[Catalase-negative Rothia dentocariosa: evaluation of additional descriptive tests]

Rothia dentocariosa is one of the human oral flora members, and classified in the group of coryneform bacteria which are taxonomically heterogeneous. Although R. dentocariosa is considered as a contaminant in throat cultures generally, it may be the causative infectious agent in the presence of predisposing factors. The catalase activity which is used as a simple and initial identification test, becomes contradictory because of the detection of the catalase negative strains recently. The aim of this study was to compare several biochemical and enzymatic reactions for the identification of catalase positive and negative R. dentocariosa strains. A total of 42 R. dentocariosa strains which were isolated from throat cultures have been studied, and the positivity rate of mannose fermentation in catalase negative R. dentocariosa isolates was found to be significantly higher than those catalase positive (p < 0.05). In conclusion, mannose fermentation test seems to be a useful tool as an additional identification method of catalase negative R. dentocariosa isolates.