Clinical Setting
General management:
Glucose control; eliminate pressure on ulcer, if present.Assess for peripheral vascular disease.
Principles guiding empiric therapy:Include a drug predictably active vs MRSA.Empiric drug regimens should cover both staph and strep; role of enterococci is uncertain.Severe limb and/or life-threatening infections require initial parenteral therapy with predictable activity against Gram-positive cocci, coliforms and other aerobic Gram-negative rods and anaerobic Gram-negative bacilli.
Risk of osteomyelitis increased if ulcer area >2 cm2, positive probe to bone, ESR >70 and abnormal plain x-ray.
MRI is best imaging modality: negative MRI reduces likelihood of osteomyelitis (JAMA 299:806, 2008).
Review of diagnostic accuracy of probe to bone (Clin Infect Dis 2016;63:944 and Clin Infect Dis 2016;63:949).
Etiologies:
Ulcer, but no inflammation: colonizing skin flora
Ulcer with superficial inflammation:
Staphylococcus aureus (assume methicillin-resistant (MRSA) until proven otherwise)
Streptococcus agalactiae (Group B)
Streptococcus pyogenes
Ulcer with inflammation, extension into fascia As above + coliforms.
Extensive local inflammation and deep tissue invasion plus systemic toxicity As above + anaerobes.
Primary Regimens:
Ulcer, but no inflammation: No antimicrobial therapy recommended.
Moderate strength evidence for improved healing with biologic skin equivalent or negative pressure wound therapy: Ann Intern Med 159:532, 2013.
Ulcer with superficial inflammation:Oral therapy, to cover MRSA: TMP-SMX-DS 1-2 tabs po bid or Doxycycline 100 mg po bid
or Clindamycin
300-450 mg po tid
Oral therapy, mild infection, no MRSA present: Cephalexin 500 mg qid or Cefpodoxime
200 mg po q12h
or Levofloxacin 750 mg po q24h or Amoxicillin-clavulanate extended release 2000/125 po bid.
Ulcer with inflammation, extension into deeper tissues:Oral therapy:(Amoxicillin-clavulanate extended release 2000/125 po bid + TMP-SMX-DS 1-2 tabs po bid) or [(Ciprofloxacin 750 mg po bid or Levofloxacin 750 mg po q24h or Moxifloxacin 400 mg po q24h) + (Linezolid 600 mg po bid)] OR
Parenteral therapy [based on prevailing susceptibilities]:(Ampicillin-sulbactam 3 gm IV q6h or Ertapenem 1 gm IV q24h) + Vancomycin 15-20 mg/kg IV q8-12h (until MRSA is excluded).Extensive local inflammation plus systemic toxicity:
Parenteral therapy [based on prevailing susceptibilities]:
Vancomycin 15-20 mg/kg IV q8-12h + Piperacillin-tazobactam 3.375 gm IV q6h (or 4.5 gm IV q8h or 4-hour infusion of 3.375 gm q8h) OR
Vancomycin 15-20 mg/kg IV q8-12h + (Imipenem-cilastatin 0.5 gm IV q6h or Meropenem 1 gm IV q8h).
Alternative Regimens:
Extensive local inflammation plus systemic toxicity:Daptomycin 6 mg/kg IV q24h or Linezolid 600 mg po bid are alternatives for Vancomycin.
[(Ciprofloxacin 400 mg IV q12h or Levofloxacin 750 mg IV q24h or Aztreonam 2 gm IV q8h) + Metronidazole 0.5 gm IV q6-8h are alternatives for Ampicillin-sulbactam or Piperacillin-tazobactam.
Amoxicillin-clavulanate 1000/200 mg IV q8h (where available).
Antimicrobial Stewardship
Improved outcomes of more effective and faster wound healing of diabetic foot ulcer with negative-pressure wound therapy.Obtain cultures of inflamed ulcer or wound to permit targeted antimicrobial therapy: de-escalate/modify regimen based on culture and susceptibility data.Oral therapy with a bioavailable antibiotic as effective as parenteral therapy.
Comments:
For review see Curr Opin Infect Dis 2016; 29:145-52.See IDSA practice guidelines for additional treatment options: Clin Infect Dis 54:e132, 2012.For primary and secondary preventive measures see: N Engl J Med 2017; 376: 2367.
TMP-SMX may cause hyperkalemia in diabetics.
Use the higher dose of Clindamycin or TMP-SMX in those with BMI > 40.
Cochrane review of safety and efficacy of antimicrobials used to treat diabetic foot infection with or without osteomyelitis: Cochrane Database Syst Rev. 2015 Sep 4;(9):CD009061). SANFORD GUIDE 2018
Diabetic Foot
