Aims: To examine the value of the DNase test as an alternative procedure for differentiating Corynebacterium diphtheriae from Corynebacterium-like colonies.
Methods and results: DNase test medium was inoculated by spotting a loopful of bacterial growth and incubated aerobically at 37 degrees C. The DNase production was detectable following both 24 and 48 h incubation periods. The DNase activity was detected in all 91 C. diphtheriae (37 toxigenic and 54 nontoxigenic) strains examined, previously identified by both conventional biochemical methods and API Coryne System. Conversely, DNase test results were negative in 93.9% of the 564 nondiphtherial Gram-positive rod clinical strains.
Conclusions: The DNase test emerged as an easily interpretable and cost-effective alternative screening procedure for C. diphtheriae laboratory identification.
Significance and impact of the study: The method should facilitate routine laboratory diagnosis of toxigenic and nontoxigenic C. diphtheriae.