DNase test as a novel approach for the routine screening of Corynebacterium diphtheriae

Abstract

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°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.

Detection Methods for Laboratory Diagnosis of Diphtheria

“…As alternative screening test for differentiating C. diphtheriae from Corynebacterium-like colonies the DNAse test was proposed (Pimenta et al 2008b). After incubation of colonies inoculated on DNAse-test media for 24 to 48 h, all 91 tested C. diphtheriae isolates (toxigenic and non-toxigenic) showed DNAse activity, while 93.9 % of 564 nondiphtherial Corynebacterium strains (including 3 C. pseudotuberculosis isolates) yielded negative results.…”

Clonal multidrug-resistant Corynebacterium striatum within a nosocomial environment, Rio de Janeiro, Brazil

“…Other clinical specimens were inoculated onto a Columbia agar base with the addition of 5% sheep's blood and incubated at 37ºC in a 3-5% CO 2 atmosphere and monitored for 72 h (Camello et al 2003). Positive bacterial cultures for irregular Gram-positive rods were preliminarily characterised by colonial morphology, pigmentation, haemolysis, DNase activity and CAMP reaction with Staphylococcus aureus (Camello et al 2003, Funke & Bernard 2007, Pimenta et al 2008. Phenotypic characterisation was also performed using the semi-automated API Coryne System 3.0 (bioMérieux) with the API web decoding system (apiweb.biomerieux.com) (Almuzara et al 2006, Funke & Bernard 2007, Campanile et al 2009).…”

A new, simple, rapid test for detection of DNase activity of microorganisms: DNase Tube test

“…and M. catarrhalis (Elston and Elston, 1968;Fusillo and Weiss, 1959;MacFaddin, 2000). A short set of routine tests, which includes DNase as a major differentiating factor, would be especially useful as a screening of microorganisms including Corynebacterium species (Pimenta et al, 2008). We showed that it is possible to differentiate S. marcescens from E. aerogenes in as short as half an hour using the DTT.…”

“…The major drawback of these tests in addition to problems mentioned is the necessity of a long time to see the results of DNase activity of the bacteria. Defi ning the DNase activity of S. aureus or Corynebacterium takes 24 to 48 h using the DNase agar test (Pimenta et al, 2008). Here we developed a simple, rapid and inexpensive method to illustrate DNase activity of any microorganism that can grow in any broth medium.…”