Reinseth Ingvild, Tønnesen Hanne H, Carlsen Harald, Diep Dzung B
Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway.
Section of Pharmaceutics and Social Pharmacy, Department of Pharmacy, University of Oslo, Blindern, Oslo, Norway.
Front Microbiol. 2021 Feb 17;12:649339. doi: 10.3389/fmicb.2021.649339. eCollection 2021.
The membrane-bound protease Eep is an important virulence factor in pathogenic enterococci. The protein is involved in stress response via the RIP pathway which is crucial for pathogenic enterococci to evade host immune attacks during infection. Eep serves also as a receptor for the bacteriocins enterocin K1 and enterocin EJ97. The bacteriocins kill and , respectively, and their antibiotic resistant derivatives including vancomycin resistant enterococci (VRE). This functional duality of Eep makes these two enterocins very promising as options in the prospective treatment of enterococcal infections because wildtype enterococcal cells (with an intact Eep) are sensitive to the bacteriocins while bacteriocin-resistant-mutants (without a functional Eep) become less virulent. As a first step to explore their therapeutic potential in the treatment of systemic enterococcal infections, we investigated the compatibility of the bacteriocins with human blood, and the phenotypic changes of -mutants toward different stress conditions. We found that the bacteriocins were compatible with blood, as they did not cause haemolysis and that the bacteriocins retained most of their antibacterial effect when incubated in blood. The bacteriocins were autoclavable which is a crucial criterium for the development of parenteral administration. -mutants, which became resistant to the bacteriocin were, as expected, less capable to withstand stress conditions such as exposure to lysozyme and desiccation. Further, their ability to chain, a trait implicated in niche adaptation as well as being necessary for genetic transfer via conjugation, was also severely affected. Together, these results indicate that the bacteriocins are promising for treatment of VRE infection.
膜结合蛋白酶Eep是致病性肠球菌中的一种重要毒力因子。该蛋白通过RIP途径参与应激反应，这对于致病性肠球菌在感染期间逃避宿主免疫攻击至关重要。Eep还作为细菌素肠球菌素K1和肠球菌素EJ97的受体。这些细菌素分别杀死粪肠球菌和屎肠球菌，以及它们的抗生素抗性衍生物，包括耐万古霉素肠球菌（VRE）。Eep的这种功能双重性使得这两种肠球菌素在肠球菌感染的前瞻性治疗中作为选择非常有前景，因为野生型肠球菌细胞（具有完整的Eep）对细菌素敏感，而细菌素抗性突变体（没有功能性Eep）的毒力则降低。作为探索它们在治疗全身性肠球菌感染中的治疗潜力的第一步，我们研究了细菌素与人类血液的相容性，以及粪肠球菌突变体对不同应激条件的表型变化。我们发现细菌素与血液相容，因为它们不会引起溶血，并且在血液中孵育时细菌素保留了大部分抗菌效果。细菌素可通过高压灭菌，这是肠胃外给药开发的关键标准。正如预期的那样，对细菌素产生抗性的粪肠球菌突变体在承受诸如暴露于溶菌酶和干燥等应激条件方面能力较弱。此外，它们的成链能力，这一与生态位适应以及通过接合进行基因转移所必需的特征，也受到严重影响。总之，这些结果表明细菌素在治疗VRE感染方面很有前景。
