Instituto de Productos Lácteos de Asturias, Spain.
Int J Food Microbiol. 2010 Jul 15;141(3):151-5. doi: 10.1016/j.ijfoodmicro.2010.04.029. Epub 2010 May 8.
Phage-encoded endolysins are recently considered as new biocontrol tools to inhibit pathogens in food. In this work, we have studied the ionic requirements for optimal lytic activity of LysH5, the endolysin encoded by the staphylococcal bacteriophage phi-SauS-IPLA88. LysH5 activity was inhibited by the presence of Mn(++) and Zn(++) and enhanced by Ca(++), Mg(++) and NaCl. When LysH5 was combined with nisin, a bacteriocin currently used as a biopreservative in food, a strong synergistic effect was observed. The Minimum Inhibitory Concentrations of nisin and LysH5 were reduced 64- and 16-fold, respectively, as determined in checkerboard microtitre tests. In addition, nisin enhanced 8-fold the lytic activity of LysH5 on cell suspensions. The synergy observed in vitro was confirmed in challenge assays in pasteurized milk contaminated with S. aureus Sa9. Clearance of the pathogen was only achieved by the combined activity of both antimicrobials. As far as we know, this is the first study that exploits the possibilities of hurdle technology combining a phage-encoded endolysin and the bacteriocin nisin for efficient S. aureus inhibition in milk.
噬菌体编码的内溶素最近被认为是抑制食品中病原体的新型生物防治工具。在这项工作中，我们研究了葡萄球菌噬菌体 phi-SauS-IPLA88 编码的内溶素 LysH5 的最佳裂解活性的离子要求。Mn(++)和 Zn(++)的存在抑制了 LysH5 的活性，而 Ca(++)、Mg(++)和 NaCl 则增强了其活性。当 LysH5 与目前在食品中用作生物防腐剂的细菌素乳链菌肽联合使用时，观察到强烈的协同作用。在棋盘微量滴定试验中，最小抑菌浓度 (Minimum Inhibitory Concentrations) 的测定结果表明，乳链菌肽和 LysH5 的最小抑菌浓度分别降低了 64 倍和 16 倍。此外，乳链菌肽将 LysH5 对细胞悬浮液的裂解活性增强了 8 倍。在巴氏奶污染金黄色葡萄球菌 Sa9 的挑战试验中证实了体外观察到的协同作用。只有通过两种抗菌剂的联合作用才能清除病原体。据我们所知，这是第一项利用噬菌体编码的内溶素和细菌素乳链菌肽的障碍技术，在牛奶中有效抑制金黄色葡萄球菌的研究。
