Harlequin® Sorbitol MacConkey Agar (SMAC)

Item No.  NCM1007A

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Sorbitol MacConkey Agar (SMAC) is for the isolation of Escherichia coli O157:H7 and is not intended for use in the diagnosis of disease or other conditions in humans. Pathogenicity of Escherichia coli O157:H7, the primary serovar associated with haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS), is linked to the production of verocytotoxins (VT1 and VT2). However, 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-ß-D-glucuronide) improves the specificity of the medium. E. coli O157:H7 is typically sorbitol negative and ß-glucuronidase negative producing pale translucent colonies on this medium. The majority of other E. coli strains are ß-glucuronidase positive and sorbitol positive (pink/red colonies). A small percentage of E. coli are ß-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 targeted IMS beads (Captivate™).  
Analyte E. coli O157:H7
Brand NEOGEN® Culture Media
Formula Liter
Peptone 20.0 g/L
Sorbitol 10.0 g/L
Bile Salt No.3 1.5 g/L
Sodium Chloride 5.0 g/L
BCIG 0.1 g/L
Neutral Red 0.03 g/L
Crystal Violet 0.001 g/L
Agar 12.0 g/L
Grams per Litre 48.60
Litres per 500g 10.00
Mass 500 g
Package Dimensions 4.60 IN x 2.90 IN x 8.60 IN
Package Weight 1.35 LB
Plates per 500g 560.00
  1. Suspend 48.6 grams of the medium in one liter of purified water.
  2. Heat with frequent agitation and boil for one minute to completely dissolve the medium.
  3. Autoclave at 121°C for 15 minutes.
  4. Cool to 45-50°C, add 2 vials of NCM4045-0.5* Cefixime Tellurite, each reconstituted using 5mL of sterile deionized/RO water, and pour plates.

*Larger vials may be available. Please see appropriate supplement data sheet for availability and preparation instructions.

Previous Item Number Product was previously known as LabM Product: HAL006 Harlequin™ SMAC-BCIG



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