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首页> 外文期刊>Food microbiology >A comparative study between overlay method and selective-differential media for recovery of stressed Enterobacter sakazakii cells from infant formula
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A comparative study between overlay method and selective-differential media for recovery of stressed Enterobacter sakazakii cells from infant formula

机译：叠加法与选择性差异培养基从婴儿配方奶粉中恢复阪崎肠杆菌应激细胞的比较研究

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This study compares the performance of different selective-differential media with the overlay method for recovery of stressed cells of Enterobacter sakazakii from infant formula milk (IFM). Five different selective-differential media were used in this study: OK medium, violet red bile agar (VRBA), Druggan-Forsythe-Iversen agar (DFI), Enterobacteriaceae enrichment (EE) agar, and fecal coliform agar (FCA). Tryptic soy agar supplemented with 0.1% sodium pyruvate (TSAP) was used as a control. The overlay method involved applying a thin layer (8 ml) of each of the selective media onto TSAP after spreading a sample onto TSAP. Reconstituted IFM was inoculated by ca 1 × 10~7CFU/ml of a mixture of four strains of E. sakazakii and subjected to different stress conditions: heat (55 ℃ for 10min), a freeze-thaw cycle (-20 ℃ for 24 h, thawed at room temperature, frozen again at - 20 ℃, and thawed), acidic pH (pH 3.56 for 15 min), alkaline pH (pH 11.04 for 15 min), and desiccation (E. sakazakii was inoculated onto powdered IFM at a level of ca 1 × 10~6 CFU/g, held at 21 ℃, water activity of the inoculated product was 0.29 and examined at 0, 15, and 30 d). No major differences were noticed between the control (TSAP) and the overlay methods. However, the overlay method recovered significantly higher numbers of stressed E. sakazakii cells compared to selective-differential media. Also, the selective-differential media exhibited some variability in terms of their capabilities to recover stressed cells of E. sakazakii. Among all the examined selective-differential media, DFI performed better for recovering stressed E. sakazakii cells. This study suggests that the overlay method may serve as a potential alternative to direct selective plating for best recovery of E. sakazakii from IFM.
机译：这项研究比较了采用覆盖法从婴儿配方奶粉（IFM）中回收阪崎肠杆菌应激细胞的不同选择性差异培养基的性能。在这项研究中使用了五种不同的选择性差异培养基：OK培养基，紫红色胆汁琼脂（VRBA），Druggan-Forsythe-Iversen琼脂（DFI），肠杆菌科细菌富集（EE）琼脂和粪大肠菌琼脂（FCA）。补充有0.1％丙酮酸钠（TSAP）的胰蛋白酶大豆琼脂用作对照。覆盖法包括在将样品铺展到TSAP之后，将每种选择培养基的薄层（8 ml）涂在TSAP上。用约1×10〜7CFU / ml的四株阪崎肠杆菌的混合物接种重组的IFM，并使其经受不同的应力条件：加热（55℃，持续10min），冻融循环（-20℃，持续24 h） ，在室温下解冻，在-20℃再次冷冻并解冻，然后在酸性pH（pH 3.56持续15分钟），碱性pH（pH 11.04持续15分钟）和干燥（阪崎肠杆菌接种于IFM粉末状）上。在21℃保持约1×10〜6 CFU / g的水平，接种产物的水分活度为0.29，分别在0,15和30 d进行检测。控件（TSAP）和叠加方法之间没有发现主要差异。但是，与选择性差异培养基相比，覆盖法回收的应激阪崎肠杆菌细胞数量明显增加。同样，选择性差异培养基在恢复阪崎肠杆菌受压细胞的能力方面表现出一些可变性。在所有检查的选择性差异培养基中，DFI在恢复应激阪崎肠杆菌细胞方面表现更好。这项研究表明，覆盖法可作为直接选择性电镀的最佳替代方法，以最佳地从IFM中回收阪崎肠杆菌。

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