Classic teaching is that wounds with more than 105 organisms/gram should be considered infected whereas those with less bacterial count should not. Although studies do show that wounds with bacterial counts greater than this heal more slowly and have a higher rate of infection, a more practical method of diagnosing the infected wound is inspired. As wounds mature, furthermore the types of organisms present in the wound change, the wounds begin to carry a greater level of bioburden, meaning a greater baseline quantity of colonies without being infected.
Conversely, the more virulent bacteria, for example beta-hemolytic streptococcus plus some rare Clostridium species, can certainly cause infection at lower quantitative levels than the more commonly occurring species. Finally, the status of the patient's immune response includes a role in the patient's probability of developing an infected wound. Therefore, the surgeon is inspired to review the look of the wound and also the overall clinical picture when deciding whether a wound is infected.
Although it is essential to note the classic signs or symptoms of infection including erythema, edema, fever as well as an elevated white blood cell count, recent studies trying to establish evidence-based criteria for the determination of a chronic wound infection show that increasing pain, friable granulation tissue, foul odor and wound breakdown are the most sensitive indicators.
Bacteria in chronic wounds often begin a biofilm. It is really an extracellular, polysaccharide-rich matrix in which the organisms are embedded. Within this glycocalyx is a system of channels, like a primordial circulatory system, that allows the bacteria to remain viable with less direct dependence on the host tissue.
Cells in this environment become more sessile and fewer metabolically active. As a result, they're resistance against host immune responses and antibiotic therapy. Biofilms often coat foreign and implanted material, making infections in this setting more difficult to treat, and certain bacteria such as Pseudomonas aeruginosa have a predilection to biofilm production.
History includes information associated with the chronicity from the wound, any changes to the wound appearance, and details that should make the clinician concered about a more invasive bacterial involvement (e.g., pain, fever).
Mitigating factors for example comorbid conditions that could lead to immunosuppression, the use of any immunosuppressive medications, previous radiation in the wound area and the overall functional status of the patient are essential to explore. In addition to some white blood cell count and blood cultures, laboratory tests range from the erythrocyte sedimentation rate and C-reactive protein.
While not specific, in a patient without any recent history of surgery or acute illness, their value is in helping determine the amount of systemic response to a wound and in helping determine the presence of a deep wound infection.
When examining a wound, its depth and width should be measured and a careful inspection and probing should be done. Focus on findings such as erythema at least 5 mm beyond the wound edges, expressed pus, necrotic debris or granulation tissue that is dark, friable or heaped above the wound edges can help to look for the extent of infection.
Foreign bodies such as old strands of gauze should be removed and the presence of underlying foreign material such as sutures or mesh should be ruled out. Care should be come to ensure that wounds overlying osseous structures do not have any exposed bone at their base that indicate the presence of osteomyelitis.
Bacterial cultures can help to make a diagnosis and guide appropriate therapy. In a wound that continues to be appropriately cleaned and eager, a swab of the deeper tissue can give a qualitative notion which bacteria can be found. It does not, however, allow the clinician to quantitate the quantity of bacteria inside the wound. For this, the defacto standard is really a biopsy culture. A punch biopsy is taken and ground right into a liquid state from which serial dilutions are cultured. A measure of colonies per milligram can then be reported.
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