Development of antimicrobial drugs targeting quorum sensing

针对细菌群体感应系统的抑制剂为治疗毒力和/或抗生素耐药感染提供了一种新的手段，并在体内或体外进行了群体感应研究。粪肠球菌毒力相关的明胶酶和丝氨酸蛋白酶的表达受FSR基因簇编码的群体感应系统的正调控。最近的研究表明，FSR系统更多地参与了生物膜的形成和其他酶的产生。在本研究中，我们从放线菌的次生代谢物中筛选针对FSR调节系统的群体感应抑制剂。粪肠球菌与各供试放线菌培养上清液共同培养，第一次和第二次筛选分别检测明胶酶和明胶酶生物合成激活信息素(GBAP)的产生。链霉菌培养上清液。齐Y33-1对明胶酶和GBAP的抑制作用最强，对粪肠球菌的生长没有抑制作用。从培养上清液中分离得到活性成分Y33-1。Y33-1在亚微摩尔浓度时抑制明胶酶和GBAP的产生，而在10微摩尔浓度以上时抑制粪肠球菌细胞的生长。Y33-1还抑制了粪肠球菌的明胶酶生成，表明Y33-1通过FSR系统抑制了GBAP的信号转导。目前正在进行Y33-1的结构分析和FSR抑制剂的进一步筛选，以及利用Y33-1进行化疗的可能性的研究。

Inhibitors targeting bacterial quorum sensing system offer a novel means of treating virulent and/or antibiotic resistant infections and quorum sensing researches in vivo or in vitro. The expression of two Enterococcus faecalis virulence-related proteases, gelatinase and serine protease, is positively regulated by a quorum sensing system encoded by fsr gene cluster. Recent studies have suggested that the fsr system is involved in biofilm formation and others more than the protease production. In the present study, we screened for quorum sensing inhibitors targeting fsr regulatory system from actinomycetes secondary metabolites. E.faecalis was cultured with each tested actinomycetes culture supernatant and the productions of gelatinase and GBAP(gelatinase biosynthesis activating pheromone) were tested for the first and second screenings, respectively. Culture supernatant of Streptomyces sp. QI-Y33-1 showed most potent inhibitory effect on both gelatinase and GBAP productions without inhibiting E.faecalis cell growth. The active compound named Y33-1 was isolated from the culture supernatant. Y33-1 suppressed both gelatinase and GBAP productions at submicromolar concentrations, whereas inhibiting E.faecalis cell growth at concentrations above ten micromolar. Y33-1 also suppressed gelatinase production of E.faecalis when biological or higher concentrations of synthetic GBAP was added to the culture, suggesting that Y33-1 inhibited the signal transduction of GBAP via fsr system. The structure analysis of Y33-1 and further screening for fsr inhibitors are now under progress as well as the investigation of the possibility of chemotherapy by using Y33-1.