Diabetic Foot Infections

Source: Fish DN, Pendland SL, Danziger LH. Skin and Soft-Tissue Infections. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. http://accesspharmacy.com/content.aspx?aid=8002378. Accessed July 21, 2012.

• Foot infections in patients with diabetes
• Three types:
  • Deep abscesses
  • Cellulitis of the dorsum
  • Mal perforans ulcers

• Begins with local bacterial invasion and is polymicrobic (average of 2.3–5.8 isolates per culture).
  • Most common pathogens: Staphylococci (especially S. aureus) and streptococci
  • Gram-negative bacilli and anaerobes occur in 50% of cases.

• Key factors in development of diabetic foot problems (may occur in isolation or together):
  • Neuropathy
  • Angiopathy and ischemia
  • Immunologic defects that impair wound healing

• One of most common diabetes complications, responsible for up to 20% of all hospitalizations of diabetics.

• Optimize blood glucose control.
• Encourage daily patient self-examination of feet.
• Examine feet at every physician visit.

• Uncontrolled blood glucose
• Peripheral neuropathy

• Infections often more extensive than they initially appear.
• Clinical signs of infection may not be present secondary to angiopathy and neuropathy.

Signs and Symptoms

• Swelling or erythema in foot (patient unaware of pain due to peripheral neuropathy)
• Warmth
• Presence of pus
• Draining sinuses
• Pain
• Tenderness
• Temperature: normal or mildly elevated
• Lesions vary in size when present.
• Four-smelling odor suggests anaerobic organisms.

Means of Confirmation and Diagnosis

• Culture results

Laboratory Tests

• Culture and sensitivities
  • Obtain specimen from deep culture, preferably expressed pus from wound base.
  • Culture for aerobic and anaerobic organisms.

Imaging

• Assess for osteomyelitis via radiograph, bone scan, or both, as appropriate

Diagnostic Procedures

• Surgical debridement to obtain samples for culture and sensitivities

Differential Diagnosis

• Cellulitis
• Gout
• Septic arthritis

• Preserve as much normal limb function as possible.
• Prevent infectious complications.

• Most infections successfully treated on outpatient basis with wound care and antibiotics.
• Maximize glycemic control to ensure optimal wound healing.

• Thoroughly debride necrotic tissue, with wound drainage and amputation as required.
• Wounds must be kept clean and dressings changed 2–3 times daily.
• Restrict patient initially to bedrest for leg elevation and control of edema, if present.
  • Adequate pressure relief from foot wound crucial to healing process.

• Antimicrobial therapy (Tables 1 and 2)
  • Mild, uncomplicated infections treated with oral outpatient antibiotics such as amoxicillin-clavulanate.
    • Does not cover P. aeruginosa
    • Fluoroquinolones with metronidazole or clindamycin reasonable alternatives.
    • Treat 7–14 days.
  • Moderate to severe infections
    • Monotherapy with broad-spectrum parenteral antimicrobials plus appropriate medical and/or surgical management often effective (including those with presence of osteomyelitis).
      • Initial therapy similar to that for polymicrobic cellulitis with anaerobes.
      • Treat 2–4 weeks.
      • Treat 6–12 weeks if osteomyelitis is present.
      • Vancomycin used frequently in severe infections with gram-positive pathogens. With increasing staphylococcal resistance, linezolid, quinupristin/dalfopristin, daptomycin, and tigecycline are alternatives.