中和剂对生菜、圣女果中单核细胞增生李斯特氏菌的增菌效果

Enrichment effects of neutralizer on Listeria monocytogenes in Lactuca sativa and Lycopersicon esculentum

中文关键词:  单增李斯特菌  生菜  圣女果  中和剂  检出率

英文关键词:Listeria monocytogenes  Lactuca sativa  Lycopersicon esculentum  neutralizer  detection rate

中文摘要:

      目的 评价5种中和剂增菌液对生菜、圣女果中单核细胞增生李斯特氏菌的增菌效果, 筛选出适用于即食蔬菜中单增李斯特菌检测的增菌液。方法 采用冷冻干燥方法制备7株单增李斯特菌定量冻干样品, 选择大豆酪蛋白葡萄糖卵磷酯吐温80培养基(soya casein digest lecithin polysorbate broth, SCDLP)、改良卵磷脂肉汤(modified letheen broth, MLB)等5种含中和成分的增菌液为研究对象, 以无中和成分的缓冲蛋白胨水(buffered peptone water, BPW)为对照, 通过接种单增李斯特菌冻干标准菌株模拟果蔬真实污染情况, 考察不同重量生菜和圣女果在中和剂增菌液中的增菌情况。在此基础上, 每种蔬菜选取2种增菌效果良好的中和剂增菌液, 采用7株单增李斯特菌冻干标准菌株进行适用性验证。结果 7株单增李斯特菌冻干样品均匀性和稳定性良好。针对不同重量的生菜和圣女果, 随着检样量增加单增李斯特菌增菌受抑制程度增加; 与BPW相比5种中和剂增菌液均有助于缓解生菜对单增李斯特菌的抑制作用; 此外除UPB和D/E中和肉汤外, 其余3种中和剂增菌液对圣女果中单增李斯特菌的增菌效果均优于BPW。当检样量为325 g时, 混合增菌液(mixed enrichment broth, MIX)中单增李斯特菌的菌浓度最高, 且该增菌液适用于7株单增李斯特菌标准菌株的增菌过程。结论 生菜和圣女果中存在对单增李斯特菌的抑菌成分; 针对7株单增李斯特菌, MIX增菌效果最佳。

英文摘要:

      Objective To evaluate the enrichment effects of 5 kinds of neutralizer-containing enrichment broths on Listeria monocytogenes in Lactuca sativa and Lycopersicon esculentum, and screen out an enrichment broth suitable for the detection of Listeria monocytogenes in ready-to-eat vegetables. Methods The 7 strains of Listeria monocytogenes were quantitatively prepared as freeze-dried samples using the freeze-drying method. The 5 kinds of enrichment broths containing neutralizing agents, including soya casein digest lecithin polysorbate broth (SCDLP) and modified letheen broth (MLB), were selected as the subjects of study. Buffered peptone water (BPW) without neutralizing agents was used as the control. By inoculating the freeze-dried standard strain of Listeria monocytogenes, the study simulated real contamination scenarios in fruits and vegetables, and investigated the enrichment of the bacteria in varying weights of Lactuca sativa and Lycopersicon esculentum using the enrichment broths with neutralizer. Based on this, 2 kinds of neutralizer-containing enrichment broths with good enrichment effects were selected for each type of vegetable, and their applicability was verified using the 7 freeze-dried standard strains of Listeria monocytogenes. Results The freeze-dried samples of the 7 Listeria monocytogenes strains exhibited good uniformity and stability. For different weights of Lactuca sativa and Lycopersicon esculentum, the inhibition of Listeria monocytogenes enrichment increased with the increase in sample weight. Compared to BPW, all 5 kinds of neutralizer-containing enrichment broths to alleviating the inhibitory effect of Lactuca sativa on Listeria monocytogenes. Furthermore, except for UPB and D/E neutralizing broth, the other 3 kinds of neutralizer-containing enrichment broth exhibited superior enrichment effects on Listeria monocytogenes in Lycopersicon esculentum compared to BPW. When the sample weight was 325 g, the mixed enrichment broth (MIX) had the highest concentration of Listeria monocytogenes, and this broth was suitable for the enrichment process of the 7 standard strains of Listeria monocytogenes. Conclusion There are inhibitory components against Listeria monocytogenes in Lactuca sativa and Lycopersicon esculentum; for the 7 strains of Listeria monocytogenes, the MIX has the best enrichment effect.