Rapid GM1-enzyme-linked immunosorbent assay with visual reading for identification of Escherichia coli heat-labile enterotoxin

A modified, quicker and simpler GM1-enzyme-linked immunosorbent assay procedure for detection of Escherichia coli heat-labile enterotoxin (LT) has been developed with the intent that it should be useful in less well-equipped laboratories. The method, which makes use of stable reagents including commercially available horseradish peroxidase immunoglobulin conjugate, can detect LT in overnight cultures within 1 working day (8 h), and the tests can be read with the naked eye. This GM1-horseradish peroxidase-enzyme-linked immunosorbent assay shows excellent quantitative and qualitative correlation with the conventional GM1-enzyme-linked immunosorbent assay. When 100 human E. coli strains were analyzed blindly and in parallel by the two methods, LT production was identified in 50 out of 50 LT-positive strains and in 0 out of 50 LT-negative strains by either method.