diabetic foot infection

Classification

• mild infections
  • do not extend deeper than skin & subcutaneous tissue
  • may be associated with purulence, warmth, tenderness, edema
  • erythema extends < 2 cm beyond ulcer
• moderate infection
  • erythema extends > 2 cm beyond ulcer
  • infection extends deeper than skin & subcutaneous tissue
• severe infection
  • associated with systemic signs of infection
    • hypotension, confusion, metabolic acidosis, acute kidney injury, severe hyperglycemia

Diagnostic criteria

• pus, purulent drainage, foul odor or >= 2 signs of inflammation

Laboratory

• deep tisue culture (curettage or tissue biopsy) prior to antibiotic therapy
• bone culture if bone biopsy

Diagnostic procedures

• assess for arterial insufficiency using ankle-brachial index
• positive probe to bone test suggests osteomyelitis
• bone biopsy if suspected osteomyelitis

Radiology

• foot X-ray (all patients)*
• ultrasound if abscess
• MRI if osteomyelitis suspected (but not confirmed on X-ray or probe to bone test)#

* if sepsis, empiric antibiotics prior to foot X-ray *

imaging modalities

Modality	sensitivity	specificity
plain radiography	0.54	0.68
leukocyte scan	0.74	0.68
3-phase bone scan	0.81	0.28
MRI	0.90	0.79

Management

• wound care (see diabetic foot ulcer)
  • assess need for surgical debridement, revascularization, amputation
• glycemic control
• off-loading of biomechanical stress
• antibiotic therapy:
  • diabetic foot infections diagnosed clinically (see Diagnostic criteria:)
    • avoid antibiotics in the absence of signs or symptoms of infection
  • empiric antibiotics should cover gram positive bacteria including S aureus
    • empiric coverage should include Pseudomonas for Asians & North Africans
  • mild non-purulent infections (see classification)
    • oral cephalexin, dicloxacillin, amoxicillin clavulanate or clindamycin
  • mild purulent infection
    • oral doxycycline or trimethoprim-sulfamethoxazole with a beta-lactam
  • moderate infections (see classification)
    • outpatient treatment for MRSA only if risk factors (see MRSA)
      • amoxicillin clavulanate + ciprofloxaxin for 14 days if no risk factors for MRSA provides dual coverage for Pseudomonas aeruginosa
  • severe infections
    • IV beta piperacillin tazobactam, carbapenem or metronidazole + fluroquinolone or 3rd generation cephalosporin + vancomycin, daptomycin or linezolid (MRSA)
    • vancomycin, cefepime & metronidazole for sepsis
  • antibiotic duration for skin & soft tissue infection
    • 1-2 weeks, up to 4 weeks may be necessary if improvement is slow
• diabetic foot osteomyelitis
  • therapy guided by results of bone culture from bone biopsy
  • adjunctive rifampin associated with improved amputation-free survival
  • 6 weeks of antibiotics for osteomyelitis without amputation
    • 3 weeks after amputation with positive bone margins
  • 3 weeks of antibiotics may be non-inferior to 6 weeks
• G-CSF, topical antiseptics, silver, honey, bacteriophages, topical antibiotics, & hyperbaric oxygen not recommended

Notes

• also see diabetic foot ulcer

More general terms

• foot infection

Additional terms

• diabetic foot
• diabetic foot ulcer; diabetic foot lesion; diabetic lower extremity lesion