The increasing clinical incidence of antibiotic resistance in bacteria is a major global health care issue. Rampant use of antimicrobials is one of the major reasons of the dramatic rise in antibiotic-resistant bacterial strains. Suitable animal models are required to improve our understanding of bacterial pathogenicity, evolution and search for novel antibiotics. The larvae of the silk moth (commonly called silkworm), Bombyx mori, have been used as an animal model for testing the pathogenicity of a clinically isolated strain of enterohemorrhagic Escherichia coli O157:H7 upon injection through hemolymph. Here, we show that a foodborne E. coli O157:H7 strain can kill silkworm larvae upon injection through either hemolymph (blood) or midgut. Bacterial number in the hemolymph started to increase after 3 h of injection into hemolymph, while the number of viable circulating hemocytes decreased. Administration of four well-known antibiotics into the larval hemolymph up to 100 µg per larva showed therapeutic effect with varying efficacies against E. coli O157:H7 with ceftriaxone and imipenem showing better effect. Our findings indicate that silkworm larvae can be used as an animal model to screen for novel antibiotics that are effective against E. coli O157:H7.

中文翻译：

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抗生素对丝蛾幼虫动物模型中大肠杆菌O157:H7的治疗作用

细菌中抗生素耐药性的临床发病率不断增加是一个主要的全球卫生保健问题。抗菌药物的大量使用是抗生素耐药菌株急剧增加的主要原因之一。需要合适的动物模型来提高我们对细菌致病性、进化和寻找新型抗生素的理解。蚕蛾（通常称为家蚕）的幼虫家蚕 (Bombyx mori) 已被用作动物模型，用于测试通过血淋巴注射的临床分离的肠出血性大肠杆菌 O157:H7 菌株的致病性。在这里，我们展示了食源性大肠杆菌 O157:H7 菌株可以在通过血淋巴（血液）或中肠注射后杀死家蚕幼虫。注入血淋巴3小时后，血淋巴中的细菌数量开始增加，而活循环血细胞的数量减少。将四种众所周知的抗生素施用到幼虫血淋巴中，每只幼虫 100 µg 显示出治疗效果，对大肠杆菌 O157:H7 具有不同的疗效，头孢曲松和亚胺培南显示出更好的效果。我们的研究结果表明，蚕幼虫可用作动物模型来筛选对大肠杆菌 O157:H7 有效的新型抗生素。