Controlling Streptococcus mutans and Staphylococcus aureus biofilms with direct current and chlorhexidine

Microbial biofilms formed on biomaterials are major causes of chronic infections. Among them, Gram-positive bacteria Streptococcus mutans and Staphylococcus aureus are important pathogens causing infections associated with dental caries (tooth-decay) and other medical implants. Unfortunately, current antimicrobial approaches are ineffective in disrupting established biofilms and new methods are needed to improve the efficacy. In this study, we report that the biofilm cells of S. mutans and S. aureus can be effectively killed by low-level direct current (DC) and through synergy in concurrent treatment with DC and chlorhexidine (CHX) at low concentrations. For example, after treatment with 28 µA/cm² DC and 50 µg/mL CHX for 1 h, the viability of biofilm cells was reduced by approximately 4 and 5 logs for S. mutans and S. aureus, respectively. These results are useful for developing more effective approaches to control pathogenic biofilms.