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Harlequin SMAC-BCIG

Product Code: HAL006

A specific substrate chromogenic medium for the isolation of Escherichia coli O157:H7. Based on the formulation of Sorbitol MacConkey Agar (SMAC), Harlequin SMAC-BCIG includes the chromogenic substrate BCIG for improved specificity.

Application(s): Industrial, Food, Clinical
Organism(s): E.coli

This is a specific substrate medium for the isolation of Escherichia coli O157:H7, the primary serovar associated with haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS). Pathogenicity of the organism is linked to the production of verocytotoxins (VT1 and VT2), but it should be noted that not all strains of O157 produce verocytotoxins, and that strains from other serovars can be toxin producers (e.g. O26, O103, O111, O113, O145).  E.coli O157 has been associated epidemiologically with food poisoning outbreaks involving beef burgers and cold cooked meats.

This medium is a modification of Sorbitol MacConkey Agar (SMAC). The addition of the chromogenic substrate BCIG (5-bromo-4-chloro-3-indoxyl-β-D-glucuronide) improves the specificty of the medium.

E.coli O157:H7 is typically sorbitol negative and Î²-glucuronidase negative producing pale translucent colonies on this medium.

The majority of other E.coli strains are Î²-glucuronidase positive and sorbitol positive (pink/red colonies). 

A small percentage of E.coli are Î²-glucuronidase positive and sorbitol negative and thus appear as blue/green colonies on this medium.

Consequently this medium can distinguish between non-O157 sorbitol negative E.coli and the genuine toxigenic E.coli O157:H7.  This reduces the number of unnecessary confirmation tests that are performed.  The medium can be made more selective by the addition of Cefixime Tellurite supplement X161 to prepare CT-SMAC. Most workers recommend the use of CT-supplemented medium alongside unsupplemented medium to ensure maximum isolation of E.coli O157. This medium can also be useful for the detection of other VTEC producing E.coli in conjunction with specifically targetted IMS particles (Captivate^TM).