Enrichment Broth (for EHEC Verotoxin ELISA)

Of the different human pathogenic variants of the intestine bacterium, Escherichia coli, one of the distinguishing features of EHEC bacteria is that they always produce so-called shigatoxins or verotoxins. Both names are used synonymously and refer to their high level of homology to shigellentoxin (the term Shiga-Like-Toxin is also commonly used) and their toxicity to verocells respectively. Such STEC / VTEC (shigatoxin-producing E. coli / verotoxin-producing E. coli) are now referred to as EHEC bacteria which trigger symptoms in humans and are therefore pathovars to humans. These again are classified into different serovars according to the antigenic structure. Some serovars are found more often among diseased patients than others. Furthermore, they do not all possess the same virulence markers, the main ones being intimin and enterohaemolysin beside the two shigatoxins Stx 1 and Stx 2. The information for producing the shigatoxin is located on a bacteriophage which is integrated in the bacterial chromosome. The amount of shigatoxin produced varies greatly between the different STEC strains. Screening for the presence of these toxins directly from the stool samples of patients with EHEC infection therefore cannot be recommended. The pathogens must first be enriched by culturing them from a patient stool sample in a suitable medium. The media which are suitable for this purpose are those which, in particular, activate the potential for producing shigatoxin as well as the selectivity factors for Escherichia coli. The ratio of EHEC organisms to the physiological, commensal E. coli intestinal flora is approximately 1 : 200. In this respect, an effective method of enrichment which induces the formation of shigatoxin is the basic requirement for successful screening in ELISA. This enrichment broth takes these requirements into consideration.