DIPHTHERIA VIRULENCE AGAR BASE

Corynebacterium diphtheriae is a principle human pathogen and owes its pathogenicity to the production of a potent exotoxin active on a variety of tissue including heart muscles and peripheral nerves. Toxin diffusing from a streak culture of suspected C. diphtheriae is demonstrated by the formation of a white line of precipitate where it meets with diphtheria antitoxin diffusing from a strip of filter paper embedded in the agar. In vitro toxigenicity (virulence) of C. diphtheriae was first described by Elek. Eleks technique was further improved by King, Frobisher and Parsons by the use of a standardized medium. This medium gave results comparable with animal inoculation test. Also it was found that proteose peptone supported toxin production in addition to maintaining the consistency of results. Hermann et al developed a non-serum based enrichment to overcome the irregularities encountered during the usage of horse, sheep or rabbit serum based enrichments. These non-sera based enrichments consist of Acicase, tween 80 and glycerol. Upon incubation of the inoculated plate, a line of precipitin is observed for toxigenic strains.

for determination of toxigenicity of Corynebacterium diphtheriae