Department of Food Science, The Pennsylvania State Universitygrid.29857.31, University Park, Pennsylvania, USA.
Microbiome Center, The Pennsylvania State Universitygrid.29857.31, University Park, Pennsylvania, USA.
Microbiol Spectr. 2022 Aug 31;10(4):e0101822. doi: 10.1128/spectrum.01018-22. Epub 2022 Jul 19.
We evaluated the ability of two strains of lactic acid bacteria (LAB) to inhibit L. monocytogenes using spot inoculation and environmental microbiome attached-biomass assays. LAB strains (PS01155 and PS01156) were tested for antilisterial activity toward 22 phylogenetically distinct L. monocytogenes strains isolated from three fruit packing environments (F1, F2, and F3). LAB strains were tested by spot inoculation onto L. monocytogenes lawns (10 and 10 CFU/mL) and incubated at 15, 20, 25, or 30°C for 3 days. The same LAB strains were also cocultured at 15°C for 3, 5, and 15 days in polypropylene conical tubes with L. monocytogenes and environmental microbiome suspensions collected from F1, F2, and F3. In the spot inoculation assay, PS01156 was significantly more inhibitory toward less concentrated L. monocytogenes lawns than more concentrated lawns at all the tested temperatures, while PS01155 was significantly more inhibitory toward less concentrated lawns only at 15 and 25°C. Furthermore, inhibition of L. monocytogenes by PS01156 was significantly greater at 15°C than higher temperatures, whereas the temperature did not have an effect on the inhibitory activity of PS01155. In the assay using attached environmental microbiome biomass, L. monocytogenes concentration was significantly reduced by PS01156, but not PS01155, when cocultured with microbiomes from F1 and F3 and incubated for 3 days at 15°C. Attached biomass microbiota composition was significantly affected by incubation time but not by LAB strain. This study demonstrates that LAB strains that may exhibit inhibitory properties toward L. monocytogenes in a spot inoculation assay may not maintain antilisterial activity within a complex microbiome. Listeria monocytogenes has previously been associated with outbreaks of foodborne illness linked to consumption of fresh produce. In addition to conventional cleaning and sanitizing, lactic acid bacteria (LAB) have been studied for biocontrol of L. monocytogenes in food processing environments that are challenging to clean and sanitize. We evaluated whether two specific LAB strains, PS01155 and PS01156, can inhibit the growth of L. monocytogenes strains in a spot inoculation and in an attached-biomass assay, in which they were cocultured with environmental microbiomes collected from tree fruit packing facilities. LAB strains PS01155 and PS01156 inhibited L. monocytogenes in a spot inoculation assay, but the antilisterial activity was lower or not detected when they were grown with environmental microbiota. These results highlight the importance of conducting biocontrol challenge tests in the context of the complex environmental microbiomes present in food processing facilities to assess their potential for application in the food industry.
我们评估了两种乳酸菌（LAB）菌株通过点接种和环境微生物附着生物量测定抑制李斯特菌的能力。LAB 菌株（PS01155 和 PS01156）针对从三个水果包装环境（F1、F2 和 F3）分离的 22 个系统发育不同的李斯特菌进行了抗李斯特菌活性测试。LAB 菌株通过点接种到李斯特菌菌落在 10 和 10 CFU/mL）并在 15、20、25 或 30°C 下孵育 3 天进行测试。相同的 LAB 菌株也在 15°C 下与从 F1、F2 和 F3 收集的李斯特菌和环境微生物组悬浮液在聚丙烯锥形管中共培养 3、5 和 15 天。在点接种试验中，PS01156 在所有测试温度下对浓度较低的李斯特菌菌落在抑制性方面均明显优于浓度较高的菌落在抑制性方面，而 PS01155 仅在 15 和 25°C 下对浓度较低的菌落在抑制性方面更明显。此外，PS01156 在 15°C 下对李斯特菌的抑制作用明显大于高温，而温度对 PS01155 的抑制活性没有影响。在使用附着环境微生物组生物量的测定中，当与 F1 和 F3 的微生物组共培养并在 15°C 下孵育 3 天时，PS01156 显著降低了李斯特菌的浓度，但 PS01155 没有。附着生物量微生物群落组成受孵育时间的显著影响，但不受 LAB 菌株的影响。这项研究表明，在点接种试验中表现出对李斯特菌抑制特性的 LAB 菌株在复杂的微生物组中可能无法保持抗李斯特菌活性。李斯特菌以前与食用新鲜农产品有关的食源性疾病爆发有关。除了常规的清洁和消毒外，乳酸菌（LAB）也被研究用于控制食品加工环境中难以清洁和消毒的李斯特菌。我们评估了两种特定的 LAB 菌株 PS01155 和 PS01156 是否可以抑制点接种和附着生物量测定中李斯特菌菌株的生长，其中它们与从水果包装设施收集的环境微生物组共培养。LAB 菌株 PS01155 和 PS01156 在点接种试验中抑制了李斯特菌，但当与环境微生物组一起生长时，其抑菌活性较低或未检测到。这些结果强调了在食品加工设施中存在的复杂环境微生物组的背景下进行生物控制挑战测试以评估其在食品工业中的应用潜力的重要性。
