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Infection or Inflammation

Clinical studies have shown that wounds that do not heal often have a high bacterial burden. This implies a connection between high bacterial burden in the wound bed and the failure of chronic wounds to heal. Decreasing this bacterial burden is a vital element of Wound Bed Preparation.


Infection and bacterial burden

Chronic wounds are known to exist along a bacterial continuum, which ranges from contamination to infection. To heal a wound it is important to determine where the wound is positioned on this continuum, by recognising the signs and symptoms of local infection, and then deciding how the wound can be managed effectively.


The presence of bacteria within a wound can be divided into four distinct categories:
Contamination - The presence of non-replicating micro organisms within the wound.
Colonisation - The presence of replicating micro organisms that do not cause injury to the host.
Critical colonisation - The presence of replicating micro organisms that are beginning to cause local tissue damage. Critical colonisation describes wounds that have an increased bacterial burden that is transitioning between colonisation and local infection. During critical colonisation, subtle clinical signs of infection may be present.


These clinical signs and symptoms of local infection are:
Delayed healing
Change in colour of the wound bed
Friable granulation tissue
Absent or abnormal granulation tissue
Abnormal odour
Increased serous exudate
Increased pain at the wound site


Infection - The presence of replicating micro organisms that are capable of causing injury to the host.


This is regarded as systemic infection, and the classic signs and symptoms are:
Advancing redness (erythema)
Warmth at the wound site
Oedema (swelling)
Foul odour


Variables that affect wound infection
A number of variables are known to affect the bacterial burden of a wound and increase the risk of infection, including the number of micro organisms present in the wound, bacterial virulence and host resistance factors. The way in which these factors are related can be demonstrated in the following equation:


Risk of wound infection = bacterial dose x virulence host resistance

Antimicrobials can be used to reduce colonisation and infection in wounds. Without the appropriate use of antimicrobials during wound bed preparation, bacteria will continue to thrive, thereby delaying wound closure. Antibiotics are also commonly used as antimicrobial agents but, due to the growing concerns about developing resistance to antibiotics, their use has been reduced, in many situations.