A 65-year-old man presents with a chronic non-healing diabetic foot ulcer despite appropriate antibiotic therapy. A wound culture reveals polymicrobial flora, including Staphylococcus aureus and Pseudomonas aeruginosa. Which of the following is the most likely reason for the persistence of the infection?

• A. Resistance to multiple antibiotics
• B. Development of a biofilm on the wound surface
• C. Failure of the immune system to recognize the pathogens
• D. Lack of proper wound debridement