[Antibacterial immunity in diphtheria. Experimental research].

A number of 700 guinea pigs were immunized by parenteral route with non-toxigenic Corynebacterium diphtheriae strains, then inoculated with various doses of homologous and heterologous toxigenic C. diphitheriae strains. The results showed that non-toxigenic C. diphtheriae strains confer a certain degree of protection when the challenge is done with homologous toxigenous strains, especially when not more than 500 million germs/ml are used for the challenge dose. This suggests that the carriage of non-toxigenic diphtheriae bacilli is a useful phenomenon for maintaining an immune balance in diphtheria in the present epidemiological context, and that their sterilization is not opportune.