Summary
Several conventional methods have been described for the detection of Corynebacterium diphtheriae toxin, including Elek immunodiffusion, tissue culture using VERO cells and guinea pig inoculation. All these methods have the disadvantage of being either slow to complete or technically demanding, particularly when performed infrequently. We examined 64 strains of C. diphtheriae by PCR and Elek immunodiffusion, and strains showing a positive result in either assay were inoculated into guinea pigs. Seven isolates were positive in both Elek and PCR assays and subsequently positive in guinea pig inoculation assay. One isolate was negative in Elek testing but positive in PCR assay and guinea pig inoculation. All other isolates were negative in both Elek and PCR assays. The PCR assay is rapid with cycling and detection complete within 3–4 hrs of receipt of strains. PCR has now become the routine method for detection of C. diphtheriae toxin in our laboratory.