A PCR for dtxR gene: application to diagnosis of non-toxigenic and toxigenic Corynebacterium diphtheriae.

The significant rise in the percentage of adults susceptible to diphtheria and the emergence of non-toxigenic Corynebacterium diphtheriae strains as the causative agent of endocarditis and other systemic infections emphasize the need for alternative laboratory diagnostic procedures. In this study, for the first time, the value of a species-specific PCR assay that targets the dtxR gene is documented as a procedure for differentiating C. diphtheriae from Corynebacterium-like colonies. The results of the PCR-dtxR were all positive for 91 C. diphtheriae (54 non-toxigenic and 37 toxigenic) strains. PCR-dtxR completely correlated with the standard biochemical and commercial identification for all C. diphtheriae strains tested. Conversely, the PCR-dtxR results were negative in 100% of the 111 non-diphtherial Gram-positive rod strains obtained during identification procedures in a hospital laboratory. Thus, the PCR-dtxR assay emerged as viable, cost-effective screening method for C. diphtheriae laboratory identification.