Objective: To evaluate the mechanisms of microbial interaction between the oral pathogens Candida albicans and Streptococcus mutans.
Materials and methods: Growth kinetics for the two micro-organisms, cultured individually or together, were followed experimentally for 36 h. The different growth curves were analysed by means of mathematical modelling.
Results: Under the experimental conditions, S. mutans final concentration, when grown individually, was 5-times that of C. albicans. Contrarily, when both micro-organisms grew together, this ratio was inversed and C. albicans final concentration was even higher than that of S. mutans. When both micro-organisms share the niche, a model including linear competition among one another was best suited to reproduce the experimental observations. The results of this model show that the initial growth rates of both species are positively influenced by their mutual interaction. However, at longer incubation times, C. albicans prevents bacterial growth and achieves concentrations 4-times higher than when grown individually.
Conclusions: The results suggest that C. albicans biofilm formation could be potentiated by the presence of S. mutans by two mechanisms: synergically at short times and by competition at longer periods.