Methods: NDM was obtained by extensive dialysis of cranberry juice followed by lyophilization. Effect of NDM on bacteria detachment from biofilms: Biofilm consisting of radioactively labeled S. sobrinus, glucosyltransferase/fructosyltransferase (GTF/FTF) and saliva was constructed on hydroxyapatite beads. NDM at various concentrations (0-1.33 mg/ml) was added to the biofilm in the presence or absence of sucrose. The ability of NDM to desorb bacteria from biofilm was estimated by determining the amount of bacteria on HA beads. Effect of NDM on biofilm construction and thickness: Biofilm formed in a constant-depth film fermenter (CDFF)was incubated with 2 or 4 mg/ml NDM. In other experiment biofilm was constructed in CDFF from bacteria pre-incubated with 2 mg/ml NDM.In both studies biofilms were stained with propidium iodide and biofilm depth was monitored by confocal laser scanning microscope.
Results: NDM (0.066 mg/ml) caused desorption of more than 50 % (p<0.05) of the bacteria from biofilms in the absence of sucrose while, lesser effect was observed in the presence of the sugar. Increased concentration of NDM reduced bacterial density and depth in the formed biofilm, as well as in biofilms, constructed by bacteria pre-exposed to NDM.
Conclusion: NDM affects biofilm formation. Its effect is more pronounced in non sucrose-dependent adhesion where the bacteria form the biofilm via hydrophobic, electrostatic, or protein interactions.