HiMedia – M1393 HiCrome™ MM Agar

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. Most differential and selective media are formulated with one or more sugars and pH indicators respectively. 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 usually are unable to ferment the sugars (2) that support growth of competing bacteria. Thus other bacteria tend to overgrow Salmonellae,masking their presence. The inclusion of sugars like mannitol, cellobiose and trehalose stimulate the better initial growth of Salmonella cells. However, the low concentrations of these sugars do not interfere with the utilization of protein and H2S production. Presence of lactose suppresses H2 S 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 impossibleto differentiate with an indicator based on pH change. Inclusion of tergitol 4 (included in chromogenic mixture) in the medium suppresses the presence of Proteus and Providencia colonies. Peptone and HM peptone B provide nitrogenous and carbonaceous compounds, long chain amino acids, vitamins and other essential growth nutrients.

原理與解釋
HiCrome™MM瓊脂由Miller和Mallison（1）配製用於特異性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。大多數差異和選擇性培養基配製有一種或多種糖和pH 指標分別。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。包含醣類如甘露醇，纖維二糖 和海藻糖刺激沙門氏菌細胞更好的初始生長。 然而，這些糖的低濃度不會干擾蛋白質和H2S產生的利用。乳糖的存在抑制H2 非沙門氏菌如弗氏檸檬酸桿菌（Citrobacter freundii）生產。 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。乳糖發酵罐給出帶藍綠色的菌落，根據pH變化，這種菌落不可能與指示劑區分開來。在培養基中包含tergitol 4（包含在生色混合物中）抑制變形桿菌和普羅威登斯菌落的存在。蛋白腖和HM 蛋白腖B提供含氮和含碳化合物，長鏈氨基酸，維生素和其他必需的生長營養素。