HiMedia – M1465andM1453 Rapid HiColiform™ Agar / Broth

Principle and Interpretation
The Rapid HiColiform™ Agar is modification of LMX Broth described by Manafi and Kneifel (2). These media are useful for the detection and confirmation of Escherichia coli and total coliforms in water samples on the basis of chromogenic and fluorogenic substrates (1-6). Peptone special, which is rich in tryptophan provides essential growth nutrients and is useful for the simultaneous detection of indole production. Sorbitol provides the carbon source. The phosphate salts provide buffering action for rapid growth of coliforms. Sodium lauryl sulphate makes the medium selective by inhibiting accompanying microflora, especially the gram-positive organisms. The fluorogenic substrate is split by enzyme b-D-glucuronidase, which is specifically found in E. coli. The reaction is indicated by a blue fluorescence under UV light. The presence of total coliforms is indicated by a blue-green colour of the broth due to cleavage of chromogenic substrate. IPTG, a highly stable synthetic analog of lactose induces synthesis of b-D-glucuronidase. In agar medium, 2-3 drops of Kovac’s reagent is added over the suspected colonies. Change in the colour of colony to red confirms E. coli. Broth medium is overlayed with Kovac’s reagent and formation of red ring confirms E. coli. If fluorescence is negative after 24 hours of incubation, continue incubation for another 24 hours without performing the indole test.

原理與解釋
Rapid HiColiform™瓊脂是Manafi和Kneifel描述的LMX肉湯的改良（2）。這些培養基可用於基於髮色和熒光底物檢測和確認水樣中的大腸桿菌和總大腸菌群（1-6）。 富含色氨酸的蛋白腖特性提供必需的生長營養素，可用於同時檢測吲哚的產生。山梨糖醇提供碳源。磷酸鹽為大腸桿菌的快速生長提供緩衝作用。十二烷基硫酸鈉通過抑制伴隨的微生物群，特別是革蘭氏陽性生物，使培養基具有選擇性。熒光底物被酶b-D-葡醣醛酸糖苷酶分裂，其特異性地存在於大腸桿菌中。在UV光下通過藍色熒光指示反應。由於髮色底物的裂解，發酵液的藍綠色表示總大腸菌群的存在。 IPTG，一種高度穩定的乳糖合成類似物 b-D-葡醣醛酸糖苷酶的合成。在瓊脂培養基中，在可疑菌落上加入2-3滴Kovac試劑。菌落顏色變為紅色證實大腸桿菌。肉湯培養基覆蓋有Kovac試劑，紅環的形成證實了大腸桿菌。如果孵育24小時後熒光為陰性，則繼續孵育24小時而不進行吲哚試驗。