Clinic-based Debridement of Chronic Ulcers Has Minimal Impact on Bacteria

Outpatient-based sharp debridement is considered an important element for the care of a chronic ulcer. Objective. The aim of this study is to evaluate the change in bacterial amounts with sharp debridement in a clinical setting. Materials and Methods. Bacterial autofluorescence, quantitative cultures, semiquantitative cultures, and qualitative speciation were performed predebridement and postdebridement during a single clinic visit. Results. Thirty-six wounds were included in the analysis. The mean patient age was 62 years (range, 27–83 years), and there were 13 (36.11%) women and 23 (63.89%) men with an average body mass index of 33.8 kg/m² (range, 16.7–55.9 kg/m²). Of the 36 patients, 24 (66.67%) had type 2 diabetes and 19 (52.78%) had a prior history of lower extremity amputation. Majority of the ulcers were diabetic neuropathic (27, 75%); the most common location was on the plantar aspect of the foot (14, 41.67%) with a mean ulcer duration of 10 months (range, 1–36), mean ulcer area of 6.3 ± 12.8 cm² (range, 0.18–62.06 cm²), and mean volume of 2.2 ± 4.4 cm³ (range, 0.05–9.66 cm³). There was no statistically significant difference in bacterial autofluorescence between the predebridement (4.15 ± 8.82) and the postdebridement (4.65 ± 9.48) images (P = .32). There was a statistically significant difference in quantitative culture results between the predebridement (6.7 x 10⁴ ± 1.4 x 10⁶ CFU/cm²) and the postdebridement (1.7 x 10⁴ ± 3.1 x 10⁶ CFU/cm²) cultures (P = .04), although this is not a log reduction. Conclusions. There is no statistically significant difference between the predebridement versus postdebridement semiquantitative culture results or a detectable pattern of change for the most common bacterial species encountered. These results suggest little impact of clinic-based sharp debridement on bacteria.

Sharp debridement is considered one of the fundamental principles for care of a chronic ulcer.^1,2 Sharp debridement is thought to serve multiple functions, including activation of senescent cells, stimulation for the release of growth factors, removal of inflammatory factors, and reduction in bioburden.^3,4 Chronic ulcers harbor planktonic bacteria, which can cause local or systemic infection, as well as colonies of bacteria in the form of biofilm. The clinical impact of biofilm has not yet been clearly elucidated, but it may impair ulcer healing.⁵ Biofilm cannot be detected through traditional culture methods and requires specialized equipment (eg, scanning electron microscopy) and specialized methods (eg, specific handling and processing of samples). Thus, the utility of its detection and relevance in clinical practice is unknown. However, it is understood that bacteria are present on chronic ulcers and play a role in ulcer chronicity.^6,7

Sharp debridement is often performed serially in the outpatient setting and is a component in the standard of care for the treatment of a chronic ulcer. However, the impact of sharp debridement on bacteria in the outpatient setting is not clear. The aim of this study is to evaluate the impact of clinic-based sharp debridement on bacteria utilizing bacterial autofluorescence, quantitative cultures, semiquantitative cultures, and qualitative culture methods.

This is a single site study conducted at an urban wound center located within an academic hospital. Patients presenting to the clinic for a chronic ulcer on the lower extremity (below the knee) were recruited into the study and written informed consent was obtained. In addition, patients did not receive payment for their participation. This study was approved by the Georgetown University Medical Center Institutional Review Board (Washington, DC).

All study activities were performed during a single clinic visit. Eligibility criteria included ulcers without signs of acute ascending infection, patient age between 18 years and 90 years, and patients who required sharp debridement by the surgeons. All demographic information was obtained from the patient’s medical records. If the patient had more than 1 ulcer, the index ulcer was considered the largest. All study-related activities were performed on the index ulcer prior to addressing the other ulcers. A subjective assessment of wound quality, including degree of erythema, edema, drainage, maceration, and wound margins, was made prior to the sharp debridement by the investigators (PJK, CEA, JSS, KKE). Data were captured on a standardized case report form. Sharp debridement was performed using a curette, scissors, and/or surgical blade to remove all devitalized tissue in a standard manner by surgeons until bleeding tissue at the wound base and margins was observed. All wounds were gently cleansed with normal saline prior to debridement. No irrigation was utilized at any point.

Bacterial autofluorescence images were captured utilizing a point-of-care platform (MolecuLight i:X; MolecuLight, Inc, Toronto, Canada). Images of the entire ulcer as well as the surrounding area were taken with the exam room lights off before debridement was performed (predebridement) and after debridement was performed (postdebridement). The device signals the appropriate distance to the ulcer surface at 10 cm to 15 cm for optimal image capture and emits a 405-nm ultraviolet light. The autofluorescence emission reflected from the surface of the ulcer is absorbed by the device at 490 nm to 800 nm wavelength range. The captured image was uploaded to a customized MATLAB (MathWorks Inc, Natick, MA) software interface. The red spectrum was adjusted to a value between 0 nm and 150 nm to mask the relevant red spectrum that isolates any surface bacteria. The shape of the ulcer was traced to standardize the comparison between the pre- and postdebridement image fields. The percent red (pixel intensity) is then calculated by the software, which indicates the presence of bacteria. The investigators were blinded to the pre- and postdebridement images taken with this device.

Bacterial cultures were obtained immediately after the autofluorescence images were taken. A swab sample (Levine’s technique) from the surface of the wound was obtained and placed into a culture tube. This was performed immediately before and after debridement. The culture tube was sent to a single lab (RTLGenomics Inc, Lubbock, TX) for bacterial quantitative, semiquantitative, and qualitative analyses. Bacterial quantitative cultures were prepared and counted as colony forming units (CFUs) per square centimeters (CFU/cm²). Semiquantitative culture results were assigned to the following categories: high (≥ 10⁷), medium (10⁵–10⁷), low (≤ 10⁵), and not detected (0). Qualitative culture speciation was obtained through quantitative polymerase chain reaction ribonucleic acid pyrosequencing method.

An a priori power analysis was performed assuming a 25% reduction in bacterial fluorescence from predebridement to postdebridement. A power of 80% is reached with 32 patients on a 2-sided paired t test with an α = 0.05. Accounting for 10% attrition, a total of 36 patients were recruited for this study. Nonparametric analog of the t test, a Wilcoxon rank sum test of medians, was utilized due to the departure from normality for comparison of pre- and postdebridement for bacterial fluorescence and quantitative culture results. A Fisher’s exact test was utilized for semiquantitative and qualitative data.

Thirty-six patients (36 wounds) were included in the analysis (Table 1). The mean age was 62 years (range, 27–83 years), and there were 13 (36.11%) females and 23 (63.89%) males with a body mass index of 33.8 kg/m² (range, 16.7–55.9 kg/m²). The most common comorbidities included type 2 diabetes (24, 66.67%), prior history of lower extremity amputation (19, 52.78%), and peripheral neuropathy (17, 47.22%). A subjective assessment of the ulcer condition also was collected (Table 2 and continued). The majority of ulcers were classified as diabetic neuropathic (27, 75%). The most common ulcer location was on the plantar aspect of the foot (14, 41.67%), and the mean ulcer duration was 10 months (range, 1–36 months). The mean area was 6.3 ± 12.8 cm² (range, 0.18–62.06 cm²) with a mean volume of 2.2 ± 4.4 cm³ (range, 0.05–9.66 cm³). Subjective clinical evaluation of the wound suggested that an uninfected state for the vast majority of ulcers had a mean wound granulation of 79%, while 88% had no surrounding erythema, 8.3% had malodor, and 1 patient had a superficial scant drop of white viscous fluid. 

There was no statistically significant difference in bacterial autofluorescence between the predebridement (4.15 ± 8.82) and the postdebridement (4.65 ± 9.48) images (P = .32) (Table 3). There was a statistically significant difference in quantitative culture results between the predebridement (6.7 x 10⁴ ± 1.4 x 10⁶ CFU/cm²) and the postdebridement (1.7 x 10⁴ ± 3.1 x 10⁶ CFU/cm²) cultures (P = .04), although there is not a log reduction. There was no statistically significant difference between the predebridement versus postdebridement cultures in the semiquantitative culture results in all categories (high category: no growth; moderate category: 6–2; low category: 10–8; not detected category: 16–24). There was an increase in 11% from a lower category to a higher category and a decrease in 28% from a higher category to a lower category. There was no detectable pattern of change in the qualitative cultures for the most common bacterial species that are identified (Figure). 

Other authors have suggested that surgical debridement may have minimal impact on bacteria in the operating room.⁸ The present results indicate that there is minimal effect of clinic-based debridement on bacterial amounts detected on the surface of ulcers. It is important that the 3 methods utilized to detect bacterial amount (bacterial fluorescence, quantitative cultures, and semiquantitative cultures) be collectively interpreted. Although there was a statistically significant decrease in the quantitative culture results, there was no log reduction in bacterial amount. A decrease in log(s) of bacteria is generally accepted as a standard for detection of a meaningful impact of an intervention. Thus, the authors are not confident that the result of a statistical difference after sharp debridement is consequential. There is a general trend for a decrease in bacterial load from higher bacterial amounts to a lower bacterial amount with sharp debridement, but this is not statistically significant regardless of the predebridement amount of bacteria.

These results should be thoughtfully interpreted. The investigators did not collect data to observe the effect of clinic-based sharp debridement on ulcer healing; the objective of this study was to capture the effect of sharp debridement on bacterial amount at a single point in time. Extrapolation of these results to the larger clinical goal of ulcer healing is not possible with these data. Despite the results, the authors continue to support the accepted practice of regular clinic-based ulcer maintenance debridement to stimulate ulcer healing. The positive effects of sharp debridement may still be beneficial to ulcer healing by other mechanisms, including activation of senescent cells and removal of proinflammatory factors that inhibit or delay healing.

There is evidence to support the practice of clinic-based ulcer maintenance debridement. Cardinal et al⁹ conducted a retrospective subanalysis of 2 large, prospective, randomized, multicenter studies on diabetic foot ulcers and venous leg ulcers, and they reported higher rates of wound healing and closure for those investigative sites that performed sharp debridement more frequently. However, there was no standardization of the degree of debridement performed across the sites.⁹ Williams et al¹⁰ reported that clinic-based sharp debridement increases the rate of healing for chronic venous leg ulcers compared with those who did not receive sharp debridement and interestingly reported no difference in infection rates in this prospective cohort study. Histologically, Blumberg et al¹¹ reported debridement positively impacted cellularity, vascularity, collagen density, and fibrosis, which is related to chronicity of venous ulcers. However, other authors have argued that there is still a paucity of robust evidence regarding the clinical value of sharp debridement.¹²

The present study looks specifically at the effect of sharp debridement on removing bacteria, but the authors cannot comment on the effect of sharp debridement on biofilm. Semiquantitative and qualitative cultures are the most commonly used methods to detect bacteria. These methods do not detect bacteria contained in biofilm. There may be an impact on removing surface biofilm by utilizing sharp debridement, which the investigators were not able to detect. Further, quantitative cultures do not discriminate between biofilm and planktonic bacteria, and a significant counting error is introduced due to the aggregation of the biofilm matrix. Thus, the results do not necessarily reflect any impact of sharp debridement on biofilm. Wolcott et al¹³ reported a “time-dependent therapeutic window” of opportunity for antimicrobials and advocates for debridement of biofilm to create this window. This study examined the impact of timing of antimicrobial treatments in different models (in vitro, animal, and clinical). Only 3 patients were included in the clinical portion of the study.¹³ The present data do not necessarily support the findings of Wolcott et al,¹³ as the data herein suggest there is no effect on bacterial amount with sharp debridement. Again, the investigators were not looking specifically at biofilm, thus there may be little correlation with Wolcott et al.¹³ However, there is evidence that suggests biofilm may be present and deeply imbedded around vessels.¹⁴ Clinic-based sharp debridement is limited by the ability to maintain hemostasis and control pain. Thus, deeper sharp debridement is not generally performed in the clinic setting. Therefore, studies that report the value of clinic-based sharp debridement and its impact on biofilm may not be accurate.

Further, the investigators observed similar trends of no meaningful reduction of bacteria from pre- and postdebridement for bacterial autofluorescence, quantitative, and semiquantitative culture results. There are prior animal models, feasibility studies, and observational reports utilizing the utility of the bacterial autofluorescence device.^15-17 The present study is the first to assess the impact of sharp debridement and the results of this technique against different bacterial culture methods in the outpatient setting. Bacterial autofluorescence is a novel technology that allows for rapid point-of-care assessment of bacteria on the surface of ulcers. Traditional culture techniques require microbiological assays, which take several days to receive the results. This device is attached to an iOS platform (Apple Inc, Cupertino, CA) to capture images in real time. This may be helpful in determining whether or not there is heavy bacterial load that may be contributing to ulcer chronicity. Further, this technology may be helpful to guide the clinician on where the bacteria may be clustered, which may help the clinician on where to debride or redebride. This technology is not able to speciate bacteria, which is necessary for targeted antibiotic therapy. However, due to its high utility and based on the present results on its reliability, this device may be a useful tool in daily practice.

Bacteria on the surface of an ulcer may be different than those detected in the deeper tissue, which may be the more virulent bacteria that lead to infection. Sibbald et al¹⁸ reported no effect of a topical antimicrobial on quantitative cultures at deeper levels despite the impact on superficial bacteria as detected through semiquantitative swab methods. Thus, the ultimate clinical outcome (ulcer closure) may not be related to the data presented in this study, which were limited to assessing bacteria on the surface of the ulcer. Ratliff et al¹⁹ reported no correlation between quantitative bacteria levels on the surface of the ulcer and ulcer healing for clinically uninfected wounds. In addition, the authors recently published the results of a 30-day clinical outcomes study after serial operative debridements were performed.²⁰ These data suggest that positive semiquantitative culture at the time of operative ulcer coverage or closure had no impact in postoperative infection and dehiscence rates except when coagulase-negative Staphylococcus aureus was detected. The relationship between bacteria and ulcer healing needs to be further elucidated, and the present study does not provide additional information that would help establish this relationship.

There are several limitations to this study. Although an attempt was made to standardize the mechanism of obtaining cultures, there may have been slight variations in the technique. The technique of obtaining cultures and culturing methods have been criticized and debated in the literature.^21,22 The investigators utilized a sampling of a mixture of tissue and fluid rather than just tissue. Variations in technique may have affected the bacteria detected. Thus, the results may reflect this issue. One patient enrolled in the current study had a scant amount of white viscous fluid and may have been infected. However, there were no other clinical signs of infection, and antibiotics were not prescribed for this patient. Further, the culture results from this patient did not show heavy growth of bacteria; thus, this patient was included as part of the analysis. Also, the study examines the effect of sharp debridement at a single time point. Although it is likely that patients included in this study had prior regular debridements, this information could not be confirmed. There may be a cumulative effect of serial debridement over time that may influence bacterial amount. Longitudinal studies with multiple sampling over time would be needed to answer this question. It also is important to note that none of the patients in this study had heavy bacterial growth. In the environment of heavy bacterial growth, the effect of sharp debridement may be detectable.

There is clear consensus among wound experts that clinic-based sharp debridement is a fundamental aspect of chronic ulcer care. However, the data herein suggest the impact of sharp debridement at a single time point may have minimal effect on bacterial amount. It is more likely that sharp debridement induces and triggers a cascade of other events that speed the rate of healing that may be independent of reducing bacterial amount. These data should be carefully considered along with other studies in determining the value of clinic-based sharp debridement. 

Affiliations: Department of Plastic Surgery, MedStar Georgetown University Hospital, Washington, DC; Georgetown School of Medicine, Washington, DC; and University of Arizona School of Medicine, Tucson, AZ

Correspondence: Paul J. Kim, DPM, MS, Associate Professor, Department of Plastic Surgery, MedStar Georgetown University Hospital, 3800 Reservoir Road NW, Washington DC, 20007;
paul.j.kim@gunet.georgetown.edu

Disclosure: MolecuLight, Inc (Toronto, Canada) provided funding for processing of the bacterial samples. No other funding was provided. This company provided the bacterial fluorescence device as well as technical support for this platform. MolecuLight, Inc was not involved in the study design, analysis, or the writing of this manuscript. The authors have no financial affiliation with MolecuLight, Inc.