What are wound and skin infections?
Wound and skin infections represent the invasion of tissues by one or more species of microorganism. This infection triggers the body's immune system, causes inflammation and tissue damage, and slows the healing process. Many infections remain confined to a small area, such as an infected scratch or hair follicle, and usually resolve on their own. Others may persist and, if untreated, increase in severity and spread further and/or deeper into the body. Some infections spread to other organs and/or into the blood and cause a systemic infection (septicemia).
Skin is the body's largest organ and its first line of defense. Even when it is clean, the surface of the skin is not sterile. It is populated with a mixture of microorganisms called normal flora. This normal flora forms a dynamic barrier that helps to keep other more harmful microorganisms (pathogens) at bay. People may also have pathogens on their skin. At any one time, a certain percentage of the general population will be carriers of a pathogen that displaces some of their normal flora and colonizes locations like the mucous membranes of the nose. Most of the time, normal flora and colonizing pathogens do not cause illness and do not stimulate the immune system. If there is a break in the skin or if the immune system becomes compromised, then any of the microorganisms present can cause a wound or skin infection.
Wounds are breaks in the integrity of the skin and tissues. They may be superficial cuts, scrapes or scratches but also include punctures, burns, or may be the result of surgical or dental procedures. The microorganisms likely to infect them depend on the wound's extent and depth, the environment in which the wound occurs, and the microorganisms present on the person's skin. The skin has three layers: the outer epidermis, the dermis – where many hair follicles and sweat glands are located – and the fatty subcutaneous layer. Below these layers are membranes that protect connective tissues, muscle, and bone. Wounds can penetrate any of these layers, and skin infections can spread into them. Wound healing is a complex process that involves many related systems, chemicals, and cells working together to clean the wound, seal its edges, and to produce new tissues and blood vessels.
Skin and wound infections interfere with the healing process and can create additional tissue damage. They can affect anyone, but those with slowed wound healing due to underlying conditions are at greater risk. Examples of conditions that increase the risk of wound infections include:
- Poor circulation
- Weakened/suppressed immune system (e.g., HIV/AIDS, organ transplant recipient)
- Low mobility or immobility (e.g., confined to bed, paralysis)
When infections penetrate deep into the body into tissues such as bone, or when they occur in tissue that has inadequate circulation, they can become difficult to treat and may become chronic infections.