Sucrose-mediated formation and adhesion strength of Streptococcus mutans biofilms on titanium

Abstract

Biofilms consist of bacterial cells surrounded by a matrix of extracellular polymeric substance (EPS), which protects the colony from many countermeasures, including antibiotic treatments. Biofilm EPS composition is affected by environmental factors. In the oral cavity, the presence of sucrose affects the growth of Streptococcus mutans that produce acids, eroding enamel and forming dental caries. Biofilm formation on dental implants commonly leads to severe infections and failure of the implant. This work determines the effect of sucrose concentration on biofilm EPS formation and adhesion of Streptococcus mutans, a common oral colonizer. Bacterial biofilms are grown with varying concentrations of sucrose on titanium substrates simulating dental implant material. Strategies for measuring adhesion for films such as peel tests are inadequate for biofilms, which have low cohesive strength and will fall apart when tensile loading is applied directly. The laser spallation technique is used to apply stress wave loading to the biofilm, causing the biofilm to delaminate at a critical tensile stress threshold. Biofilm formation and EPS structures are visualized at high magnification with scanning electron microscopy (SEM). Biofilm substrate coverage and adhesion strength of biofilms initially increase with increasing sucrose concentration, but then decrease as sucrose concentration continues to increase. For biofilms grown with non-zero concentrations of sucrose, S. mutans adhesion to the substrate is higher than the adhesion of osteoblast-like cells to the same substrates. These results suggest sucrose-mediated adhesion and formation on titanium of S. mutans biofilms may outcompete osteoblasts during osseointegration, which could explain higher rates of peri-implant disease associated with high sugar diets.