A number of bacteria may potentially cause wound infection. These include:

Staphylococcus Aureus

  • Gram-positive sphere shaped
  • Clusters like a bunch of grapes
  • Found in about 30% of population with minimal symptoms
  • Various strains which produce toxins can cause poisoning or toxic shock
  • Delays wound healing
  • Usually treated with penicillin or a cephalosporin which destroy bacteria by interfering with the synthesis of the bacteria cell wall


  • Gram-positive oval in shape
  • Unites like a string of beads
  • Certain strains destroy red blood cells and are called haemolytic Streptococcus
  • Wounds infected with Streptococcus are often very red, painful and tend to bleed easily

Pseudomonas Aeruginosa

  • Gram-negative rod shaped
  • Notoriously resistant to antibiotic therapy
  • Delays healing and increases pain in wound
  • Copious exudate is a distinctive green and also has peculiar, sweet musty smelling odour
  • Responds well to short treatment with silver sulphadiazine

MRSA (Methicillin-resistant Staphylococcus Aureus)

  • First reported in 1980’s
  • Now many different strains
  • Ranges from simple wound colonisation to systemic infection which may be fatal
  • If a wound is infected, it is difficult to manage with antibiotics
  • Local protocol for treating infected wounds should be followed

Necrotising Fasciitis (Less Common)

A serious bacterial infection caused by Streptococcus pyogenes or Staphylococcus aureus. Typical signs in wounds are redness, heat, swelling, pain, and rapidly spreading inflammation with dusky purple patches over the inflamed sites. The dark patches rapidly spread to gangrene. Early diagnosis and treatment is vital.