Integral Supplement to E. coli O157 Isolation

The current UK outbreaks of Escherichia coli 0157 infection in young children have once again highlighted the seriousness of the ensuing illness, the importance of timely diagnosis and the need to track the source of infection. Enrichment of samples is an important part of the E. coli 0157 recovery and isolation process and Lab M’s Buffered Peptone Water is used with VCC Selective Supplement to prepare a pre-enrichment broth for organism recovery. It then also serves as a selective enrichment medium for the isolation of E. coli O157 from food and other samples.

As well as this enrichment broth, Lab M provides a full range of media for E. coli O157 culture, including modified Tryptone Soy Broth (mTSB), Sorbitol MacConkey Agar (SMAC) and Cefixime Tellurite MacConkey Agar (CT-SMAC), selective differential media for the isolation of E. coli O157:H7, the primary serovar associated with haemorrhagic colitis and haemolytic uraemic syndrome. Harlequin™ SMAC-BCIG is a modification of SMAC agar in which the addition of a specific chromogenic substrate (5-bromo-4-chloro-3-indoxyl-β-Dglucuronide [BCIG]) allows the straightforward differentiation of E. coli O157:H7 from other strains on the basis of colony colour.

Alongside these media is Rhamnose MacConkey (VTEC O26) Agar, selective for verocytotoxin producing E.coli O26, a strain that is also associated with haemorrhagic colitis and haemolytic uraemic syndrome. This medium is based on MacConkey agar, but substitutes rhamnose for the usual lactose as the fermentable carbohydrate. VTEC O26 colonies are unable to ferment the rhamnose present in the medium so remain translucent. All other non-O26 VTEC colonies appear as pink to red.