Burn Wound Biopsies Research Articles

Iterative refinement of a histologic algorithm for burn depth categorization based on 798 consecutive burn wound biopsies

IntroductionOur group previously reported a burn biopsy algorithm (BBA-V1) for categorizing burn wound depth. Here, we sought to promulgate a newer, simpler version of the BBA (BBA-V2). MethodsBurn wounds undergoing excision underwent 4 mm biopsies procured every 25 cm2. Serial still photos were obtained at enrollment and at excision intraoperatively. Burn wounds assessed as likely to heal by 21 days were imaged within 72 h of injury and at 21 days. A sample of 798 burn wound biopsies were classified by both BBAV1 and BBAV2 algorithms. For nonoperative burn wounds, the proportion of healing versus nonhealing pixels at 21 days after injury were compared. ResultsThe 798 biopsies were classified by BBAV1 as 24% SPT, 47% DPT, 28% FT and by BBAV2 as 3% SPT, 67% DPT, and 30% FT (p < 0.0001). Overall, the proportion of biopsies whose wound reclassification changed from a nonoperative to operative pathway was 21% (95% CI: 18–24%). Nonoperative wounds judged at injury as being SPT contained 12.8 million pixels. Repeat 21-day imaging revealed 11.3 million healed pixels (accuracy = 89.6% (95% CI: 89.59–89.62)). ConclusionsBBA-V2 was associated with a significantly higher concordance with visual assessment for burn wounds clinically judged as deep partial and full thickness.

Epidemiological and bacteriological profile of sepsis in burns patients: A report from tertiary care hospital, India

Background: Burns are one of the most prevalent and mortifying forms of trauma. Patients burn with significant thermal injury require immediate intensive care unit (ICU) care to minimize morbidity and mortality. Burns patients are generally more predisposed to sepsis because of two main reasons, i.e., burn wound infection and catheter-related bloodstream infection (CRBSI). Due to extensive skin barrier disruption and an alteration in the cellular and humoral immune responses burn wounds has a much higher incidence of sepsis as compared to other forms of trauma. Aims and Objectives: The present study was undertaken to study the bacteriological profile and sources of sepsis in burns patients and their antimicrobial susceptibility pattern. Materials and Methods: It is a prospective observational study conducted in the Department of Burns, Plastic and Maxillofacial Surgery, ICU and Department of Microbiology of a tertiary care hospital, Uttar Pradesh, India, between January 2020 and June 2022. Adult patients with 30–70% of total body surface area burns with central venous catheter (CVC) inserted during ICU admission were enrolled in the study. The presence of clinical sepsis in the burn patients was evaluated using the American Burn Association Sepsis criteria. For all patients with suspected clinical sepsis, paired blood cultures were collected simultaneously; one from the CVC and another from a peripheral site and were sent for bacteriological culture. Blood culture samples were processed as per standard procedures. CRBSI was defined if the same organism was isolated in paired blood cultures. Burn wound biopsy was sent for quantitative culture and 105 organisms/g of tissue were considered significant. Results: In the present study, the overall incidence of clinical sepsis was 28.4% (39/137), out of which 48.7% of cases were found to be due to CRBSI and the most common organism involved was Klebsiella spp. (42.1%), 33.3% of cases were due to burn wound sepsis and the most common organism involved was Pseudomonas spp. (61.5%); and 18.0% of cases were those in which no known source could be found. Possible explanations for these cases could be sepsis without bacteremia due to endotoxins and Gram-negative endotoxemia. Conclusion: To find out microorganisms causing burn wound infection by culture and provide suitable antibiotics according to their antibiotic sensitivity patterns helping us in managing these infection and decreasing overall morbidity and mortality in burn patients.

52 Refinement of a Histologic Algorithm for Burn Depth Categorization Using 1142 Consecutive Burn Wound Biopsies

IntroductionOur group previously reported a theoretical burn biopsy algorithm (BBA-V1) for the categorization of burn wound depth based on histologic analysis, and informed it with the largest series of burn wound biopsies in the literature. That iteration of the BBA resulted in clinical misclassification rates consistent with past literature. Since our last report of that process, we have refined the algorithm with new criteria and a larger repository of burn wound biopsies. Here, we sought to promulgate this newer, simpler version of the BBA (BBA-V2).MethodsThis was an IRB-approved, prospective, multicenter study. Patients with burn wounds assessed by burn experts as requiring excision and autograft underwent 4mm biopsies procured every 25cm2. Serial still photos were obtained at enrollment and at excision intraoperatively.Using H&E with whole slide scanning, a board-certified dermatopathologist assessed each burn biopsy. The criteria used for categorization of burn wound depth in BBA-V1 were: 1) proportion of necrotic adnexal structures, and 2) presence/absence of each of epidermis, papillary dermis, and reticular dermis. The criteria used for BBA-V2 were: 1) magnitude of reticular dermal degeneration, 2) proportion of necrotic adnexal structures, and 3) magnitude of vessel thrombosis.Biopsy pathology results were correlated with still photos by 3 burn experts for consensus of final burn depth diagnosis. Superficial partial thickness (SPT) wounds were considered to be burn wounds likely to have healed without surgery, while deep partial thickness (DPT) and full thickness (FT) were considered unlikely to heal by 21 days.ResultsThe development of BBA V-1 was previously informed by 66 subjects with 117 wounds and 816 biopsies, and resulted in wound categorizations as follows: SPT (20%), DPT (43%), and FT (37%). Therefore, according to BBA-V1, 20% of burn wounds were incorrectly judged as needing excision and grafting by the clinical team. The overall cohort was enlarged to 162 subjects with 294 wounds and 1142 biopsies. The most recent 838 burn wound biopsies were then re-reviewed and re-categorized according to the new BBA-V2 criteria and algorithm. Under BBA-V2, 3% of all burn wound biopsies were categorized as superficial partial thickness, 69% were categorized as deep partial thickness, and 29% were categorized as full thickness.ConclusionsOur study demonstrates that by adding dermal degeneration severity and vessel thrombosis to our previous criterion of adnexal structure necrosis, BBA-V2 had a much higher rate of concordance with visual clinical assessment for burn wounds clinically judged as needing surgical excision. This study serves as the largest analysis of burn biopsies by modern day burn experts.

Use of 816 Consecutive Burn Wound Biopsies to Inform a Histologic Algorithm for Burn Depth Categorization

Burn experts are only 77% accurate when subjectively assessing burn depth, leaving almost a quarter of patients to undergo unnecessary surgery or conversely suffer a delay in treatment. To aid clinicians in burn depth assessment (BDA), new technologies are being studied with machine learning algorithms calibrated to histologic standards. Our group has iteratively created a theoretical burn biopsy algorithm (BBA) based on histologic analysis, and subsequently informed it with the largest burn wound biopsy repository in the literature. Here, we sought to report that process. This was an IRB-approved, prospective, multicenter study. A BBA was created a priori and refined in an iterative manner. Patients with burn wounds assessed by burn experts as requiring excision and autograft underwent 4 mm biopsies procured every 25 cm2. Serial still photos were obtained at enrollment and at excision intraoperatively. Burn biopsies were histologically assessed for presence/absence of epidermis, papillary dermis, reticular dermis, and proportion of necrotic adnexal structures by a dermatopathologist using H&E with whole slide scanning. First degree and superficial second degree were considered to be burn wounds likely to have healed without surgery, while deep second- and third-degree burns were considered unlikely to heal by 21 days. Biopsy pathology results were correlated with still photos by five burn experts for consensus of final burn depth diagnosis. Sixty-six subjects were enrolled with 117 wounds and 816 biopsies. The BBA was used to categorize subjects' wounds into four categories: 7% of burns were categorized as first degree, 13% as superficial second degree, 43% as deep second degree, and 37% as third degree. Therefore, 20% of burn wounds were incorrectly judged as needing excision and grafting by the clinical team as per the BBA. As H&E is unable to assess the viability of papillary and reticular dermis, with time our team came to appreciate the greater importance of adnexal structure necrosis over dermal appearance in assessing healing potential. Our study demonstrates that a BBA with objective histologic criteria can be used to categorize BDA with clinical misclassification rates consistent with past literature. This study serves as the largest analysis of burn biopsies by modern day burn experts and the first to define histologic parameters for BDA.

136 Use of 816 Consecutive Burn Wound Biopsies to Inform a Histologic Algorithm for Burn Depth Diagnosis

Abstract Introduction Burn experts are only 77% accurate when subjectively assessing burn depth, leaving almost a quarter of patients to undergo unnecessary surgery or conversely suffer a delay in treatment. To aid clinicians in burn depth assessment (BDA), new technologies are being studied with machine learning algorithms calibrated to histologic standards. Our group has iteratively created a theoretical burn biopsy algorithm (BBA) based on histologic analysis, and subsequently informed it with the largest burn wound biopsy repository in the literature. Here, we sought to report that process. Methods This was an IRB-approved, prospective, multicenter study. A BBA was created a priori and refined in an iterative manner, resulting in the current state of the algorithm seen in Figure 1. Patients with burn wounds assessed by burn experts as requiring excision and autograft underwent 4mm biopsies procured every 25cm2. Serial still photos were obtained at enrollment and at excision intraoperatively. Burn biopsies were histologically assessed for presence/absence of epidermis, papillary dermis, reticular dermis, and proportion of necrotic adnexal structures by a dermatopathologist using H&amp;E with whole slide scanning. First degree and superficial 2nd degree were considered to be burn wounds likely to have healed without surgery, while deep 2nd and 3rd degree burns were considered unlikely to heal by 21 days. Biopsy histopathology results were correlated with still photos by 3 burn experts for consensus of final burn depth diagnosis. Results Sixty-six subjects were enrolled with 117 wounds and 816 biopsies. The BBA was used to categorize 100% of subjects into 4 categories: 7% of burns were categorized as 1st degree, 13% as superficial 2nd degree, 43% as deep 2nd degree, and 37% as 3rd degree. Therefore 20% of burn wounds were incorrectly judged as needing excision and grafting by the clinical team. As H&amp;E is unable to assess the viability of papillary and reticular dermis, with time our team came to appreciate the greater importance of adnexal structure necrosis over dermal appearance in assessing healing potential. Conclusions Our study demonstrates that a BBA with objective histologic criteria can be used to categorize BDA with clinical misclassification rates consistent with past literature. This study serves as the largest analysis of burn biopsies by modern day burn experts and the first to define histologic parameters for BDA.

C1 Inhibitor Administration Reduces Local Inflammation and Capillary Leakage, Without Affecting Long-term Wound Healing Parameters, in a Pig Burn Wound Model.

Burns induce a boost in local and systemic complement levels as well as immune cell infiltration in the burn wound, which may negatively affect wound healing. In this study, the effects of long-term treatment with complement inhibitor C1 esterase inhibitor (C1inh) on post-burn inflammation and wound healing parameters were analyzed in time up to 60 days post-burn. Burned pigs were treated either with or without C1inh up to 15 days post-burn. Burn wound biopsies and blood were collected at different time points up to 60 days post-burn. Thereafter, complement in blood as well as complement and immune cells in the wound, capillary leakage, necrosis, reepithelialization and wound contraction were quantified. No significant differences in complement C3 blood levels were observed at any time point between C1inh-treated and control pigs. In the wound, complement C4 levels were significantly lower in the C1inh group than in controls at day 3-6 and 21-30 post-burn. Similarly, C3 levels, neutrophil and macrophage infiltration in the wound were, although not statistically significant, reduced in C1inh-treated pigs at day 9-14 post-burn. No differences in lymphocyte infiltration in the wound were found between C1inh and control pigs. C1inh-treated pigs also showed reduced capillary leakage. Despite these effects, no significant differences in the long-term wound healing parameters necrosis, reepithelialization and wound contraction were observed between C1inh and control pigs. In pigs, 15 days of C1inh treatment after burn, leads to a reduction in local inflammation and capillary leakage in the burn wound without affecting long-term wound healing parameters.

Delivery of silver sulfadiazine and adipose derived stem cells using fibrin hydrogel improves infected burn wound regeneration.

Infection control is necessary for improved burn wound regeneration. In this study contact burn wounds were induced on the dorsum of the rats and were infected with Pseudomonas aeruginosa (107cfu/ml of saline) and left overnight (12–14 hours) to establish the infection. After 12 hours, the wounds were treated with PEGylated fibrin hydrogel containing 50 mgs of silver sulfadiazine (SSD) loaded chitosan microsphere (SSD-CSM-FPEG). On day 9, SSD-CSM-FPEG treated burn wounds further received adipose derived stem cell (5×104 ASCs cells/ml) embedded in PEGylated fibrin hydrogel. Wounds were assessed for the healing outcomes such as neovascularization, granulation tissue formation, wound closure and collagen maturation. Analysis of bacterial load in the burn wound biopsies, demonstrated that SSD–CSM-FPEG significantly reduced bacterial infection, while overt infection was still observed in the untreated groups on day 14. Sequential treatment of infected wounds with SSD–CSM-FPEG followed by ASC-FPEGs (SSD-CSM-ASC-FPEG) significantly reduced bacterial colonization (9 log reduction) and pro-inflammatory cytokine (TNF-α) expression. A significant increase in neovascularization markers; NG2 and vWF was also observed. Histological analysis indicated the wounds treated with SSD-CSM-ASC-FPEG increased amount of dermal collagen matrix deposition, a thicker granulation tissue on day 21 and more mature collagen on day 28. This work demonstrates that the sequential treatment of infected burn wounds with SSD-CSM-FPEG followed by ASC-FPEG reduces bacterial infection as well as promotes neo-vascularization with improved matrix remodeling.

Probing endogenous collagen by laser-induced autofluorescence in burn wound biopsies: A pilot study.

The focus of the current study was to interrogate the predictive potential of laser-induced autofluorescence (LIAF) by objectively assessing collagen synthesis in burn wound granulation tissues ex vivo. Prior grafting, granulation tissues (20 samples) following burn injury were collected from 17 subjects of age range 18 to 60 years with patient/donor consent and the corresponding autofluorescence spectra were recorded at 325 nm He-Cd laser (≈2 mW) excitations. The resulting endogenous collagen intensity from the above tissue samples was computed by normalizing the nicotinamide adenine dinucleotide levels. In addition, the hydroxyproline content was also estimated biochemically from the same granulation tissues. A comparative assessment of both LIAF and biochemical estimations for endogenous collagen by hydroxyproline resulted in strong positive correlation among them. The above relevant observations suggest that LIAF is equally informative as that of biochemical estimations, in evaluating endogenous collagen content in wound granulation tissues. Thus, it can be concluded that LIAF has the predictive potential, as a noninvasive objective tool to measure the endogenous collagen levels in wound biopsy tissues and provide complementary data conducive for making clinical decisions.

Neutrophil extracellular traps coincide with a pro-coagulant status of microcirculatory endothelium in burn wounds.

Burn-induced tissue loss is partly related to secondary expansion of necrosis into vital dermis neighboring the initial burn injury. An important factor herein is the severe loss of perfusion of the burn wound, probably caused by microvascular damage induced by the intense local inflammatory responses as well as burn-induced hypercoagulation. We hypothesize that the formation of neutrophilic extracellular traps (NETs) play an important role in this. The purpose of this study was to investigate postburn intravascular thrombosis, NETs formation and the coagulant state in the microvasculature of burns in both animal models and patients. We used two in vivo burn wound models: rats and pigs. In rats, the entire wound was excised at day 14 postburn and in pigs burn wound biopsies were collected at different time points up to 60 days postburn. To confirm the data in patients, eschar from the burn wound was obtained from burn wound patients at different time points after wounding. The number of intravascular thrombi, the presence of intravascular NETs and the number of tissue factor (TF) positive blood vessels in the burn wound was determined. In rats, a significant increase in intravascular thrombi and TF expression was observed 14 days postburn, that in majority coincided with NETs. In pigs, a significant increase in intravascular thrombi and TF expression was found over time up to 60 days postburn, that in majority coincided with NETs too. Also in eschar of burn wound patients, a significant increase in intravascular thrombi was noted, that in majority coincided with NETs, already 0.5 days postburn and remained elevated up to 46 days postburn. This study shows the presence of NETosis in microcirculatory thrombosis of burn wounds and a switch in the microcirculatory endothelium toward a procoagulant phenotype.

The Local and Systemic Inflammatory Response in a Pig Burn Wound Model With a Pivotal Role for Complement.

In patients with burns, a massive inflammatory response is induced which negatively affects the healing process of the burn wound and additionally exerts systemic effects. An important factor herein is the complement system. Here we analyzed the effects of burns on complement and inflammatory cells both locally and systemically after burn in time in a pig burn wound model. In burned pigs, burn wound biopsies and blood were collected up to 60 days after burn. Complement in blood as well as complement and inflammatory cells in the burn wound and several organs were determined. In the blood, C3 was significantly increased after 9 to 60 days, whereas C4 after 21 to 30 days after burn. In the burn wound, C3 levels were significantly increased after 9 days and C4 after 3 days, whereafter both declined after 21 and 9 days, respectively. Neutrophils, macrophages, and lymphocytes were significantly increased in the burn wound after 3 days, all declined after 21 days after burn. In the heart, at 60 days after burn, an increase of neutrophils and macrophages was observed, mainly in the right atrium. In contrast to the heart, the inflammatory cell infiltrates in the lungs, liver, and kidney of burned pigs were lower than in control pigs. In pigs, following burn there is a prolonged increase in complement levels both in the burn wound and the blood and increased inflammatory cell infiltrate in the burn wound and the heart. However, complement levels in the burn wound and in the blood seem not to be correlated in time.

Microbiological and quantitative analysis of burn wounds in the burn unit at a tertiary care hospital in Kashmir

Background: The burn wound represents a susceptible site for opportunistic colonization by organisms of endogenous and exogenous origin. The present study was undertaken to analyze the microflora of burn wounds of the burn patients from a tertiary care hospital in Kashmir, India. Materials sand Methods: The study included all patients with acute burns admitted from January 2010 to December 2011 (2 years). The standard techniques, as practiced during collection of microbiological specimens, were used during wound swab/biopsy collection. Results: 74.19% of swab cultures yielded single isolates. On swab culture, Pseudomonas aeruginosa was the commonly isolated organism (46.86%). Staphylococcus aureus was the most common isolate isolated during 1st postburn week (30.86%). 258/288 (89.58%) blood cultures were sterile. 8/58 (13.79%) blood cultures were positive during the second postburn week. S. aureus was the most common organism grown on blood culture (44.44%). P. aeruginosa was mostly sensitive to polymyxin B (86.0%), amikacin (40.0%), and ciprofloxacin (37.3%), respectively. S. aureus was most commonly sensitive to linezolid (85.0%) and vancomycin (78.8%%) whereas Acinetobacter spp. was sensitive to polymyxin B (65.3%), piperacillin/tazobactam (44.9%), and amikacin (38.8%). Patients (27.27%) who showed local signs of burn wound infection and positive blood culture were subjected to burn wound biopsy. 93.33% of patients who had counts >105 colony-forming unit/g of tissue showed significant association with local signs of burn wound infection and positive blood culture for any organism. Conclusion: The microbiological surveillance of burn wounds needs to be continued for a rational antibiotic policy and prevention of emergence of resistant organisms. Burn wound biopsy culture is an effective tool for quantitative analysis of burn wounds; however, subjecting this biopsy to histological examination is more predictable of burn wound infection and its correlation with burn wound sepsis.

The Correlation Between Time to Skin Grafting and Hypertrophic Scarring Following an Acute Contact Burn in a Porcine Model

One sequelae of burn injury remains the development of hypertrophic scarring. This appears more likely when the healing has been prolonged. Early excision of deep dermal burns and subsequent split skin grafting (SSG) may provide a more favorable result. The optimal timing of grafting for deeper dermal burns remains controversial. This study sought to establish evidence for the optimal grafting time using a porcine model. Five Large White female pigs were exposed to four contact burn injuries for duration of 20 seconds at 92°C. Each site was randomized to a treatment arm: dressing only as the control, SSG day 3, SSG day 14, and SSG day 21. Burn wound biopsies were obtained at days 0, 3, 14, 21, and 99 after the burn injury, together with microbiological swabs. Digital photographs were taken to assess scarring using the Vancouver scar scale. All biopsies were subject to histological and immunohistochemical analysis. Vancouver scar scale scores and histopathological analysis indicated that areas grafted on day 3 had the least fibrosis and scarring (P = 0.031). There was a strong correlation between the histological evaluation of the degree of fibrosis and α-smooth muscle actin levels (r = .60, P = .014). A greater degree of fibrosis was observed in the presence of infection (P = .028). Sites grafted on day 3 consistently exhibited the best clinical and histological scar outcome. The increased fibrosis observed in delayed grafting may have been be related to progression of burn depth and infection. These results suggest that early grafting of deep dermal burns may be preferential.

Changing pattern of fungal infection in burn patients

Invasive fungal burn wound infection is an important emerging cause of late onset morbidity and high mortality in patients with major burns. Following a pilot study done in our unit in 1 year, i.e. January 2008–March 2009 in 71 patients where 28% (20 patients) of the burn wound biopsies from suspected cases showed fungal wound invasion (FWI), a detailed study was planned in order to study the epidemiology of fungal infection in burns in our unit wherein routine wound biopsies in 100 patients were sent on 7th, 14th and 21st postburn day over a one year period (July 2009–June 2010). 12 patients (12%) were diagnosed with FWI on culture. This was then followed by another study in a 9 month period (July 2010–March 2011) when wound samples for only 36 patients in whom there was clinical suspicion of fungal infection were sent. 16 of these patients were diagnosed with fungal wound invasion (FWI) thus establishing an incidence of 44% from suspected cases. These studies showing the increase in fungal infection in our unit have therefore made us wiser, increased our awareness and our accuracy in diagnosing this uncommon infection in extensive burns where patient is not only severely immunocompromised but also has many other risk factors making them more vulnerable to fungal invasion. Another glaring fact which emerged from these studies was the rising incidence of nonalbicans Candida infection compared to Candida albicans, especially C. tropicalis and C. krusei which are more severe in nature and associated with a higher mortality. This signifies that there is a shift of FWI in burns from commensal organism, i.e. C. albicans to pathogenic nosocomial organisms, i.e. C. nonalbicans.

Are Fibrocytes Present in Pediatric Burn Wounds?

Objective of the study is to investigate for the presence of fibrocytes, a leucocyte found at sites of injury with fibroblast-like properties, within pediatric burn wounds. Seventy 3 mm punch biopsies were taken from 53 burn wounds in 33 children between 7 months and 15 years of age at the time of planned operative debridement and grafting. After fixation and sectioning, immunohistochemistry (IHC) staining was performed for CD34, pro-collagen I, alpha smooth muscle actin, transforming growth factor beta1 and Leucocyte Specific Protein-1 (LSP-1). The presence of fibrocytes was confirmed by double immunofluorescence staining with antibodies to CD34 or LSP-1 with pro-collagen I. CD34 positive cells were present in all burn wound biopsies. Using IHC staining, in 18 patients cells positive for CD34 and pro-collagen I were identified; in 17 patients, cells positive for CD34 and alphaSMA and in 17 patients also cells positive for LSP-1 and pro-collagen I. Double immunofluorescence for CD34/pro-collagen I and LSP-1/pro-collagen I confirmed the presence of fibrocytes in specimens from 17 of 18 patients positive for these markers on IHC. Of the 17 patients whose burn wounds were complicated by hypertrophic scarring, fibrocytes were identified in 88% (n = 15) compared with 18% of those without hypertrophic scarring (P < .001). This study represents the first report of the presence of fibrocytes in acute pediatric burn wounds. These cells appear to be involved in the local response to burn wound injury and may correlate with the later development of hypertrophic burn wound scarring.

Guidelines for the treatment of venous ulcers

1. Co-chaired this panel2. University of South Florida, Tampa, FL3. Healthpoint Ltd., Fort Worth, TX4. University of California, San Francisco, CA5. University of Texas Medical Branch, Galveston, TX6. University of Cardiff, Cardiff, Wales, UK7. University of Pennsylvania, Philadelphia, PA8. Private practice, Warren, PA9. Private practice, Tamarac, FL10. University of Pittsburgh, Pittsburgh, PA11. St. Louis University, St. Louis, MO, and12. Washington University, St. Louis, MO

Incidence of bacteremia after burn wound manipulation in the early postburn period.

Transient bacteremia associated with burn wound manipulation is considered a frequent occurrence and is commonly cited as an indication for perioperative antibiotic prophylaxis in burn patients. In a prospective clinical setting, blood cultures (BC) were obtained from 19 burn patients at the following intervals: 30 minutes before wound cleansing (WC) or wound excision (WE), 30 minutes after the start of WC or WE, hourly until procedure completion, and 1 hour after completion. Burn wound biopsy for histologic grading and microbial culture was performed after the first BC. Twenty-two WC and 20 WE episodes were evaluated by 67 and 76 BC sets, respectively. Patients had a mean age of 42.8 years and mean burn size of 50% of the body surface area. Three WC episodes (13.6%) and four WE procedures (20.0%) were associated with postprocedure bacteremia. Two patients had both preprocedure and postprocedure bacteremia later attributed to nonburn wound infections. Excluding these cases, the bacteremia rate was 12.5% (9.5% from WC and 15% from WE). Wound biopsy culture and histologic analysis did not predict the occurrence of bacteremia. Current therapy is associated with a lesser incidence of burn wound manipulation-induced bacteremia than reported in prior series. The discordance between wound biopsy and BC results, the absence of positive histology, and the similarity of bacteremia occurrence rates with WC and WE confirm the effectiveness of current techniques of microbial control in burn wounds and question the need for perioperative antibiotic therapy in patients with burns involving less than 40% of the total body surface during the first 10 postburn days.

Quantitative microbiology in the management of burn patients. I. Correlation between quantitative and qualitative burn wound biopsy culture and surface alginate swab culture

The diagnosis and treatment of burn wound infection is commonly determined by clinical impression and the qualitative results of surface swabs. It has been suggested that quantitative bacteriology from burn wound biopsies confirms burn wound infection and improves patient management. Methods for quantitating surface flora have been described, but comparisons with biopsy specimens have been contradictory. The quantitative and qualitative results of 141 pairs of biopsies and surface swabs, from 74 burn patients, were compared. Staph. aureus was the commonest organism isolated (29 per cent of biopsies and 35 per cent of swabs). Recovery of the same set of species from biopsy and swab occurred in 54 per cent of pairs. There was a significant correlation between the bacterial count obtained by biopsy and by surface swab ( P < 0.001), but using various threshold values, the predictive value of the counts obtained by one method to predict the counts obtained by the other was poor. Parallel cultures taken on 18 occasions, showed a significant correlation between bacterial counts obtained from two biopsies or two swabs taken simultaneously ( P < 0.002), but there was wide variation in bacterial densities from the same burn wound at the same time. Recovery of the same set of species from both biopsies occurred in 56 per cent of pairs, and from both swabs in 50 per cent of pairs. The use of quantitative microbiology in burns is limited by the unreliability of a single surface swab or biopsy to represent the whole burn wound.

Quantitative microbiology in the management of burn patients. II. Relationship between bacterial counts obtained by burn wound biopsy culture and surface alginate swab culture, with clinical outcome following burn surgery and change of dressings

The use of quantitative bacteriology in the burns unit has been thought to be efficient in predicting sepsis or graft loss. To examine the relationship between clinical outcome and bacterial densities on and in the burn wound, 69 biopsy/surface swab pairs were collected from 47 patients on 64 occasions, either immediately prior to excision and grafting, or at routine change of dressings. The mean per cent TBSA burn was 16 (range 1–65). There was a significant correlation between log total bacterial count by biopsy with total white cell count and age ( P = 0.028), and a significant negative correlation between total bacterial count by swab with per cent TBSA ( P = 0.006). There was no significant difference in bacterial counts between patients judged to be a clinical success or clinical failure (72h follow-up), either after undergoing excision and grafting, or change of dressings, and no difference in counts between patients with perioperative bacteraemia and those without. With burns > 15 per cent TBSA, a relationship between bacterial counts and subsequent sepsis or graft loss still was not demonstrated. It is suggested that quantitative bacteriology by burn wound biopsy or surface swab does not aid the prediction of sepsis or graft loss.

Updated evaluation of the activity of antibiotics in a burn centre

The results of microbiological tests performed in a burns unit between January 1989 and December 1990 have been analysed. Burn wound swabs and biopsies, blood cultures, central venous and urinary catheters, bronchial aspirates, pharyngeal swabs and faecal cultures for a total of 7950 examinations were considered. Staph. aureus was the most frequently isolated bacterium, followed by Staph. epidermidis, Pseud. aeruginosa and E. coli. The antibiograms have shown a low efficacy rate of cephalosporins, even of the latest generation, while with Gram-positive isolates the highest rates of activity were recorded by vancomycin and teicoplanin (100 per cent senstivity). The situation seems better with Gramnegative organisms since they appear to be sensitive to a larger number of antimicrobial agents.

The prompt demonstration without culturing of gram-negative bacteria in burn wound infections

Burn wound sepsis is the most important factor in the morbidity and mortality associated with major burns. Blood cultures often give false negative results and wound biopsy is a much more accurate and reliable means of assessing the burn's microbial status. From 1950 to 1965, due to the introduction of antibiotics, gram-negative organisms became predominant among those recovered from burn wound infections. Although few grampositive organisms are now seen in Gram-stained burn wound biopsies, the light pink or red staining of gram-negative organisms can occasionally go unnoticed (Fig. 1). This is not the case when the biopsy sections are stained with the new positive PATS stain developed in our laboratories for gram-negative bacteria. This reaction deposits silver on the lipopolysaccharides of the outer walls of gram-negative, but not gram-positive, bacteria. The assessment of the microbial content of the specimen site as colonized, infected, or having mixed or unmixed gram-negative microbes is facilitated by this stain (Figs. 2-4).