Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares s/n, 33300 Villaviciosa, Asturias, Spain; DairySafe Group, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Spain; Microbiology Department, Faculty of Veterinary Medicine, Alexandria University, Egypt; Animal Health Research Institute, Agricultural Research Center (ARC), Egypt.
Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares s/n, 33300 Villaviciosa, Asturias, Spain; DairySafe Group, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Spain.
Int J Food Microbiol. 2023 Aug 16;399:110227. doi: 10.1016/j.ijfoodmicro.2023.110227. Epub 2023 Apr 29.
Staphylococcus aureus is a Gram-positive human opportunistic pathogen that may also cause food poisoning because of the ability of some strains to produce heat stable enterotoxins that can persist in food even after the pathogen is successfully eliminated. In this context, biopreservation may be a forward-looking strategy to help eliminate staphylococcal contamination in dairy products by using natural compounds. However, these antimicrobials exhibit individual limitations that may be overcome by combining them. This work investigates the combination of a virulent bacteriophage, phiIPLA-RODI, a phage-derived engineered lytic protein, LysRODIΔAmi, and the bacteriocin nisin for the elimination of S. aureus during lab-scale cheese production at two CaCl concentrations (0.2 % and 0.02 %), and subsequent storage at two different temperatures (4 °C and 12 °C). In most of the assayed conditions, our results demonstrate that the combined action of the antimicrobials led to a greater reduction of the pathogen population than the compounds individually, albeit this effect was additive and not synergistic. However, our results did show synergy between the three antimicrobials for reducing the bacterial load after 14 days of storage at 12 °C, temperature at which there is growth of the S. aureus population. Additionally, we tested the impact of the calcium concentration on the activity of the combination treatment and observed that higher CaCl levels led to a notable increase in endolysin activity that allowed the utilization of approximately 10-times less protein to attain the same efficacy. Overall, our data show that the combination of LysRODIΔAmi with nisin and/or phage phiIPLA-RODI, and an increase in the calcium concentration are successful strategies to decrease the amount of protein required for the control of S. aureus contamination in the dairy sector with a low potential for resistance selection, thereby reducing costs.
金黄色葡萄球菌是一种革兰氏阳性的人类机会致病菌，由于某些菌株能够产生耐热肠毒素，即使在病原体被成功消除后，这些毒素仍能在食物中存活，因此也可能导致食物中毒。在这种情况下，生物保鲜可能是一种前瞻性策略，可以利用天然化合物帮助消除乳制品中的葡萄球菌污染。然而，这些抗菌剂各自存在限制，通过联合使用可能会克服这些限制。本研究调查了烈性噬菌体 phiIPLA-RODI、噬菌体衍生的工程溶菌蛋白 LysRODIΔAmi 和细菌素乳链菌肽联合使用，以消除实验室规模奶酪生产过程中金黄色葡萄球菌污染的情况，同时在两种 CaCl2 浓度（0.2%和 0.02%）下，以及在两种不同温度（4°C 和 12°C）下随后的储存。在大多数检测条件下，我们的结果表明，与单独使用化合物相比，抗菌剂的联合作用导致病原体数量的减少更大，尽管这种效果是相加的，而不是协同的。然而，我们的结果确实表明，在 12°C 下储存 14 天后，三种抗菌剂联合使用可以协同减少细菌负荷，而在这个温度下，金黄色葡萄球菌的数量会增加。此外，我们测试了钙浓度对组合处理活性的影响，发现较高的 CaCl2 水平导致内溶素活性显著增加，这使得使用大约 10 倍少的蛋白就可以达到相同的效果。总的来说，我们的数据表明，LysRODIΔAmi 与乳链菌肽和/或噬菌体 phiIPLA-RODI 联合使用，以及增加钙浓度是减少控制乳制品中金黄色葡萄球菌污染所需蛋白量的成功策略，同时具有低抗性选择潜力，从而降低成本。
