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Infection vs. Contamination / Colonization

(make sure to view Product Index: Antimicrobials)

  1. What is the difference between these terms?
  2. How do I know if the wound I'm treating is infected?
  3. Are all wounds infected?
  4. Are swab cultures important?
  5. How are infections treated?

All of these are very relevant questions when one deals with wounds. Let's answer them one by one.

1. What is the difference between infection and contamination / colonization?

The basic difference between these two conditions lies in the concentration of organisms in the wound. An infected wound contains a larger number of microorganisms than a contaminated wound. According to the Agency for Health Care Policy and Research (AHCPR), stage 2, 3 and 4 pressure ulcers should all be considered as colonized with bacteria. Proper wound cleansing and debridement should prevent bacterial colonization from proceeding to the point of clinical infection. A contaminated wound will heal, an infected wound will not.

2. How do I know if the wound I'm treating is infected?

There are many tools that you have at your disposal to determine if an infection is present. To begin with, you should assess the clinical picture of this patient and his / her wound. Is the patient febrile? Are the vital signs normal or abnormal ? Does the wound appear red and swollen ? Is there purulent drainage or a foul odor ? Is the area around the wound warm to the touch as compared to nearby skin or skin on the opposite extremity? Is bone exposed (this could indicate osteomyelitis)?

In addition, there are many laboratory tests to determine whether an infectious process is occurring. These include: white blood cell count (WBC), erythrocyte sedimentation rate (ESR), c-reactive protein, x-ray examination, deep tissue culture (not swab), nuclear medicine testing (gallium, technetium and indium scans) and blood cultures.

There entire picture must be evaluated carefully. An abnormally high WBC without the clinical appearance of infection could indicate a false test, an infection occurring someplace else (such as a urinary tract infection) or another disease process altogether.

3. Are all wounds infected?

No, but you should consider all wounds as being contaminated with microorganisms. A contaminated wound will heal, an infected wound will not. Wound exudate contains bacteria killing enzymes that will help prevent an infection. Proper cleansing, debridement and maintaining of a moist wound environment will all create an condition that lessens the chance of infection.

4. Are swab cultures important?

As stated in the AHCPR guidelines, swab cultures do not effectively reveal the infecting organism. Swab cultures only collect the surface contaminating organisms. Tissue biopsy and culture, fluid aspiration cultures and possible bone biopsy are better alternatives for culturing the infecting organism. Note: the AHCPR guidelines state that osteomyelitis is detected in 69 percent of the cases where the WBC, ESR and plain x-rays were all positive, therefore, the need for an invasive bone biopsy may be reduced.

5. How are infections treated?

The first item to be discussed is infection control. We must all strive to avoid any type of cross contamination between patients or multiple wounds on the same patient. Hand washing, clean dressing supplies, new gloves and sterile instruments are all required to perform basic wound care. Proper disposal of contaminated waste is governed by the Occupational Safety and Health Administration (OSHA). Also, protect the wound from urine or fecal contamination.

If a wound infection is suspected, notify the proper health care provider on the case immediately. Once an infection is diagnosed, the practitioner may order topical antibiotic flushes, topical antibiotic applications, oral or systemic antibiotics. An incision and drainage (I and D) may be necessary to decompress an abscess or remove devitalized tissue. These protocols will be determined by the extent of infection, infecting organism, medical history of the patient and any medical allergies. According to the AHCPR, one should not use topical antibiotics such as povidone iodine, iodophor, sodium hypochlorite [Dakin's Solution], hydrogen peroxide or acetic acid to reduce bacteria in wound tissue. These products have been shown to be cytotoxic and inhibit granulation tissue.


Author Dr. Allan D. Freedline and Dr. Tamara D. Fishman.

 


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