College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning, 110866, China.
Beijing Vegetable Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing Key Laboratory of Agricultural Products of Fruits and Vegetables Preservation and Processing, Key Laboratory of Vegetable Postharvest Processing, Ministry of Agriculture and Rural Affairs, Beijing, 100097, China.
Food Microbiol. 2022 Aug;105:103885. doi: 10.1016/j.fm.2021.103885. Epub 2021 Aug 13.
Cucumber is usually eaten as a raw vegetable and easily contaminated by pathogenic microorganisms; the contamination process includes colonization, proliferation, and biofilm formation. In this study, plate counting was used to determine the stage of E. coli O157:H7 colonization/proliferation in cucumber epidermis and fruit. Expression of E. coli genes associated with adhesion, movement and oxidative stress response during colonization and proliferation in cucumber was evaluated with fluorescence real-time quantitative PCR. Scanning electron microscopy imaging was used to observe biofilm formation over time in different cucumber tissues at 4 °C and 25 °C. During colonization (at 0-45 and 0-30 min in epidermis and fruit, respectively), escV, fliC, espA, escN, espF, espG, espZ, nleA, tir, and ycbR genes were upregulated. The escC was downregulated, while map and espH expression did not vary. During proliferation (after 45 and 30 min in epidermis and fruit, respectively), fliC was downregulated, whereas the outer membrane protein intimin gene and oxidative stress genes rpoS and sodB were upregulated. During storage, 25 °C was more favorable for biofilm formation than 4 °C. The ability of biofilm formation on the vascular system was the strongest, and the biofilm on epidermis sloughed off earlier than that on other tissues. Clarifying the process of E. coli O157:H7 contaminating cucumbers provided useful information for the development of prevention and control methods of fresh-cut cucumber.
黄瓜通常作为生蔬菜食用，容易被病原微生物污染；污染过程包括定植、增殖和生物膜形成。在本研究中，平板计数法用于确定大肠杆菌 O157:H7 在黄瓜表皮和果实中的定植/增殖阶段。通过荧光实时定量 PCR 评估大肠杆菌在定植和增殖过程中与粘附、运动和氧化应激反应相关的基因表达。扫描电子显微镜成像用于观察不同黄瓜组织在 4°C 和 25°C 下随时间形成生物膜的情况。在定植阶段（分别在表皮和果实中 0-45 和 0-30 分钟），escV、fliC、espA、escN、espF、espG、espZ、nleA、tir 和 ycbR 基因上调。escC 下调，而 map 和 espH 表达没有变化。在增殖阶段（分别在表皮和果实中 45 和 30 分钟后），fliC 下调，而外膜蛋白 intiminin 基因和氧化应激基因 rpoS 和 sodB 上调。在贮藏过程中，25°C 比 4°C 更有利于生物膜形成。在血管系统上形成生物膜的能力最强，表皮上的生物膜比其他组织上的生物膜更早脱落。阐明大肠杆菌 O157:H7 污染黄瓜的过程为开发鲜切黄瓜的预防和控制方法提供了有用信息。
