What is the treatment for common foot infections?

Treatment of Common Foot Infections

The treatment of common foot infections requires appropriate antibiotic therapy based on infection severity, combined with proper wound care and, when necessary, surgical intervention to prevent limb-threatening complications and reduce mortality.

Classification and Assessment

• Foot infections should be categorized by severity (mild, moderate, or severe) based on clinical features including tissue involvement, arterial perfusion, and presence of systemic toxicity 1.
• Signs of potentially limb-threatening infections include systemic inflammatory response, rapid progression, extensive necrosis/gangrene, crepitus, bullae (especially hemorrhagic), new onset wound anesthesia, and pain out of proportion to clinical findings 1.
• Diagnosis of infection is primarily clinical, based on local signs of inflammation, rather than laboratory findings 1, 2.

Antimicrobial Therapy

Selection Based on Severity

• Mild infections: Therapy aimed at aerobic gram-positive cocci (especially Staphylococcus aureus and beta-hemolytic streptococci) is usually sufficient for previously untreated infections 1, 3.

  • Oral antibiotics with good bioavailability (dicloxacillin, cephalexin, clindamycin) are appropriate 1, 3.
  • Duration: 1-2 weeks, sometimes requiring an additional 1-2 weeks 1.

• Moderate infections: May require broader coverage depending on chronicity and previous antibiotic exposure 1.

  • Can often be treated with oral antibiotics, but some may require initial parenteral therapy 1.
  • Duration: 2-4 weeks, depending on structures involved, adequacy of debridement, and wound vascularity 1.

• Severe infections: Require prompt initiation of broad-spectrum parenteral antibiotics active against gram-positive cocci, gram-negative rods, and anaerobes 1.

  • Options include ciprofloxacin plus clindamycin, piperacillin/tazobactam, or imipenem/cilastatin 3.
  • Consider local prevalence of MRSA when selecting empiric therapy 1, 3.
  • Duration: 2-4 weeks for soft tissue infections; 4-6+ weeks for osteomyelitis 1.

Important Considerations

• Obtain appropriate cultures before starting antibiotics in all cases except perhaps mild, previously untreated infections 1, 2.
• Tissue specimens from biopsy, ulcer curettage, or aspiration are preferred over wound swabs 1, 2.
• Definitive therapy should be guided by culture results and clinical response to empiric treatment 1.
• For clinically stable patients with non-responding infections, consider discontinuing all antibiotics for a few days before obtaining new cultures 1.

Surgical Management

• Surgical consultation is necessary for all severe infections and selected moderate infections 1, 2.

• Urgent surgical intervention is required for deep abscesses, compartment syndrome, and necrotizing soft tissue infections 1, 2.

• Surgery is typically indicated for infections with 1:

  • Deep abscess formation
  • Extensive bone or joint involvement
  • Crepitus or substantial necrosis/gangrene
  • Necrotizing fasciitis
  • Progressive bone destruction or bone protruding through ulcer

• The surgical approach should be guided by knowledge of foot compartments and how infection spreads through fascial planes 1.

• Infections from the great toe/first metatarsal typically spread through the medial compartment; those from the fifth toe/metatarsal through the lateral compartment; and those from the middle toes/metatarsals through the central compartment 1.

Wound Care

• Proper wound care is crucial for healing and includes 1:

  • Wound cleansing
  • Debridement of callus and necrotic tissue
  • Off-loading of pressure
  • Appropriate dressings

• For dry gangrene, especially on the heel, it may be preferable to leave adherent eschar in place until it softens enough to be removed, provided there is no underlying infection 1.

Special Considerations

Fungal Infections

• For tinea pedis (athlete's foot), topical antifungal agents like terbinafine are effective 4, 5.
  • Application twice daily for 1 week between toes or 2 weeks on bottom/sides of foot 4.
  • Oral therapy should be considered for extensive, resistant, or chronic infections, especially in diabetic patients 5.

Vascular Assessment

• Evaluate arterial supply in infected limbs, especially with signs of ischemia 1.
• Revascularization may be necessary for patients with critical limb ischemia 1.

Osteomyelitis

• Suspected when bone is exposed, probe-to-bone test is positive, or with persistent infection despite appropriate therapy 1, 2.
• Requires extended antibiotic therapy (4-6+ weeks) unless all infected bone is surgically removed 1.
• Imaging studies (plain radiography initially, MRI for more detailed assessment) are helpful for diagnosis 2.

Follow-up and Monitoring

• Early and careful follow-up is essential to ensure that treatment is appropriate and effective 1.
• Monitor for clinical improvement, including reduction in erythema, swelling, pain, and wound size 1.
• Adjust therapy based on clinical response and culture results 1.