HiMedia – M1816 HiCrome™ MM Agar, Modified

Principle and Interpretation
HiCrome™ MM Agar was formulated by Miller and Mallison (1) for specific isolation and detection of Salmonellae. This medium is superior to XLT4 Agar in supporting growth of Salmonella due to the presence of appropriate proportion of four sugars. HiCrome™ MM Agar, Modified is a slight modification of HiCrome™ MM Agar and designed to differentiate Enterobacteriaceae especially Salmonella from Proteus and Citrobacter group. The utilization of sugars by organisms results in pH-changes. This is used as a means of distinguishing Salmonella from competing bacteria on the basis of colony colour. Salmonella are gram negative rods in the family Enterobacteriaceae present in the stomach and intestinal tissues of human & animals and are found in their wastes. Salmonella usually are unable to ferment the sugars (2) that support growth of competing bacteria. Thus other bacteria tend to overgrow Salmonellae, masking their presence. Proteose peptone is a source of carbon, nitrogen and other essential amino acid and growth factor. Yeast extract provides vitamin especially Group B vitamins required for growth. To add to the differentiating ability of the formulation, an H2S indicator system, consisting of sodium thiosulphate and ferric ammonium citrate, is included for the visualization of hydrogen sulphide produced, resulting in the formation of colonies with black centers. Bromothymol blue act as a pH indicator. The inclusion of sugars like lactose, sucrose, xylose and cellobiose provides source of fermentable carbohydrate which stimulate the better initial growth of Salmonella cells. Presence of lactose suppresses H2S production by non-Salmonellae like Citrobacter freundii. A chromogenic mixture, present in this medium helps to differentiate between lactose fermenters and nonfermenters. Lactose fermenters give bluish green coloured colonies, which would have been impossible to differentiate with an indicator based on pH change.

原理與解釋
HiCrome™MM瓊脂由Miller和Mallison（1）專門製定 分離和檢測沙門氏菌。由於存在適當比例的四種糖，該培養基優於XLT4瓊脂，以支持沙門氏菌的生長。 HiCrome™MM Agar，Modified是對HiCrome™MM瓊脂的輕微修改，旨在區分腸桿菌科細菌，特別是Proteus和Citrobacter組的沙門氏菌。生物體對糖的利用導致pH變化。 這被用作基於菌落顏色區分沙門氏菌和競爭細菌的手段。 沙門氏菌是存在於人和動物的胃和腸組織中的腸桿菌科的革蘭氏陰性桿菌，存在於它們的廢物中。沙門氏菌通常不能發酵支持競爭細菌生長的糖（2）。因此，其他細菌往往過度生長沙門氏菌，掩蓋它們的存在。 蛋白腖是碳，氮和其他必需氨基酸和生長因子的來源。酵母提取物提供維生素，尤其是生長所需的B族維生素。為了增加配方的分化能力，包括由硫代硫酸鈉和檸檬酸鐵銨組成的H2S指示系統，用於可視化產生的硫化氫，導致形成具有黑色中心的菌落。溴百里酚藍作為pH指示劑。 包含醣類如乳糖，蔗糖，木糖和纖維二糖提供可發酵碳水化合物的來源，其刺激沙門氏菌細胞的更好的初始生長。乳糖的存在抑制非沙門氏菌如弗氏檸檬酸桿菌的產生H2S。存在於該培養基中的生色混合物有助於區分乳糖發酵罐和非發酵劑。乳糖發酵罐給出藍綠色的菌落，這是不可能區分的 使用基於pH變化的指標。