Department of Microbiology and Infection, Faculty of Medicine, Kochi University, Kochi, Japan.
PLoS One. 2011;6(10):e26648. doi: 10.1371/journal.pone.0026648. Epub 2011 Oct 25.
Some bacterial strains of the multidrug-resistant Gram-positive bacteria Enterococcus faecalis can significantly reduce the efficacy of conventional antimicrobial chemotherapy. Thus, the introduction of bacteriophage (phage) therapy is expected, where a phage is used as a bioagent to destroy bacteria. E. faecalis phage ΦEF24C is known to be a good candidate for a therapeutic phage against E. faecalis. However, this therapeutic phage still produces nonuniform antimicrobial effects with different bacterial strains of the same species and this might prove detrimental to its therapeutic effects. One solution to this problem is the preparation of mutant phages with higher activity, based on a scientific rationale. This study isolated and analyzed a spontaneous mutant phage, ΦEF24C-P2, which exhibited higher infectivity against various bacterial strains when compared with phage ΦEF24C. First, the improved bactericidal effects of phage ΦEF24C-P2 were attributable to its increased adsorption rate. Moreover, genomic sequence scanning revealed that phage ΦEF24C-P2 had a point mutation in orf31. Proteomic analysis showed that ORF31 (mw, 203 kDa) was present in structural components, and immunological analysis using rabbit-derived antibodies showed that it was a component of a long, flexible fine tail fiber extending from the tail end. Finally, phage ΦEF24C-P2 also showed higher bactericidal activity in human blood compared with phage ΦEF24C using the in vitro assay system. In conclusion, the therapeutic effects of phage ΦEF24C-P2 were improved by a point mutation in gene orf31, which encoded a tail fiber component.
某些多重耐药革兰阳性菌粪肠球菌的细菌株可显著降低常规抗菌化疗的疗效。因此，人们期望引入噬菌体（phage）治疗，即使用噬菌体作为生物制剂来破坏细菌。已知粪肠球菌噬菌体 ΦEF24C 是针对粪肠球菌的治疗性噬菌体的候选者。然而，这种治疗性噬菌体对同种细菌的不同菌株仍产生不均匀的抗菌效果，这可能对其治疗效果有害。解决此问题的一种方法是基于科学依据制备具有更高活性的突变噬菌体。本研究分离并分析了一种自发突变噬菌体 ΦEF24C-P2，与噬菌体 ΦEF24C 相比，其对各种细菌菌株的感染力更高。首先，噬菌体 ΦEF24C-P2 的杀菌效果得到改善归因于其吸附率的提高。此外，基因组序列扫描表明噬菌体 ΦEF24C-P2 在 orf31 中存在点突变。蛋白质组学分析表明，ORF31（mw，203 kDa）存在于结构成分中，并且使用兔源性抗体进行的免疫分析表明，它是从尾部延伸的长而灵活的精细尾丝的组成部分。最后，与噬菌体 ΦEF24C 相比，噬菌体 ΦEF24C-P2 在体外检测系统中在人血中也显示出更高的杀菌活性。总之，orf31 基因的点突变导致噬菌体 ΦEF24C-P2 的治疗效果得到改善，该基因编码尾丝成分。
