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大肠菌群和大肠杆菌菌落计数方法

作者:日水生物来源:培养基厂家 日期:2016-09-14 10:25

 1.平板计数法

通常使用的培养基为紫红胆盐乳糖琼脂。准备两套平板,每个平板各加入稀释范围内的样品液1ml,另加15ml熔化并冷却至45℃的紫红胆盐乳糖琼脂充分混匀。再覆盖5ml琼脂培养基,凝固后将平板翻转,置于35℃培养24h,进行大肠菌群计数。培养后的大肠菌群为深红色菌落。通常典塑大肠菌群的菌落直径为0.5mm或稍大,紧贴菌落周围有胆盐沉淀。当几个菌落长在一起时菌落可能变小。如果食品中含有碳水化合物而不含乳糖,那么当低稀释度(既高浓度)食品加到培养基中可能导致前文提及的异常结果。对10-2或更低稀释度的平板,有必要对大肠菌群的假阳性结果进行验证,可将菌落挑选出来,转接到乳糖肉汤或麦康凯肉汤中在35℃培养后验证,或用Eijk-man试验验证大肠杆菌的存在。
2.干燥复水膜计数法

干燥复水膜是一种十分有用的大肠杆菌计数膜。用紫红胆盐培养基作为基础培养基,添加5-溴-4-氯-吲哚-β-葡萄糖苷酸以检测葡萄糖醛酸的活性。大肠杆菌在平板上为蓝色菌落并伴有气泡产生。该产品便于操作和读数,巳被作为AOAC确认为官方方法。
3.滤膜法

将滤膜(MF)和改进的选择性培养基结合使用,可检测某些样品中的大肠菌群和大肠杆菌。该方法对饮用水的检测十分有用。

 

 


1. Plate counting method
 
The medium commonly used is agar-agar, a purple gallate lactose. Prepare two sets of tablet, within the scope of each tablet to dilute liquid samples 1 ml, plus 15 ml of melting and cooling to 45 ℃ amaranthine lactose bile salt AGAR thoroughly incorporated. Covering 5 ml AGAR medium, will turn tablet after solidification, under 35 ℃ for 24 h, fecal coliform count. The cultured coliform colonies were dark red colonies. Usually, the diameter of the colony of coliform coliform coliforms is 0.5mm or slightly larger. Colonies may become smaller when several colonies grow together. If a food contains carbohydrates without lactose, the addition of a low-dilution (i.e., high concentration) food to the culture medium may result in the abnormal results mentioned above. For 10-2 or lower dilution degrees of tablets, it is necessary to verify the false positive results of fecal coliform, colony can be selected, through to lactose broth or macconkey broth cultured in 35 ℃ after verification, or use the Eijk - man test verifies the existence of e. coli.
2. Dry rehydration membrane counting method
 
Dry rehydration membrane is a very useful escherichia coli counter membrane. The activity of glutaric acid was detected by adding 5-bromo-4-chloro-indole - glycosidic acid as the basic culture medium. E. coli is a blue colony on the plate with bubbles forming. The product is easy to operate and read and has been recognized as an official method by AOAC.
3. The membrane filter technique
 
The colonic flora and e. coli in some samples can be detected by the combination of the filter membrane (MF) and the improved selective medium. This method is very useful for testing drinking water.

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