HiMedia – M1931 HiCrome™ Staph Selective Agar

Principle and Interpretation
Staphylococci are widespread in nature, though they are mainly found living on the skin, skin glands and mucous membranes of mammals and birds. Humans and animals are the primary source of this organism. Because of its widespread nature it is easily transferred to food and a cause of food poisoning if not handled properly.(1) The coagulase positive species S. aureus is well documented as a human opportunistic pathogen. Staphylococcus species are a major cause of food poisoning and produces a wide variety of enterotoxins, thus causing various types of disease symptoms. The ability to clot plasma continues to be the most widely used and accepted criterion for the identification of pathogenic staphylococci associated with acute infections (2). This medium is a selective chromogenic medium recommended for the isolation and enumeration of coagulase positive staphylococci in foods within 24 hours. Peptone special in the medium supplies the essential nitrogeneous, carbonaceous required for the growth. Phenol red is pH indicator. Mannitol in the medium is fermented by Staphylococcus aureus and the chromogenic mixture incorporated in the medium is specifically cleaved by Staphylococcus aureus to give greenish coloured colonies which are easily distinguishable. Staphylococcus epidermidis does not ferment mannitol hence blue coloured colonies are observed. Sodium chloride in the medium helps to maintain the osmotic equilibrium of the medium. High concentration of sodium chloride also helps in inhibiting the accompanying microflora.

原理與解釋
葡萄球菌在自然界中廣泛存在，儘管它們主要存在於哺乳動物和鳥類的皮膚，皮膚腺和粘膜上。人類和動物是這種生物的主要來源。由於其廣泛的性質，如果處理不當，很容易轉移到食物和食物中毒的原因。（1） 凝固酶陽性物種金黃色葡萄球菌被充分記錄為人類機會致病菌。金黃色葡萄球菌是食物中毒的主要原因並且產生多種腸毒素，因此引起各種類型的疾病症狀。血漿凝塊的能力仍然是最廣泛使用和接受的鑑定與急性感染相關的致病性葡萄球菌的標準（2）。 該培養基是一種選擇性顯色培養基，推薦用於在24小時內分離和計數食品中凝固酶陽性葡萄球菌。特殊的蛋白腖在培養基中提供生長所需的必需的氮，碳質。酚紅是pH指示劑。培養基中的甘露醇由金黃色葡萄球菌發酵，並且摻入培養基中的生色混合物被金黃色葡萄球菌特異性裂解，得到綠色的菌落，其易於區分。表皮葡萄球菌不發酵甘露醇，因此觀察到藍色菌落。培養基中的氯化鈉有助於維持培養基的滲透平衡。高濃度的氯化鈉也有助於抑制伴隨的微生物群落。