To detect and identify the bacteria causing an infection of your wound and to help guide treatment of your wound infection
Bacterial Wound Culture
Bacterial Wound Culture
Also Known As
Aerobic Wound Culture
Anaerobic Wound Culture
Formal Name
Culture, wound
This article was last reviewed
on
This article waslast modified
on
April 25, 2018.
At a Glance
Why Get Tested?
Test Preparation Needed?
None
Accordion Title
Common Questions
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How is it used?
A bacterial wound culture is primarily used, along with a Gram stain and other tests, to help determine whether a wound is infected and to identify the bacteria causing the infection.
If a culture reveals that a wound is infected, susceptibility testing is done to determine which antibiotic will inhibit the growth of the bacteria causing the infection. This is often performed automatically as part of the original order on the wound specimen so that antimicrobial susceptibility results can guide appropriate therapy as soon as possible.
A wound culture may also sometimes be ordered for an individual who has undergone treatment for a wound infection to determine whether the treatment was effective. It may also be ordered at intervals for a person who has a chronic infection to help guide further treatment.
If a fungal infection is suspected, then a fungal culture of the wound specimen may be ordered along with the bacterial wound culture. Yeast and some fungi may grow on the same media as bacteria, but many fungi are slow-growing. The media used to recover fungi inhibits bacterial growth and supports fungal growth for several weeks.
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When is it ordered?
This test is primarily ordered when a healthcare practitioner suspects that a wound is infected. Some signs and symptoms of an infected wound may include:
- A wound that is slow to heal
- Heat, redness and swelling at the site
- Tenderness at the site
- Drainage of fluid or pus
- Fever
It may also occasionally be ordered after a person has been treated for a wound infection to evaluate the treatment's effectiveness and may be ordered when indicated to help guide the treatment of a chronic wound infection.
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What does the test result mean?
Laboratory reports for cultures typically name the bacteria identified during the test. A negative culture will usually be reported, for example, as "no growth seen in 5 days" or note the presence of normal skin flora only.
If pathogenic bacteria are identified in the culture, then it is likely that they are the source of the infection. An infection is typically caused by a single type of bacteria, but wounds may have two or more pathogens (aerobes and/or anaerobes) that are contributing to the infection.
If more than three organisms are present, they may not be identified as individual bacterial species and the report may refer to them as "mixed bacterial flora." This may indicate a mixture of normal flora found on the skin and potential pathogens cultured from a wound site that was not cleansed properly before the specimen was taken or from a "dirty wound" such as a motorcycle accident, where material from the road is contaminating the wound.
If there is only normal flora present, then the infection may be due to bacteria normally found on the skin, or the pathogen may have been missed in the sample due to low numbers present, or the infection may be due to another cause.
Very little growth may still be significant, especially when the wound infection is in an area of the body considered to be essentially sterile, such as the eye.
If there are no bacteria recovered in the wound specimen, then there may not be a bacterial infection, or the pathogen was not successfully recovered with the sample and test.
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Is there anything else I should know?
With burn wounds, the type and number of bacteria that grow are correlated to the severity of the infection. When burn tissue specimens have a specific bacterial count above a certain number, then removal of dead tissue (debridement) may be indicated.
Wound culture results may be less predictive of what is causing the infection when a person has already been treated with antibiotics or when a person has a chronic infection.
Typically, if an infection has spread from a wound into the blood and other organs, then the same bacteria or yeast may be detected in the person's blood cultures.
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Why would my healthcare practitioner collect more than one sample?
This may be done to increase the chance of detecting the pathogen or to detect multiple pathogens. It may involve multiple swabs, a combination of swabs, fluid aspiration, and/or tissue biopsy, or distinct aerobic and anaerobic sample collection.
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Once I have been treated, can my infection return?Most infections will resolve, but if there is still damaged tissue present or a break in the skin’s protection, then there is the potential for another infection to occur. In some cases, it may take extended treatment and/or a change in medication to resolve an infection.
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Why might one person get an infection and another person not?
Anyone can get a wound infection, but the risk increases with age and with underlying conditions, such as diabetes, that compromise blood flow or the immune system and/or that inhibit healing.
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I had a boil on my arm and the healthcare practitioner did not do a culture of the material when he drained it. Why not?
In a healthy person, the clinical presentation may give the healthcare practitioner sufficient information to treat the infection. With an abscess or boil, the most important treatment is incision and drainage, and antibiotics may not be required. However, if your wound does not heal or it worsens after drainage, you may have an infection with an organism that requires antibiotic therapy tailored to the specific pathogen. In this case, a wound culture should be done to identify the pathogen and perform susceptibility testing to guide treatment.