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 beta-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) OR -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