Wound infection

Author: Vanessa Ngan, Staff Writer, 2005.

What is a wound infection?

A wound infection is defined by the US Centre for Disease Control and Prevention (CDC) as surgical site infection (SSI). This is further defined as:

Although this definition of wound infection is restricted to those arising from a surgical incision, a broader and more general definition would be infection of a wound caused by physical injury of the skin as a result of penetrating trauma from plants, animals, guns, knives or other objects. Wounds break the continuity of the skin and allow organisms to gain access to tissues and cause infection.

Infections arising in surgical wounds are one of the most common hospital acquired infections and are an important cause of morbidity and mortality. Hence, the focus of this article is on the recognition and management of surgical wound infections.

What defines a surgical wound infection?

A surgical wound/site infection is defined by the following criteria:

  1. Infection must occur within 30 days of the surgical operation; and;
  2. At least one of the following:

Other signs of wound infection include:

Surgical site infections do not include a stitch abscess, episiotomy infection, newborn circumcision scar, or infected thermal burn wound.

What causes a wound infection?

Wound infections are caused by the deposition and multiplication of microorganisms in the surgical site of a susceptible host. There are a number of ways microorganisms can get into wounds.

The most common causative organisms associated with wound infections include Staphylococcus aureus/MRSA, Streptococcus pyogenes, Enterococci and Pseudomonas aeruginosa.

Contributing factors

General patient characteristics

Wound characteristics

Operative characteristics

What is the risk of wound infection?

The risk of wound infection varies with the type of surgery. Certain types of surgery carry a higher risk of contamination than others and have led to the following classification of surgical wounds.

Clean wound, for example hernia repair

Clean-contaminated wound, for example appendectomy

Contaminated wound, for example colectomy due to obstruction

Dirty wound

What is the management of wound infections?

The goal of wound infection management is to prevent or minimise the risk of infection. The following factors or methods external to the patient are used to prevent infection.

Theatre environment and care of instruments

Surgical team members educated in aseptic technique

Techniques applied to the patient to prevent wound infections include:

Antiseptic cleansers are adequate for clean wounds or lightly contaminated wounds. Antibiotic prophylaxis may be indicated for clean-contaminated wounds and is usually recommended for contaminated wounds. Antibiotics for dirty wounds are part of the treatment because infection is already established. When deciding on a prophylactic antibiotic consider the following:

Wound infection can complicate illness, cause anxiety, increase patient discomfort and lead to death. It is estimated that surgical wound infections result in an increased length of hospital stay by about 7–10 days. Hence the prevention and management of wound infection has a major impact on both patient health and health economics.

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