CHROMagar O157

For isolation from specimens of enterohaemorrhagic E.coli O157, allowing their direct differentiation

Using CHROMagar O157, a species specific chromogenic medium for E.coli O157 applying procedures identical to those used in classical methods:

• Prepare CHROMagar O157 petri plates according to instructions
• Choose a resuscitation method and an enrichment method such as immunocapture on specific beads
• Innoculate the enriched suspension
• Incubate overnight

Rapid and reliable detection of the enterohaemorrhagic E.coli O157. Easily distinguishable colonies due to the purple colouring they have aquired. Most other bacterial species are inhibited, giving blue or colourles colonies. Despite specifity is improved in comparison to Sorbitol MacConkey Agar, when direct isolation method is used, the false positive must be screened out by additional tests and candidates must be further studied for confirmation. Purple colonies of E.coli O157 can be studied directly with indole test and by serogrouping.

Results can be viewed under normal lighting

• E.coli O157 - purple
• other bacterial colonies - inhibited, blue or colourless