Diabetic foot infections

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Foot infections in persons with diabetes are a common, complex, and costly problem.
In addition to causing severe morbidities, they now account for the largest number of diabetes related hospital bed days and are the most common proximate, nontraumatic cause of amputations.
Diabetic foot infections require careful attention and coordinated management, preferably by a multidisciplinary foot-care team.

Illness, drug, dose,frequency and duration information

Management
  • Only use antibiotics if clinical signs of infection
  • Send microbiological samples early in infection – tissue aspirates are preferable to wound swabs
  • Continue therapy until the infection has resolved, not until the wound has healed
  • Treatment plan should include wound care, pressure relief and early vascular assessment, with referral to vascular surgeons if impalpable foot pulses.
  • Foot ischaemia may increase the severity of any infection, and the presence of critical ischaemia often makes the infection severe
  • Typical pathogens (antibiotic-naïve = no systemic antimicrobials in last 3 months)
    • antibiotic-naïve: Staph aureus and beta-haemolytic streptococci
    • not antibiotic-naïve or chronic: as above plus Gram-negative bacilli, enterococci, anaerobes
  • Osteomyelitis
    • suspect if able to touch bone through the wound with a sterile probe
    • suspect in a non-healing diabetic ulcer with adequate blood supply
    • refer to Combined Diabetic Foot Clinic
    • deep swab or tissue samples are essential for diagnosis. Delay therapy pending microbiology results in chronic cases
    • treat for 6 weeks minimum
  • Classify using IDSA grading of severity of diabetic foot infection in Table below- see Lipsky, B. A. et al., 2004. Diagnosis and Treatment of Diabetic Foot Infections. Clinical Infectious Diseases, 39, pp. 885-910
Clinical classification of a diabetic foot infection (from reference above)
Clinical manifestations of infection

Infection severity

PEDIS grade

Wound lacking purulence or any manifestations of inflammation
Uninfected
1
Presence of ≥ 2 manifestations of inflammation (purulence, or erythema, pain, tenderness, warmth, or induration), but any cellulitis/erythema extends ≤2 cm around the ulcer, and infection is limited to the skin or superficial subcutaneous tissues; no other local complications or systemic illness.
Mild
2
Infection (as above) in a patient who is systemically well and metabolically stable but which has 1 of the following characteristics: cellulitis extending 12cm, lymphangitic streaking, spread beneath the superficial fascia, deep-tissue abscess, gangrene, and involvement of muscle, tendon, joint or bone.
Moderate
3
Infection in a patient with systemic toxicity or metabolic instability (eg, fever, chills, tachycardia, hypotension, confusion, vomiting, leukocytosis, acidosis, severe hyperglycaemia, or azotaemia).
Severe
4
PEDIS: Perfusion, Extent/size, Depth/tissue loss, Infection, and Sensation.

Refer to Highland formulary for up to date recommendations on antibiotic therapy based on severity of infection, presence of osteomyelitis and whether antibiotic naïve.

See also Diabetic foot problem admission and referral guideline (link to be added)

Editorial Information

Last reviewed: 12 May 2020

Next review: 31 May 2023

Author(s): Foot MDT

Version: 1

Approved By: TAM Subgroup of ADTC

Reviewer Name(s): Consultant Physician

Document Id: TAM151