Diabetic foot infection (DFI)

[Clin Infect Dis 2023; ciad527, https://doi.org/10.1093/cid/ciad527]

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General Management

- Prevention is key - proper foot care & glycemic control are essential.

- Vascular assessment essential.

- Pressure relief on ulcers (off-loading) very important, e.g. non-weight bearing on affected foot, contact casting.

- Debridement of devitalized tissue is essential.

- Recommend timely referral to multidisciplinary diabetic foot team, where available.

Diagnosis

- Not all diabetic foot wounds are infected.  No evidence to support using systemic or local antibiotic therapy to decrease bioburden of wounds in order to enhance healing or to prevent infection of wound.

 - Diagnosis of infection based on:

1. Presence of purulent secretions, OR at least two signs or symptoms of inflammation:

• erythema

• warmth

• pain

• tenderness

• induration and/or swelling
  or

• systemic signs and symptoms of infection (fever, increased WBC).

2. Wound cultures - post debridement deep tissue specimens (biopsy or curettage) or aspiration of purulent secretions recommended as correlation of superficial wound swabs/cultures to pathogens poor. Repeat cultures are not recommended unless obvious clinical deterioration.

3. Imaging:

- All patients with DFI should have plain x-ray. NB: X-ray abnormalities lag clinical infection by up to one month. Repeat x-rays indicated if deep and/or unresolving ulcer.

- Further imaging recommended if:

• deep space infection/bone fragments in ulcer/nonhealing wound

• sinus tract

• putrid smell

• ESR >70.

- MRI best study to diagnose and assess extent of soft tissue and bone and joint involvement. WBC scan +/- bone scan best alternative if MRI not available.

• Mild - skin and subcutaneous tissues involved

• Moderate-severe - deeper infection, systemic signs of infection or metabolic instability

- Osteomyelitis is more likely if ulcer > 2 cm², exposed bone or ulcer overlies bony prominence, positive probe to bone, ESR > 70 or abnormal plain x-ray.

Antibiotic Therapy

- Pseudomonas coverage not always necessary as P. aeruginosa is often a non pathogenic colonizer of diabetic wounds. Empiric coverage of P. aeruginosa should be considered if:

• tropical/warm climates

• soaking of feet

• failed nonpseudomonal therapy

• limb-threatening infection.

- MRSA coverage recommended if:

• previous (prior 12 months)/current colonization/infection with MRSA

• recent antibiotic use

• recent hospitalization.