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Chapter 52 : Corynebacterium diphtheriae and Clostridium tetani: Immune Response and Diagnostic Methods
Corynebacterium diphtheriae and Clostridium tetani are responsible for important diseases. Tetanus is caused by introduction of C. tetani from soil through contaminated wounds, while diphtheria results from airborne infection from infected cases. In both instances it is a potent exotoxin that is responsible for clinical disease. The toxin of C. tetani is so potent that the lethal dose may not be of sufficient strength to stimulate antibody production. In both instances formalin-inactivated toxins have been used for universal immunization. For children they are combined with pertussis vaccine, and adults are given both together at a reduced dose of diphtheria toxoid. The exotoxin produced by C. diphtheriae is the most important pathogenic factor. Although reliable methods of measuring antitoxic neutralizing antibodies have existed for many years for tetanus antitoxin, regular clinical laboratories rarely maintain the capability of determining tetanus antitoxin levels because they are of no use in diagnosis or treatment of the acute disease. The mouse neutralization assay is the most widely used, and this method is described in this chapter in detail. Injection of tetanus toxoid, which is one of the most effective immunizing agents in use today, regularly evokes antitoxic antibodies. There are few indications for the determination of tetanus antitoxin levels. The procedure for titration of tetanus antitoxin is based on the capacity of tetanus antitoxin to protect mice from death after subcutaneous injection of tetanus toxin.