HiMedia - M298-5KG - MacConkey Sorbitol Agar Base is recommended as the selective medium for isolation and detection of Escherichia coli O157 : H7 from food and animal feeding stuffs. Pack size is 5KG

ITEM #: 6294611
MacConkey Sorbitol Agar is based on the formulation described by Rappaport and Henigh (1). This medium is recommended for isolation of enteropathogenic Escherichia coli O157: H7, which ferments lactose but does not ferment sorbitol, hence produces colourless colonies. This organism has been recognized as a cause of hemorrhagic colitis (2). E.coli O157: H7 is a human pathogen associated with hemorrhagic colitis that results from the action of a shiga-like to x in (SLT) (5, 6).
MacConkey Sorbitol Agar however should not be solely used to detect pathogenic E.coli O157: H7 strains as some nonto x ic strains will also not ferment sorbitol (4).
On standard MacConkey Agar containing lactose, this strain is indistinguishable from other lactose-fermenting E.coli . In MacConkey Sorbitol Agar Base, lactose is replaced by sorbitol. Unlike most E.coli strains, E.coli O157:H7 ferments sorbitol slowly or not at all (3, 8). The growth of E.coli O157:H7 on MacConkey Agar with Sorbitol shows colourless colonies and most of the fecal flora ferment sorbitol and appear pink. MacConkey Agar with Sorbitol therefore permits ready recognition of E.coli O157:H7 (5, 6, 7).
Peptic digest of animal tissue and proteose peptone supply necessary nutrients like nitrogenous and carbonaceous compounds, minerals, vitamins and trace ingredients for the growth of organisms. Crystal violet and bile salt mi x ture present in the medium inhibit growth of gram-positive bacteria. Sodium chloride maintains osmotic equilibrium. Neutral red is an indicator. D-Sorbitol is the fermentable carbohydrate.
Directions:
Suspend 50.03 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. AVOID OVERHEATING. Cool to 45-50°C and pour into sterile Petri plates.
MacConkey Sorbitol Agar Base is recommended as the selective medium for isolation and detection of Escherichia coli O157 : H7 from food and animal feeding stuffs. Pack size is 5KG
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