Diabetic Foot Infection

Definition

Diabetic foot infection (DFI) is an infection of the foot in patients with diabetes mellitus, often associated with neuropathy, peripheral vascular disease, and ulceration. It ranges from superficial cellulitis to deep tissue and bone involvement (osteomyelitis).

Epidemiology

• Common complication in patients with diabetes; lifetime risk of foot ulcer ~15–25%
• Higher incidence in older adults and those with long-standing diabetes
• Peripheral neuropathy and peripheral arterial disease are major risk factors
• More prevalent in low- and middle-income countries due to delayed access to care
• Leading cause of non-traumatic lower extremity amputation

Etiology

• Polymicrobial infection: Gram-positive cocci (Staphylococcus aureus, including MRSA), Gram-negative bacilli (E. coli, Pseudomonas), anaerobes in chronic or necrotic wounds
• Predisposing factors: neuropathy, ischemia, trauma, ulceration, poor glycemic control
• Skin barrier disruption allows bacterial invasion
• Biofilm formation contributes to chronicity and antibiotic resistance

Pathophysiology

• Peripheral neuropathy leads to loss of protective sensation and abnormal foot mechanics, causing ulceration
• Peripheral arterial disease reduces tissue perfusion, impairing healing and immune response
• Bacterial colonization of ulcerated tissue triggers local inflammation and tissue destruction
• Deep infection may extend to fascia, muscle, and bone, leading to osteomyelitis
• Immune dysfunction in diabetes exacerbates infection severity