用途:用于粪大肠菌群、大肠杆菌的测定。

成分(g/L)

胰蛋白胨             20.0

乳糖                  5.0

氯化钠                5.0

磷酸氢二钾            4.0

磷酸二氢钾            1.5

三号胆盐              1.5

pH值 6.9±0.1        25℃

用法

称取本品37.0g,加热搅拌溶解于 1000ml 蒸馏水中,分装到有倒立发酵管的16mm*150mm试管中,每管8ml,121℃高压灭菌 15 分钟,备用。

质量控制和典型特征在 44.5℃培养 24-48h,粪大肠菌群和大肠杆菌产生气体,在倒立小发酵管中有气泡。

EC肉汤培养基工作原理

大肠菌群是革兰氏阴性杆菌，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，24-48h内，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，发酵乳糖产酸产气的是大肠埃希氏菌。

胰蛋白月示提供大肠菌群生长所需营养物质。胆盐是革兰氏阳性球菌和产芽孢菌抑制剂，尤其是粪链球菌和芽孢杆菌。乳糖是大肠菌可发酵糖类。磷酸盐是pH缓冲系统，与氯化钠一起可以通过减慢乳糖发酵微生物生长速度来改善产气量。

实验方法

1. Milk ａnd Milk Products/Presumptive E. coli2 (ISO)

Tubes containing inverted Durham tubes with single ａnd double strength Lauryl Tryptose Broth are inoculated with samples as described in the standard method. Incubate at 37°C for 24-48 hours ａnd examine for gas production. Inoculate tubes showing gas production into a new series of tubes containing 10ml of EC Broth containing inverted Durham tubes, ａnd incubate at 44°C for 24-48 hours. Transfer an inoculum from tubes giving rise to gas formation to tubes containing Tryptone Water , ａnd incubate for 24-48 hours at 44°C. Examine for indole production ａnd calculate the Most Probable Number (MPN) of presumptive E. coli. For full details please refer to the ISO Standard Method.

2. Faecal Coliform Test (APHA)

For differentiation of faecal coliforms inoculate EC Broth fermentation tubes containing inverted Durham tubes, ａnd incubate in a water bath at 44.5°C for 24 ± 2°C hours. Gas production ａnd growth within 24 hours or less is considered a positive faecal coliform reaction. For full details please refer to the APHA Standard Method3.

3. Confirmatory Test for E. coli (FDA/BAM)

From each gassing Lauryl Tryptose Broth tube, transfer a loopful of suspension to EC Broth tubes containing inverted Durham tubes. Incubate at 45.5°C, ａnd examine for gas production after 24 ａnd 48 hours. Gassing tubes are streaked onto EMB Agar ａnd incubated at 35°C for 18-24 hours. Transfer 2 suspicious colonies from each plate onto PCA ,incubate fot 18-24 hours at 35°C ａnd confirm with morphological ａnd biochemical tests. For full details please refer to the FDA/BAM Standard Method4.