Havelaar A H, During M
Laboratory of Water and Food Microbiology, National Institute of Public Health and Environmental Hygiene, Bilthoven, The Netherlands.
J Appl Bacteriol. 1988 Jan;64(1):89-98. doi: 10.1111/j.1365-2672.1988.tb02432.x.
The direct plating (DP) method for enumerating Escherichia coli in food was adapted for water analysis by membrane filtration and a standardized protocol was described. The DP method was found to give equal or better recoveries of E. coli than a membrane filtration method using 0.1% sodium lauryl sulphate agar; the repeatability of the DP method was markedly better. The necessity to transfer membranes from the non-selective medium tryptone soy agar (TSA) to the selective medium tryptone bile agar (TBA) after pre-incubation for 4 h was considered disadvantageous for practical purposes. A double-layer method, where the membrane filter is placed on a layer of TSA poured over TBA, with incubation in an incubator that automatically switches from 37 degrees to 44 degrees C after 4 h, was found to be an acceptable alternative. Recovery of E. coli and inhibition of competitive flora were equal or only slightly less than for the standard DP method.
用于食品中大肠杆菌计数的直接平板法（DP）通过膜过滤适用于水分析，并描述了标准化方案。发现DP法对大肠杆菌的回收率与使用0.1%十二烷基硫酸钠琼脂的膜过滤法相当或更高；DP法的重复性明显更好。预孵育4小时后，有必要将膜从非选择性培养基胰蛋白胨大豆琼脂（TSA）转移到选择性培养基胰蛋白胨胆盐琼脂（TBA），从实际操作角度考虑这是不利的。发现一种双层法是一种可接受的替代方法，即将膜过滤器放置在浇在TBA上的一层TSA上，并在孵育4小时后自动从37℃切换到44℃的培养箱中孵育。大肠杆菌的回收率和对竞争性菌群的抑制与标准DP法相当或仅略低。
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