In this study, all subjects will be given the necessary supplies and taught how to take care of their foot ulcer. Subjects who are randomly assigned to the gentamicin-collagen sponge treatment group will place a gentamicin-collagen sponge on their ulcer during daily wound care. Subjects who are randomly assigned to the oral levofloxacin treatment group will also perform daily wound care, but they will not be given the gentamicin-collagen sponge. Instead they will be given the antibiotic, levofloxacin to take by mouth during the treatment period.