HiMedia – M1682 HiCrome™ Vibrio Agar

Principle and Interpretation
Vibrio’s have played a significant role in human history. Outbreaks of cholera, caused by Vibrio cholerae, can be traced back in time to early recorded descriptions of enteric infections. The Vibrios have also received the attention of marine microbiologists who observed that the readily cultured bacterial population in near-shore waters and those associated with fish and shell fish were predominantly Vibrio species(4). Vibrio species are mainly responsible for causing cholera and food poisoning in humans. Vibrio cholerae causes cholerae due to the intake of contaminated food such as raw oysters. Vibrio parahaemolyticus is a major cause of food borne infections, causing food poisoning (1). Since Vibrio species naturally occur in sea-water, worth special mention is their need for sodium chloride, although some species can grow with minimum sodium chloride concentration (4). The widely used media for Vibrio isolation are TCBS Agar and Alkaline Peptone Water (2). However accompanying sucrose-fermenting bacteria pose a problem in the identification of Vibrio species on TCBS Agar. On HiCrome™ Vibrio Agar, the colour development by Vibrio species is not affected by the presence of colonies of other bacteria. This is because, the amount of colour developed depends on the reaction of the bacterial beta-galactosidase with the substrate contained in the media (3). Peptone provides carbonaceous and nitrogeneous compounds, long chain amino acids and essential nutrients to the organisms. High concentration of sodium chloride in addition to maintaining the osmotic equilibrium also has an inhibitory action on the accompanying microflora. Sodium thiosulphate, sodium citrate and sodium cholate are used in the formulation because they can inhibit the growth of gram positive and some gram negative bacteria, but not members of Enterobacteriaceae. The proprietary chromogenic mixture incorporated in the medium helps in the chromogenic differentiation of Vibrio cholerae and Vibrio parahaemolyticus. The high (alkaline) pH of the medium helps in selective isolation of Vibrio species.

原理與解釋
弧菌在人類歷史上發揮了重要作用。由霍亂弧菌引起的霍亂爆發可追溯到早期記錄的腸道感染描述。 Vibrios也受到海洋微生物學家的關注，他們觀察到近岸水域中易於培養的細菌群體以及與魚類和貝類相關的細菌群體主要是弧菌（4）。弧菌物種主要是造成人類霍亂和食物中毒的原因。由於攝入生牡蠣等污染食物，霍亂弧菌會引起霍亂。副溶血性弧菌是食源性感染的主要原因，導致食物中毒（1）。由於弧菌物種天然存在於海水中，值得特別提及的是它們對氯化鈉的需求，儘管有些物種可以以最低的氯化鈉濃度生長（4）。廣泛使用的弧菌分離培養基是TCBS瓊脂和鹼性蛋白腖水（2）。然而伴隨的蔗糖發酵細菌在鑑定TCBS瓊脂上的弧菌物種方面存在問題。在HiCrome™Vibrio瓊脂上，弧菌物種的顏色發展不受其他細菌菌落的影響。這是因為，顯色的顏色取決於細菌β-半乳糖苷酶與培養基中所含底物的反應（3）。 蛋白腖為生物體提供碳質和硝基化合物，長鏈氨基酸和必需營養素。除了維持滲透平衡之外，高濃度的氯化鈉還對伴隨的微生物群具有抑製作用。硫代硫酸鈉，檸檬酸鈉和膽酸鈉 因為它們可以抑制革蘭氏陽性菌和一些革蘭氏陰性菌的生長，但不能抑制腸桿菌科的成員。摻入培養基中的專有顯色混合物有助於霍亂弧菌和副溶血性弧菌的顯色分化。培養基的高（鹼）pH有助於選擇性分離弧菌。