A wound infection occurs when germs, such as bacteria, grow within the damaged skin of a wound. Symptoms can include increasing pain, swelling, and redness. More severe infections may cause nausea, chills, or fever.
A person may be able to treat minor wound infections at home. However, people with more severe or persistent wound infections should seek medical attention.
An infected wound is a localized defect or excavation of the skin or underlying soft tissue in which pathogenic organisms have invaded into viable tissue surrounding the wound. Infection of the wound triggers the body’s immune response, causing inflammation and tissue damage, as well as slowing the healing process. Many infections will be self-contained and resolve on their own, such as a scratch or infected hair follicle. Other infections, if left untreated, can become more severe and require medical intervention.
The skin is the body’s first line of defense, the surface of which is protected by a thin, acid film produced by the sebaceous glands called the acid mantle. This acid mantle is a dynamic barrier that regulates the skin’s pH and maintains microorganisms called the normal flora that help prevent pathogens from entering the body. Pathogens will often displace some of the normal flora and colonize certain locations, but most of the time this does not lead to infection and does not stimulate an immune response. However, when the skin is broken or if the immune system becomes compromised, any of the microorganisms colonizing the skin or introduced to the wound can cause an infection. The microorganisms likely to infect a wound depend predominantly on what microorganisms are present on the skin, as well as the depth and location of the wound.

Etiology
Most infected wounds are caused by bacterial colonization, originating either from the normal flora on the skin, or bacteria from other parts of the body or the outside environment. The most common infection-causing bacteria is Staphylococcus aureus and other types of staphylococci.
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.
- Direct contact – transfer from surgical equipment or the hands of the surgeons or nurses
- Airborne dispersal – surrounding air contaminated with micro-organisms that deposit onto the wound
- Self-contamination – physical migration of the patient’s own endogenous flora which is present on the skin, mucous membranes or gastrointestinal tract to the surgical site.
What defines a surgical wound infection?
A surgical wound/site infection is defined by the following criteria. Infection must occur within 30 days of the surgical operation, and at least one of the following must occur:
- Purulent discharge from the surgical site
- Purulent discharge from wound or drain placed in the wound
- Organisms isolated from the aseptically obtained wound culture
- Must be at least one of the signs and symptoms of infection – pain or tenderness, localised swelling, or redness/heat.
Other signs of wound infection include:
- Delayed healing not previously anticipated.
- Discolouration of tissues both within and at the wound margins.
- Abnormal smell coming from the wound site.
- Friable, bleeding granulation tissue despite appropriate care and management.
- Lymphangitis, a red line originating from the wound and leading to swollen tender lymph glands draining the affected area.
Surgical site infections do not include a stitch abscess, episiotomy infection, newborn circumcision scar, or infected thermal burn wound.
Symptoms of Infected Wounds
People can usually safely treat small wounds, such as minor cuts and scratches, at home. With proper care, most small wounds will gradually get better until they fully heal.
If a wound becomes infected, however, it can get worse instead of better. Any pain, redness, and swelling will typically increase in intensity.
Wound infections can also lead to other symptoms, such as:
- warm skin around the wound
- yellow or green discharge coming from the wound
- the wound giving off an unpleasant odor
- red streaks on the skin around the wound
- fever and chills
- aches and pains
- nausea
- vomiting
Risk factors
Cuts, grazes, and other breaks in the skin can become infected when bacteria enter the wound and begin to multiply. The bacteria may come from the surrounding skin, the external environment, or the object that caused the injury.
It is important to clean and protect the wound properly to reduce the risk of infection.
The risk of wound infection is higher if:
- the wound is large, deep, or has a jagged edge
- dirt or foreign particles entered the wound
- the cause of the wound was a bite from an animal or another person
- the cause of the wound was an injury involving a dirty, rusty, or contaminated object
Certain health conditions and environmental factors can also increase the risk of infection. These include:
- diabetes
- poor blood circulation
- a weakened immune system, such as in people living with HIV or those taking immunosuppressant medications
- lack of mobility, for example, in people who spend most of their time in bed
- advancing age — older adults are more at risk of wound infection
- nutrient and vitamin deficiencies
Rarely, incision wounds from surgical procedures can also become infected.
Complications
If a person does not receive treatment for a wound infection, it can spread to other parts of the body, which may lead to serious complications, including:
- Cellulitis is an infection of the deeper layers and tissues of the skin, and it can cause swelling, redness, and pain in the affected area. Other symptoms can include fever, dizziness, and nausea and vomiting.
- Osteomyelitis is a bacterial infection of the bone, and symptoms include pain, redness, and swelling around the infected area. Fatigue and fever are other symptoms that may affect those with osteomyelitis.
- Sepsis is an extreme immune reaction that can sometimes occur when an infection enters the bloodstream. Sepsis can lead to multiple organ failure and is life-threatening. According to the CDCTrusted Source, nearly 270,000 people in the U.S. die each year due to sepsis.
- Necrotizing fasciitis is a rare condition that occurs when a bacterial infection spreads into a tissue called the fascial lining that lies deep beneath the skin. Necrotizing fasciitis is a medical emergency that causes severe skin damage and pain and can spread throughout the body.

When to see a doctor
A person with a wound should seek medical attention if:
- the wound is large, deep, or has jagged edges
- the edges of the wound do not stay together
- symptoms of infection occur, such as fever, increasing pain or redness, or discharge from the wound
- it is not possible to clean the wound properly or remove all debris, such as glass or gravel
- the cause of the wound was a bite or an injury from a dirty, rusty, or contaminated object
Seek urgent medical attention if blood is spurting from the wound or if applying pressure to the wound does not stop the bleeding.
Diagnostic Studies
- Bacterial culture
- Gram stain
- Antimicrobial susceptibility
- Fungal culture
- Blood culture
Treatments & Interventions for Infected Wounds
The following precautions can help minimize the risk of developing infected wounds in at-risk patients and to minimize complications in patients already exhibiting symptoms:
- Prompt and proper wound cleansing to reduce bioburden
- Maintaining proper nutrition and hydration
Approaches to treatment can be broken down by whether the infection is systemic or localized just to the wound area. Systemic treatment often will call for oral antibiotics, the specific type determined by microbiological investigation and local infection control protocols.
Localized infections can often be treated with topical antibiotics. Drainage or debridement may be necessary to remove slough and devitalized tissue, as these slow wound healing and can affect the efficiency of topical antibiotics. Antimicbrobial dressings, including those that use silver technology, may be used to help reduce bioburden. Antibiotics, whether topical or systemic, should only be used under the explicit direction of a physician.

How are wound infections prevented?
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
- Maintain positive pressure ventilation of operating theatre
- Laminar airflow in high-risk areas
- Sterilisation of surgical instruments, sutures etc according to guidelines
Surgical team members educated in aseptic technique
- Staff with infections excluded from duty
- Scrubbing up followed by appropriate sterile attire
Techniques applied to the patient to prevent wound infections include:
- Skin preparation
- Wound cleansing
- Antibiotic prophylaxis
- Good surgical technique.
Antiseptic wound 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 the infection is already established. When deciding on a prophylactic antibiotic consider the following:
- Use an antibiotic based on likely bacteria to cause infection
- An antibiotic should have good tissue penetration to reach wound involved
- Timing and duration of antibiotic – it is important that therapeutic concentrations are reached at the time of the incision, throughout the surgical procedure and ideally a few hours postoperatively.
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 have a major impact on both patient health and health economics.
























