Quantitation of Bacteria in Clean, Nonhealing, Chronic Wounds
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Address correspondence to:
George T. Rodeheaver, PhD
Plastic Surgery Research
University of Virginia Health System
Box 801351
Charlottesville, VA 22908-1351
Phone: 434-924-2126
E-mail: grt3s@virginia.edu
Abstract: Quantitative swabs were obtained from 30 clean, chronic wounds on 30 different patients during one visit. The number of organisms and the predominant organism were determined. All samples were processed under both aerobic and anaerobic conditions. Nineteen (63%) of the 30 clean wounds had bacterial levels that were ≥ 105 cfu/cm2. There was no correlation between ≥ 105 cfu/cm2 and delayed wound healing. The most frequently isolated predominant organism was Staphylococcus aureus. In these clean, chronic wounds, an obligate anaerobic organism was identified as predominant or co-predominant in only 2 (6.7%) of 30 wounds.
The influence of bacteria on wound healing is complex and controversial. It is accepted that all open, chronic wounds are colonized with bacteria. Most physicians believe that if the wound does not display traditional signs of infection, then the bacteria are not interfering with the healing process. As new information is being presented, many physicians are starting to believe that high levels of bacteria may inhibit healing in the absence of traditional signs of infection.1,2
The level of bacteria that inhibits wound healing but does not display the standard clinical signs of infection has been termed “critical colonization.”3 In this situation, additional criteria are required to diagnose covert infection.4 Gardner et al5 recently assessed the validity of these additional criteria, which include serous exudate, foul odor, discolored or friable granulation tissue, and delayed healing or wound deterioration. They also performed quantitative biopsies and used Robson’s6 definition of greater than 100,000 (> 105) organisms/g of tissue as being infected. Eleven of the 36 (31%) wounds in their study were infected; 91% of those wounds contained necrotic tissue. For these 11 infected wounds not displaying traditional signs of infection, 80% demonstrated delayed healing and friable granulation tissue.
Unfortunately, quantitative tissue biopsy procedures are not available to most clinicians. A procedure that is more readily available is the quantitative swab technique.7 Using this technique, Bill et al,8 quantitated the level of bacteria in 38 clean, nonhealing, chronic wounds that showed no classical clinical signs of infection. Tissue biopsies showed that 74% of these nonhealing, clean wounds contained > 105 organisms/g of tissue. The quantitative swab technique detected 79% of these infected wounds. With this quantitative information, the wound care plan was altered to focus on reducing the level of bacteria in these wounds, which resulted in healing.
The use of quantitative bacteriology to direct a wound care program is limited by the technical difficulties and expertise required to process the samples. It would be significantly beneficial to wound care providers if a simple diagnostic test were available to document if a clean, nonhealing wound contained > 105 bacteria/g of tissue. In the development of such a diagnostic test, it is necessary to know whether anaerobic organisms play a significant role in the number of bacteria present in clean, nonhealing wounds. The purpose of this pilot study was to quantitate the number of aerobic and obligate anaerobic organisms in a small number of clean, nonhealing wounds.
Materials and Methods
This study was conducted under a protocol approved by the University of Virginia’s Institutional Review Board for Health Sciences Research.
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