ANTIBODY-CAPTURE ELISA FOR THE SENSITIVE DIRECT-DETECTION OF HEAT-STABLE TOXIN OF ESCHERICHIA-COLI FROM SOFT CHEESE

On the background of the EU Milk Hygiene Directive 92/46 a simple, sen sitive and specific ELISA for the detection of heat-stable Escherichia coli toxin (ETEC-ST) was developed. The principle is a competitive an tibody capture test. For immunizing rabbits a commercially available t oxin (STa, SIGMA) was used. The test allows to detect within a few hou rs the toxin from a culture supernatant in a sensitivity of 1 ng/ml - qualitatively and quantitatively, The at random isolation and further handling of suspicious colonies from a selective medium normally is ve ry laborious. Therefore, an additional method was developed by incubat ing the sample, e.g. 10 g of cheese in the selective EE-broth which is subcultured and incubated again in Caye 2 broth for enhancing the tox in production where from the toxin can be identified. Even al a contam ination flora of more than 10(5) coliforms/g and 10(1) E.coli/g yet 7 toxin producing E.coli/g in the original flora could be detected. This method enables a large saving of material and time and, additionally, it is more reliable to detect toxin producers in a sample than the at random isolation of suspicious colonies.