Thermo Scientific™ MacConkey Agar with Sorbitol and MUG

Description

Selectively and differentially isolate sorbitol-negative Shiga toxin-producing Escherichia coli O157:H7 (STEC) with Thermo Scientific™ Remel™ MacConkey Agar with Sorbitol and MUG. MacConkeys Sorbitol Agar (SMAC) was introduced in 1986 as a primary platform for detection of STEC in stool specimens¹. MacConkeys agar with MUG was developed in 1984 by Trepeta and Edberg². In 1987, Krishnan et al. incorporated the 4-methylumbelliferyl-β-glucuronidase (MUG) test directly into SMAC agar to facilitate detection of STEC after 1 to 2 days of incubation³.

Shiga toxin-producing Escherichia coli (STEC) serotype O157:H7 is recognized as a cause of haemorrhagic colitis in 1982⁴, an illness characterized by bloody diarrhoea and severe abdominal pain, and haemolytic uraemic syndrome (HUS) and as such, is a significant human pathogen⁵. The pathogenesis of these diseases results from shiga toxin-producing serotypes of E.coli on routine isolation media. Effective culture methods require the use of sorbitol-containing medium to readily differentiate non-sorbitol fermenting STEC colonies from those of commensal strains of E.coli.

Selectively and differentially isolate sorbitol-negative Shiga toxin-producing E. coli O157:H7 (STEC) with MacConkey Agar with Sorbitol and MUG.

• Ease of differentiation: Among the other strains of E. coli, the enteropathogenic strain (STEC) lacks the sorbitol degrading ability within 48 hours of incubation. Moreover it does not synthesize the enzyme glucuronidase and hence there is no fluorescence production by this strain when MUG is present in the medium⁶.
• Selective: Bile salts inhibit gram positive organisms and crystal violet inhibits enterococci acting as selective agents.
• Recommended as a simple, inexpensive, rapid and reliable means of screening for E. coli O157 STEC.

This medium contains gelatin, casein and meat peptones that provides nitrogenous compounds and amino acids essential for bacterial growth. Bile salts inhibit gram positive organisms and crystal violet inhibits enterococci. D-sorbitol is fermented by commensal non-pathogenic strains of E. coli, producing pink colonies; STEC does not ferment sorbitol and produces clear or colorless colonies. The substrate MUG is hydrolyzed by most commensal E. coli strains but not by most strains of STEC. Most STEC strains ferment lactose but not D-sorbitol, allowing for differentiation between STEC strains and most fecal strains of sorbitol-positive E. coli.

Not all products are available for sale in all territories. Please inquire.

Remel™ and Oxoid™ products are now part of the Thermo Scientific brand.