Growth interaction between Candida albicans and Streptococcus salivarius: in vitro and in vivo studies

Suppression of Candida albicans in the mouth by oral flora has been proposed as one of the mechanisms preventing candidal overgrowth. According to Liljemark and Gibbons (1973), Streptococcus salivarius plays a significant role in this process. The aim of this investigation was to study the growth interaction between C. albicans and S. salivarius in vitro and in vivo. An aerobic continuous-flow system was used for the in vitro study. Pure and mixed cultures of C. albicans (NCPF 3118) and S. salivarius (NCTC 8618) were inoculated into a buffered medium containing either 0.1 per cent or 0.001 per cent glucose concentrations and incubated at 37 degrees C for 55 hours. Two in vivo investigations were undertaken using inbred germfree C3H mice. In the first, mice were exposed to a mixed suspension of S. salivarius and C. albicans for 48 hours. In the second the mice were exposed to S. salivarius for 48 hours. Fourteen days later they were contaminated with C. albicans. A comparison of growth curves showed no growth inhibition between the species. The in vivo studies showed that oral lesions from candidal infestation occurred in all mice. We were therefore unable to demonstrate in vitro or in vivo suppression of C. albicans in the presence of S. salivarius.