MacCONKEY SORBITOL AGAR BASE W/ RHAMNOSE

Description

E. coli O157:H7 is a human pathogen associated with hemorrhagic colitis that results from the action of a shiga-like toxin. MacConkey agars are selective media and recommended as differential plating media for detection and isolation of coliforms from various samples clinical, dairy, food, water, pharmaceuticals etc. Of different E. coli strains, E. coli O157:H7 which is a hemorrhagic strain does not ferment sorbitol or rhamnose. This biochemical feature aids in differentiating E. coli O157:H7 from other E. coli strains. Generally, on standard MacConkey Agar medium containing lactose, this strain cannot be differentiated from other lactose fermenting E. coli. Rhamnose is often fermented by most sorbitol negative Escherichia coli of other serogroups. MacConkey Sorbitol Agar Base w/ Rhamnose contains two sugars as sorbitol and rhamnose. Since E. coli O157:H7 do not usually ferment sorbitol or rhamnose it appears as colourless to straw coloured colonies. While rhamnose positive and sorbitol negative appear as pink or red coloured colony and it should not be counted as presumptive Escherichia coli O157:H7