HiMedia – M1574A_HiCrome™ EC 0157 H7 Agar Modified

Principle and Interpretation
Escherichia coli O157:H7 belongs to the Enterohemorrhagic Escherichia coli (EHEC) group and it predominates as a food borne pathogen. E. coli O157: H7 was first recognized as a human pathogen in 1982 when two outbreaks of hemorrhagic colitis were associated with consumption of undercooked ground beef that has been contaminated with this organism (1). HiCrome™ EC O157:H7 Agar, Modified is a chromogenic medium recommended for the isolation and differentiation of E. coli O157:H7 from food and environmental samples. HiCrome™ ECO157:H7 Agar, Modified is based on the formulation described by Rappaport and Henigh (2). The medium contains sorbitol and a proprietary chromogenic mixture instead of lactose and indicator dyes respectively, as is conventionally used. The chromogenic substrate is specifically and selectively cleaved by E. coli O157: H7 resulting in a dark purple to magenta coloured moiety. E. coli gives bluish green coloured colonies. Tryptone and yeast extract provides carbonaceous, nitrogenous and growth nutrients. Bile salts mixture and SLS inhibits gram-positive organisms. Potassium tellurite selects the serogroups and inhibits Aeromonas species and Providencia species.

原理與解釋
大腸桿菌O157：H7屬於腸出血性大腸桿菌（EHEC）組，並且它主要作為食源性病原體。大腸桿菌O157：H7在1982年首次被認為是人類病原體，當時兩次爆發的出血性結腸炎與食用已被該生物體污染的未煮熟的碎牛肉有關（1）。 HiCrome™EC O157：H7 Agar，Modified是一種顯色培養基，推薦用於從食品和環境樣品中分離和分離大腸桿菌O157：H7。 HiCrome™ECO157：H7瓊脂，改性基於Rappaport和Henigh（2）描述的配方。該培養基含有山梨糖醇和專有的生色混合物，分別代替乳糖和指示劑染料，如常規使用的那樣。顯色底物被大腸桿菌O157：H7特異性和選擇性地切割，產生深紫色至品紅色部分。大腸桿菌產生藍綠色的菌落。 胰蛋白腖和酵母提取物提供碳質，含氮和生長營養素。膽汁鹽混合物和SLS抑制革蘭氏陽性生物。亞碲酸鉀選擇血清群並抑制氣單胞菌屬和普羅威登斯菌種。