Fig. 2.

Analytic sensitivity of a DOT-ELISA to determine the cholera toxin in supernatants of Vibrio cholerae bacteria. Circles nitrocellulose membrane were coated with IgG anti-cholera toxin. After blocked with skimmed milk, a number de circles were incubated with the cholera toxin (0 to 0.1 mg/mL) and supernatants of no-toxin producing bacteria to create a dose–response curve. The reaction was developed with an anti-cholera toxin biotin conjugate and avidin-horseradish peroxidase The colour reaction was developed with 3,3′diaminobenzidine and a brown dot in the circle was considered as a positive reaction while, the colourless were considered as negative. Results of three different supernatants are show in a,b and c lines, while a supernatant without cholera toxin is show in d line