The discovery of novel therapeutic antimicrobials has become an urgent issue in response to the global crisis of the spread of multi-drug-resistant bacteria. In this report, we propose an efficient screening method for antimicrobial agents with therapeutic potential from soil bacteria. With this method, colonies of the soil bacteria were formed first on agar plates containing only an extract of soil, followed by an overlay of soft agar containing the pathogens, an antibiotic target. Then, we selected the colonies that formed the inhibitory zones on soft agar and evaluated the therapeutic efficacy of their culture supernatants using a silkworm bacterial infection model. Using Staphylococcus aureus as an indicator strain to obtain bacteria that produce therapeutically effective antimicrobials, we succeeded in reducing the screening size by 20-fold compared to the conventional method. An analysis of 86 antibiotics producers identified in this study indicated that the majority belonged to Streptomyces sp. and Lysobacter sp., well-known producers of secondary metabolites. Besides, the presence of eight genera and 37 species among the identified species indicated the diversity of antibiotic producers. Based on the finding of our study, we propose this method as an efficient way to discover novel antimicrobial agents that are therapeutically effective.

新型治疗性抗菌药物的发现已成为应对全球多重耐药菌传播危机的紧迫问题。在本报告中，我们提出了一种从土壤细菌中筛选具有治疗潜力的抗菌剂的有效方法。使用这种方法，土壤细菌的菌落首先在仅含有土壤提取物的琼脂平板上形成，然后覆盖含有病原体（抗生素靶标）的软琼脂。然后，我们选择了在软琼脂上形成抑制区的菌落，并使用家蚕细菌感染模型评估了它们培养上清液的治疗效果。使用金黄色葡萄球菌作为获得产生治疗有效抗菌剂的细菌的指示菌株，与传统方法相比，我们成功地将筛选规模缩小了 20 倍。对本研究中确定的 86 家抗生素生产商的分析表明，大多数属于链霉菌属。和Lysobacter sp.，众所周知的次级代谢产物生产者。此外，在已鉴定的物种中存在8属37种，表明抗生素生产者的多样性。根据我们的研究结果，我们建议将此方法作为发现治疗有效的新型抗菌剂的有效方法。