Introduction: An important virulence factor of Enterococcus faecalis is its ability to form biofilms. Most studies on biofilm formation have been carried out by using E. faecalis monocultures. Given the polymicrobial nature of root canal infections, it is important to understand biofilm formation of E. faecalis in the presence of other microorganisms.
Methods: Eight clinical strains of E. faecalis were tested for biofilm formation on hydroxyapatite disks in the presence and absence of a Streptococcus mutans biofilm.
Results: Significantly more E. faecalis viable cells were found in biofilms in the presence of S. mutans. This phenomenon was, however, strain-dependent. Of the 8 strains tested, biofilm formation of strains AA-OR34, ER5/1, and V583 was not influenced by S. mutans biofilms.
Conclusions: The results from this study, especially the strain difference, underline the importance of studying biofilm formation in a more realistic multispecies setting.