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月桂基硫酸盐胰蛋白胨（LST）肉汤
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品牌名称：$brandModel.Title(进口品牌)型号： 原产地：中国大陆 发布时间：2018/3/2 9:40:03更新时间：2024/10/21 16:53:01
产品摘要：月桂基硫酸盐胰蛋白胨（LST）肉汤Lauryl Tryptose Broth）简称LST培养基，是大肠菌选择性液体培养基，用于检测食品、水、奶制品中的大肠菌群和大肠埃希氏菌。本产品配方采用美国公众健康协会APHA规定配方，用于检测水和污水中的大肠菌群，同时也是《细菌学分析手册》采用的配方。
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详细内容
培养基名称月桂基硫酸盐胰蛋白示肉汤，十二烷基硫酸盐肉汤，LST培养基
英文名称:Lauryl Sulphate Broth，Lauryl Tryptose Broth，LST
培养基类型:选择性培养基
产品规格:250g 查看其它规格
保存条件:密封，阴凉干燥处保存。制备好的培养基2-8°C保存。
产品性状:麦秸色粉末。
琥珀色透明液体。在冰箱中冷藏的液体培养基会形成沉淀或浑浊，在室温下变清澈。
注意事项:避免摄入、呼入、皮肤接触。配制时在通风橱中进行，戴口罩、手套、护目镜。
产品介绍：用途：用于多管发酵法测定大肠菌群和粪大肠菌群。（GB 4789.3—2010、GB/T 4789.39—2008 、SN 0169—2010）
LST培养基工作原理
大肠菌群时革兰氏阴性杆菌，能够快速发酵乳糖产气（水不溶性气体）。更为准确的定义是35°C条件下能够在LST培养基和BGLB培养基中生长，并且发酵乳糖产气的革兰氏阴性杆菌。在44.5°C条件下，还能够在EC肉汤中发酵乳糖产气的属于大肠菌群的一个子集——粪大肠菌群。
表面活性剂如胆盐、蓖麻油酸钠，一直以来作为抑制成分，用于配制选择性培养基。十二烷基硫酸钠（SDS）在大肠菌选择性培养基中效果，完全阻止革兰氏阳性菌生长。十二烷基硫酸盐胰蛋白示肉汤可以在小量接种的情况下支持大肠菌的密集生长并产生大量气体。该培养基另外一个优点是可用于直接检测吲哚的存在。如果需要，可以在培养后加入指示剂。
向培养基中加入4-甲基伞型酮-β-D-葡糖苷酸（MUG）可以提高检测大肠埃希氏菌的灵敏度。不产气的大肠埃希菌菌株也能用MUG鉴别。MUG是一种生荧光化合物。大肠埃希氏菌具有合成Beta-葡萄糖苷酶的能力，水解MUG生成荧光化合物。在366nm波长的紫外灯下，培养基显荧光，实现大肠埃希氏菌的快速检测。
实验方法
Lauryl Tryptose Broth is recommended for the detection ａnd enumeration of coliform organisms in water ａnd milk products, especially in the control of ice-cream manufacture ａnd in dairy hygiene. A suggested procedure ( Dyett7 ) is as follows:
1.Inoculate samples of ice cream into tubes of Lauryl Tryptose Broth in the manner normally employed in the MacConkey test. Examine the tubes after overnight incubation at 35°C and, if no gas is visible, examine again at the end of 48 hours’ incubation.
2.From every tube showing fermentation (primary fermentation), two further tubes of Lauryl Tryptose Broth are inoculated, ａnd these are incubated at 35°C ａnd 44°C respectively. It is advisable that the tube to be incubated at 44°C be warmed in a water bath at this temperature before inoculation.
3.After the two tubes of Lauryl Tryptose Broth have been inoculated for secondary fermentation, test the original primary fermentation tube (which was inoculated directly with ice cream) for indole production. A positive reaction suggests the presence of Escherichia coli ａnd confirmation will be obtained later with the secondary fermentation from the 44°C bath. A negative indole reaction in the primary fermentation tube indicates the absence of E. coli.
4.Check the 44°C incubated secondary broth for fermentation after seven hours. If positive, test for indole production with either Ehrlich or Kovac’s reagent. Due to the lauryl sulphate present, shaking the reagent culture mixture forms a persistent emulsion which interferes with the test. This may be avoided by shaking with ether, which separates rapidly, ａnd then adding Kovac’s reagent to the layer without shaking.
5.If fermentation has not occurred after seven hours, leave the tube overnight at 44°C ａnd test the following day. A positive indole reaction in a broth that has produced gas at 44°C indicates the presence of E. coli.
6.The tube at 35°C is incubated for 24 hours. If no fermentation occurs, the primary fermentation is assumed to be due to organisms other than coliforms. False positives are not uncommon in the primary fermentation tubes, due to fermentation of the sucrose in the added ice cream by organisms other than coliforms.
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