Coagglutination for rapid testing of toxin producing Corynebacterium diphtheriae

Coagglutination test was standardised for rapid detection of diphtheria toxin after primary culture of C. diphtheriae isolates on conventional Loeffler's medium. The procedure was optimised with diphtheria toxoid (DT)-antidiphtheritic serum (ADS) system wherein Cowan-I strain of Staphylococcus aureus was sensitised with ADS. Toxoid in the range of 1.02 lf/ml to 4200 lf/ml could be detected by the present procedure. Toxin of C. diphtheriae could be demonstrated in five of eight clinical isolates, this correlated with the conventional guinea pig pathogenicity test. The coagglutination test thus needs further confirmation of its potential as a simple and satisfactory test for rapid detection of toxin-producing C. diphtheriae.