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

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.

Analysis of secreted protein profile and enzymatic activities from Corynebacterium diphtheriae and Bordetella pertussis on production batch media using peptide quenched fluorescent substrates.

Proteases were identified and characterized from the culture supernatant of the C. diphtheriae and B. pertussis bacteria. The proteases were secreted in the media and detected at the end of the exponential growth phase. Activity was detected in some fluorescent substrates, based on selected protein sequences such as insuline beta-chain, bradykinin, and synaptobrevin. The proteases were purified by means of gel filtration chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the purified proteins indicated, for the main secreted proteins, an estimated molecular mass of 30 kDa in C. diphtheriae and 69 kDa in B. pertussis culture media. The proteases were stable and presented enzymatic activity at 37 degrees C. These proteases were not related to the main toxic compounds described in these two bacteria, but could represent good markers for the fermentation process when the enzyme activity was measured with the fluorescent substrates.

Cell surface components and adhesion in Corynebacterium diphtheriae.

Main primary approaches and new developments in the study of the molecular basis of the adhesive process of Corynebacterium diphtheriae are reviewed along with a discussion of the potential importance of hemagglutinins, exposed sugar residues, hydrophobins and trans-sialidase enzymes as adhesins of strains of the sucrose fermenting and non-fermenting biotypes.

Trans-sialidase activity for sialic acid incorporation on Corynebacterium diphtheriae.

A rapid and sensitive assay for neuraminidase using peanut lectin hemagglutination was used to study the prevalence of neuraminidase activity among sucrose-fermenting and non-sucrose-fermenting toxigenic Corynebacterium diphtheriae strains. Neuraminidase activity was found in 15 (100%) isolates regardless of biotype, hemagglutinating activity and site of isolation of bacteria. Besides expressing the neuraminidase activity that hydrolyzes sialic acid from glycoconjugates, C. diphtheriae was also capable of transferring sialic acid residues from a sialyl-lactose donor. A single molecule probably expresses both neuraminidase and trans-sialidase activity. The trans-sialidase activity was documented by observations of the interactions of bacterial cells with wheat germ agglutinin and peanut lectins. C. diphtheriae expressed a trans-sialidase activity located on the cell surface that produced asialoglycoconjugates from a sialyl donor substrate and at the same time generated bacterial sialyl derivatives of beta-Gal acceptors.