifampin), fluoroquinolones, tetracyclines, and chloramphenicol. Genetic complementation of insertional mutants restored cell permeability and resistance to Gram-positive antibiotics. Importantly, Bcc mutants were not universally weaker strains since their susceptibilities to other classes of antibiotics were unaffected. Although cell permeability of homologous mutants in or was also impaired, they were not more sensitive to Gram-positive antibiotics or other antimicrobials as was observed in Bcc mutants. Together, the data suggest that the Mla pathway in may play a different biological role, which could potentially represent a -specific drug target in combination therapy with antibiotic adjuvants. The outer membrane of Gram-negative bacteria acts as an effective barrier against toxic compounds, and therefore compromising this structure could increase sensitivity to currently available antibiotics. In this study, we show that the Mla pathway, a system involved in maintaining the integrity of the outer membrane, is genetically and functionally different in complex species compared to that in other proteobacteria. Mutants in genes of or were sensitive to Gram-positive antibiotics, while this effect was not observed in or The Mla pathway in species may represent an ideal genus-specific target to address their intrinsic antimicrobial resistances.
抗生素耐药性是我们现代社会面临的威胁，因此需要新的策略来鉴定新的分子或靶标，以对抗多药耐药病原体。属中的物种，包括复杂的（Bcc），，和，可以是高度致病性的，并且对多种类别的抗生素固有耐药。然而，Bcc 物种对物种间竞争中释放的细胞外产物敏感。我们筛选了对 细胞外产物敏感的转座子突变体，并在与 Mla 途径同源的基因中鉴定出多个突变体。Bcc Mla 途径的代表性基因的插入突变体的细胞膜受损，对各种细胞外应激（包括抗生素和人血清）更敏感。更准确地说，Bcc 物种中的突变体对革兰氏阳性抗生素（即大环内酯类和利福平）、氟喹诺酮类、四环素类和氯霉素更敏感。插入突变体的基因互补恢复了细胞通透性和对革兰氏阳性抗生素的耐药性。重要的是，Bcc 突变体不是普遍较弱的菌株，因为它们对其他类别的抗生素的敏感性不受影响。尽管 或 中的同源突变体的细胞通透性也受损，但与 Bcc 突变体观察到的情况不同，它们对革兰氏阳性抗生素或其他抗菌药物的敏感性没有增加。总之，数据表明 Mla 途径在 中可能发挥不同的生物学作用，这可能代表与抗生素佐剂联合治疗中的一种 -特异性药物靶标。革兰氏阴性细菌的外膜作为一种有效的屏障，防止有毒化合物进入，因此破坏这种结构可以增加对现有抗生素的敏感性。在这项研究中，我们表明，参与维持外膜完整性的 Mla 途径在 复合体物种中的遗传和功能与其他变形菌不同。或 基因的突变体对革兰氏阳性抗生素敏感，而在 或 中则没有观察到这种作用。属中的 Mla 途径可能代表一个理想的属特异性靶标，以解决其内在的抗菌耐药性。
