The skin is contaminated with usually harmless bacteria; however, when a wound occurs, there is a possibility that microbes can cause an infection, as the natural protective mechanism of the skin gets broken down. Microbes in the wound are categorized into levels: contaminated, colonized, critically colonized, and infected. Contaminated wounds do not increase bacterial load or cause a clinical effect; colonized wounds contain multiplying microbes, but they do not damage or affect wound healing processes.
Critical colonization happens when the wound moves from containing multiplying bacteria to an infected state with impaired healing; however, there is no invasion of the tissues and no inflammatory response signs. Infection occurs when the bacteria multiply, invade, and damaging tissues, causing a local or systemic response.
The effects of bacterial burden, called bioburden, on the infected wound, are numerous and complex. Bacteria not only compete for the limited nutrients and oxygen present in the wound; they produce endotoxins and exotoxins that destroy normal cellular activities, such as collagen deposition and cross-linking. Failure to recognize the manifestations of the continuum of bioburden conditions leads to prolonged delay of healing and, eventually, sepsis, as well as the continued growth of antibiotic-resistant microorganisms.