Diabetic Foot Infection

VASP

Foundational Principles 

  • Do NOT use antibiotics to treat uninfected wounds as patient harm outweighs benefit.
  • ALL wounds are colonized with microorganisms and superficial wound cultures should not be collected nor used to make treatment decisions.
  • Do NOT administer antibiotics to clinically stable patients until deep tissue or operative cultures are obtained.
  • Failure of oral antibiotics used for < 48 hours is NOT a reason to use broad-spectrum antibiotics.

Evaluation 

  • Plain radiograph for all pts; MRI w/contrast if abscess/osteo suspected
  • Use of inflammatory markers such as ESR or CRP at baseline may help determine level of inflammation with periodic trending (e.g. weekly) thereafter. Do NOT repeat these tests daily.
  • BCx (prior to antibiotics) if systemic signs of infection, or severe infection
    • Do not culture superficial swabs of lesions, as these generally only grow colonizing organisms.
  • Consider obtaining MRSA nasal PCR. (ensure collected before nasal decolonization); ~90% negative predictive values for diabetic foot infections
  • Consult podiatry if osteomyelitis present for bone specimen culture and pathology (either from debridement specimen or bone biopsy) prior to starting antibiotics.
  • Consult surgery if concern for abscess, gas in tissue, joint involvement
  • Assess peripheral vasculature, consider arterial flow studies/vascular surgery consult

Management 

  • Assess Severity:
    • Mild: local infection, skin/subcutaneous tissue only, erythema >0.5 cm but ≤2cm from ulcer
    • Moderate: local infection w/erythema > 2 cm from ulcer or deeper structures included without SIRS
    • Severe: local infection with systemic inflammation as evidenced by >2 SIRS criteria
  • Consider anti-pseudomonal coverage only if at risk for Pseudomonas infection (e.g. previous Pseudomonas on culture, water exposure; hospitalization within previous 90 days AND IV antibiotic use, immunocompromise).
  • Consider MRSA coverage with risk factors: previous MRSA on cultures, hospitalization within previous 90 days AND IV antibiotic use, IV drug use, hemodialysis
  • Consider anaerobic coverage with metronidazole

Non-purulent, no MRSA risk factors

Purulent, MRSA risk factors
Mild Preferred:
  • Cephalexin 500mg PO QID or 1g TID
  • Cefadroxil 1g PO BID (upon discharge only)
Alternative:
  • Amoxicillin/clavulanate 875/125mg PO BID
MRSA only with risk factors:
  • Doxycycline 100mg PO BID (add to ß-lactam)
Trimethoprim/sulfamethoxazole 5- 8mg/kg/day (alone)—Preferred if severe penicillin allergy 		7-14 days
Moderate Preferred:
  • Ampicillin/sulbactam 3g IV Q6H
  • Ceftriaxone 2g IV daily ± PO metronidazole 500mg Q12H
P. aeruginosa only with risk factors (change to):
  • Piperacillin/tazobactam 3.375g IV Q8H ext infusion
  • Cefepime 2g IV Q8H ± metronidazole 500mg PO Q12H
  • Levofloxacin 750mg PO daily ± metronidazole 500mg PO Q12H
MRSA only with risk factors (add):
  • Doxycycline 100mg PO BID
  • Trimethoprim/sulfamethoxazole 5-8mg/kg/day for SSTI and 8- 12mg/kg/day for osteomyelitis
  • Linezolid 600mg PO BID Vancomycin (pharmacy consult)
 7 – 21 days for soft tissue infection only
If osteomyelitis:
  • 24-48 hours if complete resection of infected tissue
  • 1 – 3 weeks if only residual soft tissue infection
  • 3 – 6 weeks if residual bone infection with resection or 4 – 6 weeks without resection
Severe Preferred:
  • Ceftriaxone 2g IV daily + metronidazole 500mg PO Q12H PLUS
  • Vancomycin (pharmacy consult)
  • Linezolid 600mg PO BID⁺
P. aeruginosa only with risk factors (change to):
  • Piperacillin/tazobactam 3.375g IV Q8H ext infusion
  • Cefepime 2g IV Q8H + metronidazole 500mg PO Q12H
⁺Linezolid is preferred for use in necrotizing soft tissue infections
Adjust regimen based on deep culture results 		7 – 28 days for soft tissue infection only
If osteomyelitis:
  • 48 hours if complete resection of infected tissue
  • 7 - 21 days if only residual soft tissue infection
  • 21 - 42 days if residual bone infection with resection or 28 - 42 days without resection

Conversion to PO antibiotics (including osteomyelitis): 

  • Active agent available
  • Functioning GI tract
  • Clinically stable
  • Select active agent(s) against recovered pathogen(s)

Additional Information 

  • If pt HDS, hold abx until deep tissue/operative cultures obtained.
  • Most diabetic foot infections are polymicrobial in nature.
  • Culture results will help therapy, but all pathogens identified may not require treatment. Would discuss with ID if complex
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