Phage lytic proteins are promising antimicrobials that could complement conventional antibiotics and help to combat multi-drug resistant bacteria that cause important human and animal infections. Here, we report the characterization of endolysin LysRODI (encoded by staphylophage phiIPLA-RODI) and its application as a prophylactic mastitis treatment. The main properties of LysRODI were compared with those of endolysin LysA72 (encoded by staphylophage phiIPLA35) and the chimeric protein CHAPSH3b (derived from the virion-associated peptidoglycan hydrolase HydH5 and lysostaphin). Time-kill experiments performed with Staphylococcus aureus and Staphylococcus epidermidis demonstrated that the killing rate of LysRODI and CHAPSH3b is higher than that of LysA72 (0.1 μM protein removed 107 CFU/ml of S. aureus in 30 min). Of note, all proteins failed to select resistant mutants as bacterial exposure to sub-lethal concentrations of the proteins did not alter the MIC values. Additionally, LysRODI and CHAPSH3b were non-toxic in a zebrafish embryo model at concentrations near the MIC (0.5 and 0.7 μM, respectively). Moreover, these two proteins significantly reduced mortality in a zebrafish model of systemic infection. In contrast to LysRODI, the efficacy of CHAPSH3b was dose-dependent in zebrafish, requiring higher-dose treatments to achieve the maximum survival rate. For this reason, LysRODI was selected for further analysis in mice, demonstrating great efficacy to prevent mammary infections by S. aureus and S. epidermidis. Our findings strongly support the use of phage lytic proteins as a new strategy to prevent staphylococcal mastitis.

中文翻译：

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噬菌体溶解蛋白LysRODI可预防小鼠葡萄球菌性乳腺炎。

噬菌体裂解蛋白是有前途的抗菌剂，可以补充常规抗生素并有助于对抗引起重大人类和动物感染的耐多药细菌。在这里，我们报道了溶血素溶素LysRODI（由噬菌体phiIPLA-RODI编码）的表征及其在预防性乳腺炎治疗中的应用。将LysRODI的主要特性与内溶素LysA72（由噬菌体phiIPLA35编码）和嵌合蛋白CHAPSH3b（来自与病毒体相关的肽聚糖水解酶HydH5和溶葡萄球菌素）进行比较。用金黄色葡萄球菌和表皮葡萄球菌进行的时间杀灭实验表明，LysRODI和CHAPSH3b的杀灭率高于LysA72（0.1μM的蛋白质在30分钟内去除了107 CFU / ml的金黄色葡萄球菌）。值得注意的是 所有细菌均未能选择抗性突变体，因为细菌暴露于亚致死浓度的蛋白质不会改变MIC值。此外，LysRODI和CHAPSH3b在斑马鱼胚胎模型中的MIC浓度附近（分别为0.5和0.7μM）是无毒的。此外，在斑马鱼全身感染的模型中，这两种蛋白质显着降低了死亡率。与LysRODI相反，CHAPSH3b的功效在斑马鱼中是剂量依赖性的，需要更高剂量的治疗才能达到最大存活率。因此，选择LysRODI进行小鼠进一步分析，显示出预防金黄色葡萄球菌和表皮葡萄球菌乳腺感染的巨大功效。我们的发现强烈支持使用噬菌体裂解蛋白作为预防葡萄球菌性乳腺炎的新策略。