infected leg ulcer

Last edited 07/2021 and last reviewed 07/2021

A leg ulcer is a long-lasting (chronic) open wound that takes more than 4 to 6 weeks to heal.

Leg ulcers usually develop on the lower leg, between the shin and the ankle.


Studies suggest that 80% to 100% of leg ulcers may have bacteria (usually Staphylococcus aureus or Pseudomonas aeruginosa) present in the wound, but this does not necessarily mean the wound is infected (1).

The clinician should be aware that:

  • there are many causes of leg ulcers: underlying conditions, such as venous insufficiency and oedema, should be managed to promote healing most leg ulcers are not clinically infected but are likely to be colonised with bacter
  • antibiotics do not help to promote healing when a leg ulcer is not clinically infected

Do not take a sample for microbiological testing from a leg ulcer at initial presentation, even if it might be infected.

Antibiotics should only be offered for adults with a leg ulcer when there are symptoms or signs of infection:

  • for example, redness or swelling spreading beyond the ulcer, localised warmth, increased pain or fever)
  • when choosing an antibiotic take account of:
    • severity of symptoms or signs
    • risk of developing complications
    • previous antibiotic use
  • oral antibiotics should be given if the person can take oral medicines, and the severity of their condition does not require intravenous antibiotics
  • if intravenous antibiotics are given, review by 48 hours and consider switching to oral antibiotics if possible.

Key points (2):

  • manage any underlying conditions to promote ulcer healing
  • only offer an antibiotic when there are symptoms or signs of infection (such as redness or swelling spreading beyond the ulcer, localised warmth, increased pain or fever). Few leg ulcers are clinically infected but most are colonised by bacteria
  • when prescribing antibiotics, take account of severity, risk of complications and previous antibiotic use.

Reference: