diabetic%20foot%20infection
DIABETIC FOOT INFECTION

Diabetic foot infection occurs in patients with diabetes as they are prone to microorganism invasion and multiplication in the soft tissue or bone (anywhere below the malleoli) that leads to host inflammatory response that usually results to tissue destruction.

Staphylococci and streptococci are the most common causative organisms although most diabetic foot infections are polymicrobial.

Most infections usually start with a break in the protective cutaneous envelope of the skin that resulted from trauma or neuropathic ulceration.

Management of diabetic foot ulcer in patients with diabetes needs an interdisciplinary approach to address glycemic control, infection, offloading of high-pressure areas, lower extremity vascular status and local wound care.

Principles of Therapy

  • Management of diabetic foot ulcer in patients w/ diabetes needs an interdisciplinary approach to address glycemic control, infection, offloading of high-pressure areas, lower extremity vascular status & local wound care
  • Mild diabetic foot infections are treated in outpatient setting w/ oral antibiotics, wound care & pressure offloading
  • Selected patients w/ moderate diabetic foot infections & all patients w/ severe infections will be given intravenous antibiotics & to be evaluated for possible surgical intervention while staying in the hospital
  • For diabetic foot wounds that have no evidence of soft tissue or bone infection, antibiotic therapy is not required
  • For infected wounds, obtain a post-debridement specimen (preferably of tissue) for aerobic & anaerobic cultures

Pharmacotherapy

  • Selection of specific antibiotic therapy should be based on:
    • Causative pathogens that are likely or proven
    • Susceptibility to the antibiotic
    • Clinical severity of the infection
    • Evidence of efficacy for diabetic foot infection
    • Costs
  • Infected diabetic foot wound that has failed antimicrobial therapy is usually associated w/ progressive tissue destruction & poor wound healing
  • The most common pathogens when infection first begins are Staphylococcus aureus, Streptococcus agalactiae, & Streptococcus pyogenes
    • Anaerobic & Gram-negative pathogens can play a role in the process w/ time & the presence of devitalized tissue that leads to polymicrobial infections
  • Parenteral therapy is initially administered in some moderate infections & most severe infections then switch to oral therapy when the infection is responding
  • Empiric antibiotic regimen should cover the most common infecting organisms, usually active against standard strains of staphylococci & streptococci, & then be modified according to infection severity & available clinical or microbiological information
  • For mild infections, oral narrow-spectrum antibiotics w/ activity against aerobic gram-positive organisms are preferred to be given for 1-2 weeks
    • It is not advisable to give prolonged antibiotic treatment (eg >14 days) in mild soft tissue diabetic foot infection
  • Anti-anaerobic empiric therapy is given for necrotic, gangrenous or foul-smelling wounds that also require debridement
  • Combination therapy is given when:
    • The presumed or proven cause of the infection is >1 microorganism
    • The pathogen has a high potential for developing resistance
    • Selecting an agent to which resistance may quickly develop when used alone
  • Once the results of the culture & sensitivity tests are available, consider changing to a more specific regimen that targets just the isolated pathogens
  • Generally, antibiotic therapy can be discontinued when signs & symptoms of infection have resolved, even if the wound has not healed
Suggested Empiric Antibiotic Therapy
Infection Severity Recommended Antibiotics
Mild (Gram-positive cocci w/ or without methicillin-resistant Staphylococcus aureus) Co-amoxiclav, Cefdinir, Cephalexin, Clindamycin, Dicloxacillin, Doxycycline, Levofloxacin, Linezolid, Minocycline, Co-trimoxazole
Moderate to Severe (Gram-positive cocci; gram-negative rods; anaerobes w/ or without multidrug-resistant organisms)
Sultamicillin, Cefoxitin, Ceftriaxone, Clindamycin/fluoroquinolones, Daptomycin, Ertapenem, Imipenem/Cilastatin, Linezolid, Levofloxacin, Moxifloxacin, Piperacillin/Tazobactam, Ticarcillin/clavulanate, Tigecycline, Vancomycin
Modify treatment regimen for optimal therapy once culture & susceptibility results are available

Diabetic Foot Osteomyelitis

  • When treating diabetic foot osteomyelitis, the following should be considered:
    • Anatomic site of infection
    • Local vascular supply
    • Soft tissue & bone destruction extent
    • Presence of any systemic signs of infection
    • Patient’s preference for treatment
  • Antimicrobial agent should be based on the results of a bone culture, especially because of the need for long-duration therapy
  • When empiric therapy is needed, therapy usually covers S. aureus as it is the most common pathogen, but the patient’s history or culture results may suggest a need for broader coverage
  • Antibiotic therapy of 6 weeks duration is recommended in patients w/ diabetic foot osteomyelitis that did not undergo resection of the infected foot while 1-week duration for those who have all infected bone resected
  • Remission rate does not appear to increase when post-debridement antibiotic therapy is extended beyond 6 weeks or if IV treatment is given longer than a week
  • Long-term suppressive therapy or intermittent short courses of treatment of recrudescent symptoms can be the appropriate approach for patients who have apparently incurable infection
  • Patients with diabetic foot ulcers may also be given recombinant human epidermal growth factor as data have shown that it enhances wound healing and shortens healing time

Non-Pharmacological Therapy

Wound Care

  • Essentials of wound care in a diabetic patient w/ foot wound include:
    • Debridement
    • Offloading
    • Selection of dressings
  • Debridement is the removal of debris, eschar, surrounding callus or devitalized tissue that may impede wound healing & foster infection
    • It is essential in nonischemic wound to have regular debridement of nonviable tissue
    • Generally, sharp/surgical method of debridement is used but mechanical, autolytic or larval debridement techniques may be appropriate for some wounds
  • Offloading is the redistribution of pressure off the wound to the entire weightbearing surface of the foot
    • This may be achieved by using temporary footwear until the ulcer heals & foot character stabilizes
    • Pressure-reducing devices (eg removable & irremovable cast walkers & total contact casting) have demonstrated efficacy in plantar surface ulcers
    • Pressure-relief devices that cannot be removed are associated w/ faster healing ulcers than are removable devices as per clinical trials
    • Consultation w/ surgeon skilled in foot surgery is suggested to address bony deformities that prevent the fitting of appropriate footwear &/or offloading of pressure-related ulcers
  • Appropriate selection of dressings that allow for moist wound environment & control of excess exudation is necessary in wound care
    • In general, dry wound needs topical treatment that adds moisture while diabetic foot ulcers w/ heavy exudate need a dressing that absorbs moisture
    • Dressings should be changed at least daily, both to apply a clean wound covering & to allow careful examination of the wound for infection
    • Povidone iodine impregnated wound dressings may be considered for infected diabetic foot ulcers
  • There is mixed evidence supporting the use of hyperbaric oxygen therapy as an adjunctive treatment to standard diabetic foot wound care 
Editor's Recommendations
Most Read Articles
Pank Jit Sin, 03 Dec 2018
Prominent members from the Malaysian Society of Allergy and Immunology (MSAI) and Dermatological Society of Malaysia (PDM) came together to establish a coalition called the Malaysian Urticaria Expert Group (MARTEG).