Synopsis
Diagnose diabetic foot infection clinically, grade limb and systemic threat, obtain deep microbiology and coordinate debridement, perfusion restoration, offloading and antimicrobial treatment.
- Diabetic foot infection is a clinical diagnosis: purulence or at least two local inflammatory features must be attributed to infection, not culture alone.
- Do not give antibiotics to an uninfected ulcer; colonisation is expected and treatment does not promote healing.
- Remove dressings, inspect between toes and examine depth, undermining, necrosis, fluctuance, deformity, sensation and perfusion.
- Grade infection as mild, moderate or severe because extent, depth and systemic features determine setting, spectrum and urgency.
- After cleaning and debridement, obtain deep tissue or curettage for culture; avoid using a superficial swab when a better sample is feasible.
- Plain radiography is the initial bone study; MRI is the preferred advanced imaging test when osteomyelitis remains uncertain.
- Antibiotics are only one component: drainage, debridement, offloading, perfusion restoration, glucose management and wound care determine outcome.
- For a mild infection, NICE lists flucloxacillin 500 mg to 1 g four times daily for seven days as a first-choice adult regimen, with review and culture adjustment.
Key red flags
Hypotension, confusion, tachypnoea, lactate rise or oliguria indicates severe infection with organ dysfunction.
Crepitus, bullae, anaesthesia, necrosis or disproportionate pain suggests necrotising soft-tissue infection.
Fluctuance, purulent tracking or pain with passive movement suggests a deep abscess or compartment infection.
Cool skin, absent pulses, rest pain, gangrene or delayed capillary return indicates limb-threatening ischaemia.
Visible or probe-detectable bone, chronic deep ulcer or persistent inflammatory drainage raises osteomyelitis probability.
Neuropathy can remove pain, so an apparently comfortable patient may still have extensive infection.
Erythema extending more widely, lymphangitis, abscess, gangrene or involvement of tendon, muscle, joint or bone requires urgent multidisciplinary assessment.
Temperature disturbance, tachycardia, tachypnoea, hypotension, confusion or metabolic deterioration makes infection severe and usually requires admission.
Cool pale or cyanosed skin, absent pulses, dependent rubor, rest pain, tissue loss or gangrene suggests inadequate perfusion and poor healing capacity.
Loss of protective sensation can make deep infection painless; callus, deformity and an unexpectedly deep ulcer are important danger clues.
Investigation priorities
Define ulcer size, depth, undermining, exposed structures, drainage and viable versus necrotic tissue.
Management branches
A person with diabetes has a new ulcer, drainage, redness, swelling or unexplained metabolic deterioration.
- Use ABCDE when systemically unwell, remove all dressings and inspect both feet, interdigital spaces, footwear and the entire affected limb.
- Clean and debride enough to assess ulcer depth, purulence, necrosis, fluctuance, exposed tendon or bone, sensation and deformity.
- Assess pulses, temperature, capillary return and Doppler signals and classify both infection severity and ischaemic urgency.
- Refer immediately through the diabetic-foot multidisciplinary pathway when moderate, severe, deep, ischaemic or rapidly progressive disease is present.