Infection vs. Contamination / Colonization
(make sure to view Product Index: Antimicrobials)
- What is the difference between these terms?
- How do I know if the wound I'm treating is
- Are all wounds infected?
- Are swab cultures important?
- 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
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
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
Author Dr. Allan D. Freedline and Dr. Tamara D. Fishman.