The effect of nondialyzable material (NDM) cranberry extract on formation of contact lens biofilm by Staphylococcus epidermidis

Purpose. To assess the effects of NDM from cranberries on Staphylococcus epidermidis biofilm formed on soft contact lenses. Methods. Soft contact lenses were incubated in Tryptic Soy Broth (TSB) together with S. epidermidis (ATCC35984/RP62A) and various concentrations of NDM, and inspected by scanning electron and confocal microscopy. The TSB was collected after sonification and monitored turbidometrically. Results. NDM at ≥500 μg/mL concentration caused a significant (P < 0.01) reduction of biofilm. Scanning electron microscopy of biofilm in the presence of 500 to 1000 μg/mL NDM confirmed these results. In control lenses, multilayered mushroom-shaped biofilm and complete coverage of the lens surface were seen, whereas after incubation with 500 μg NDM per mL TSB, the biofilm was thinner with smaller protuberances, and exposed lens surface was partially seen. In samples incubated with 1000 μg NDM per mL TSB, the lens surface was clearly seen between sporadic microcolonies. Conclusions. NDM reduces formation of biofilm on soft contact lenses. This has important implications for the prevention of contact lens-related corneal infections caused by S. epidermidis.