State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China; National Engineering Research Center for Functional Food, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China; Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China.
State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China; National Engineering Research Center for Functional Food, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China; Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China.
J Dairy Sci. 2021 Mar;104(3):2641-2653. doi: 10.3168/jds.2020-19456. Epub 2020 Dec 25.
Staphylococcus aureus is a widespread foodborne pathogen that threatens human health. In particular, multidrug-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) are emerging problems in modern health care, food safety, and animal health, which require the development of new antimicrobials to replace overused conventional antibiotics. Dairy products can potentially act as vehicles for the transmission of S. aureus and other antibiotic-resistant strains from the farm into the general human population, and should be controlled during the production and storage process. Recently, bacteriophage endolysins, which degrade the cell wall that is indispensable for bacteria, have been deemed promising antimicrobial agents. In this study, one endolysin, LysGH15, demonstrated prominent antimicrobial efficacy against S. aureus, as did its catalytic domain, cysteine, histidine-dependent amidohydrolase/peptidases (CHAP) alone. The LysGH15 and CHAP exhibited different characteristics in one MRSA strain (MRSA 2701), reaching the highest activity under different conditions (35°C and pH 6.0 for LysGH15, 40°C and pH 9.0 for CHAP). A difference in the sensitivity of LysGH15 and CHAP to NaCl concentration was found, where the lytic activity of LysGH15 depends strongly on its binding domain's binding capacity, which is positively correlated with the NaCl concentration, whereas the CHAP activity showed a negative correlation with the NaCl concentration. When the NaCl concentration was 450 mM, the lytic activity of LysGH15 reached its peak, whereas the lytic activity of CHAP was the highest in the absence of NaCl. The difference in NaCl sensitivity between LysGH15 and CHAP may be due to the sensitivity of the SH3b binding protein of LysGH15 to NaCl. The CHAP was tested as a biopreservative in whole and skim milk and exerted effective control against S. aureus (declined by approximately 2.5 log cfu/mL when incubated at 4°C for 8 h), which suggests promise for application in dairy products.
金黄色葡萄球菌是一种广泛存在的食源性致病菌，威胁着人类健康。特别是耐甲氧西林金黄色葡萄球菌（MRSA）等多药耐药菌在现代医疗保健、食品安全和动物健康领域不断涌现，这就需要开发新的抗菌药物来替代过度使用的传统抗生素。乳制品可能会成为金黄色葡萄球菌和其他抗生素耐药菌株从农场传播到普通人群的载体，因此在生产和储存过程中应加以控制。最近，溶菌酶内切酶，即能够降解细菌细胞壁的酶，被认为是有前途的抗菌药物。在这项研究中，一种溶菌酶内切酶 LysGH15 对金黄色葡萄球菌表现出显著的抗菌效果，其催化结构域半胱氨酸、组氨酸依赖酰胺水解酶/肽酶（CHAP）也表现出同样的效果。LysGH15 和 CHAP 在一株耐甲氧西林金黄色葡萄球菌（MRSA 2701）中表现出不同的特性，在不同条件下（LysGH15 在 35°C 和 pH 6.0 时活性最高，CHAP 在 40°C 和 pH 9.0 时活性最高）达到最高活性。LysGH15 和 CHAP 对 NaCl 浓度的敏感性存在差异，其中 LysGH15 的溶菌活性强烈依赖于其结合域的结合能力，而结合能力与 NaCl 浓度呈正相关，而 CHAP 活性与 NaCl 浓度呈负相关。当 NaCl 浓度为 450 mM 时，LysGH15 的溶菌活性达到峰值，而当不存在 NaCl 时，CHAP 的溶菌活性最高。LysGH15 和 CHAP 对 NaCl 敏感性的差异可能是由于 LysGH15 的 SH3b 结合蛋白对 NaCl 的敏感性。CHAP 被测试作为全脂和脱脂牛奶中的生物防腐剂，对金黄色葡萄球菌具有有效控制作用（在 4°C 孵育 8 小时时下降约 2.5 log cfu/mL），这表明其在乳制品中的应用具有潜力。
