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Introduction to The Wound Infection Evidence Matrix The development of a structured survey of the evidence for wound infection was one of the principal outputs agreed by the International Wound Infection Institute at its inception. This process began with a simple listing of references (to be found in our “useful documents” section) and will conclude with a comprehensive list of reviewed, surveyed and abstracted papers on wound infection and its treatment. We see the provision of an evidence matrix as the next step along the route. The current version of the matrix is incomplete, but we believe that it is at an appropriate stage to be reviewed by our members. We welcome all of your comments. One of the main features that we wanted to include was a rating system for the evidence. This is always problematic. The literature reveals multiple classifications and evidence hierarchies for ranking evidence 1,2,3,4,5. However, these evidence classifications and hierarchies contain many inconsistencies in interpretation and ranking. Although the gold standard for best evidence is generally considered to be a meta analysis or systematic review of double blinded randomised controlled trials, few, if any, such reviews are to be found in regards to the diagnosis or treatment of wound infection. Our rating system is focussed towards the levels of evidence as follows: 1. Meta analysis and systematic reviews 2. Randomised controlled trials 3. Non randomised controlled trials, case control trials, prospective cohort studies, animal studies, evidence summaries or evidence guidelines 4. Case reports, case series 5. Expert opinion, other literature reviews Highly influential pieces have been published within all the above levels, some of which have contributed to changes in practice. Therefore we are considering the addition of an “impact” rating, separate to the evidence rating, based on the importance or significance of certain papers. We hope that you find this draft of the evidence matrix to be useful. Equally importantly, please give us your opinion on how to improve and add to this document. In particular we would like your feedback on the following: International Wound Infection Institute – Evidence Matrix Page 1 of 53 How useful is the evidence matrix as provided? What other papers should be included? What impact score would you give to significant pieces? Please let us know what you think. All comments will be gratefully received at [email protected] Keryln Carville, Chair, Evidence sub-committee, April 2009 References: 1. Upshur, R. (2003). “Are all evidence-based practices alike? Problems in the ranking of evidence”. CMAJ, 169(7), downloaded http://www.cmaj.ca/cgi/content/full/169/7/672 2. Brown JP, Josse RG; Scientific Advisory Council of the Osteoporosis Society of Canada. 2002 clinical practice guidelines for the diagnosis and management of osteoporosis in Canada. CMAJ 2002;167(Suppl 10):S1-34. 3. Centre for Evidence-Based Medicine. Levels of evidence and grades of recommendation. Oxford: The Centre. Available: www.cebm.net/levels_of_evidence.asp 4. Wright PJ, English PJ, Hungin AP, Marsden SN. Managing acute renal colic across the primary–secondary care interface: a pathway of care based on evidence and consensus. BMJ 2002;325:1408-12. International Wound Infection Institute – Evidence Matrix Page 2 of 53 5. Evans, D. (2003). “Heirarchy of evidence: A framework for ranking evidence evaluating healthcare interventions.” Journal of clinical Nursing. 12(1), 77-84. The Wound Infection Evidence Matrix – April 2009 Author, date Comment Title Key points Grade Wound microbiology and associated approaches to wound management. A thorough review of the literature on wound infection published up until 2001. Key points: all wounds are colonised and progression to infection is as much due to host factors as to the type and number of bacteria present; most open wounds are polymicrobial, with anaerobic bacteria constituting 50% of the species present in infected wounds; swab sampling is easy to carry out but results can be misleading and this should only be carried out if there are clinical signs of infection, if the wound fails to heal or is deteriorating; antibiotics induce bacterial resistance and antiseptics are preferred if topical treatment is required; debridement is an essential part of infection control. In my opinion a literature review as is stated in the conclusion The Calgary biofilm device: new technology for rapid Biofilms have an inherent lack of susceptibility to antibiotics. Ceri et al describe the Calgary Biofilm Device (CBD) which is a method for the rapid and reproducible assay of biofilm susceptibility to antibiotics. Bacteria, biofilms and wound healing (Bowler, Duerden et al. 2001) (Ceri, Olson et al. 1999) Outlines new technology for selecting effective antibiotics in the International Wound Infection Institute – Evidence Matrix The paper describes the formation of biofilms and confirmation of their presence using Page 3 of 53 5 3 Author, date Comment Title Key points Grade treatment of biofilms determination of antibiotic susceptibilities of bacterial biofilms. quantitative microbiology and SEM, followed by the rigorous testing and assessment of the CBD assay using NCCLS reference strains of E coli, P aeruginosa and S aureus. Growth curves demonstrated that biofilms grew uniformly in each of the 96 wells. Antibiotic susceptibility testing demonstrated that, compared to planktonic forms of the same bacteria, 100 to 1000 times the concentration of an antibiotic was required to eradicate the biofilm. The authors claim that the CBD provides a method for the rational selection of antibiotics effective against microbial biofilms. (Costerton, Stewart et al. 1999) A good review of biofilms Bacterial biofilms: a common cause of persistent infections. A good and well-referenced review of biofilms. The review explains how biofilms form and develop, how they differ from planktonic bacteria, the importance of quorum sensing as a possible target for interfering with their development. 5 (Davies, Parsek et al. 1998) The importance of signalling in biofilms is described and it is suggested this could be a way to control biofilms. The involvement of cell-to-cell signals in the development of a bacterial biofilm. This study demonstrates that a cell-to-cell signal (quorum sensing) is required for the differentiation of individual cells of P aeruginosa into complex biofilms. When differentiation is hindered by a mutation, the biofilm becomes abnormal and is sensitive to a detergent biocide (SDS). Without the signalling device, the biofilms were not able to grow with the proper architecture and did not leave sufficient space between colonies. 3 International Wound Infection Institute – Evidence Matrix The authors suggest that inhibition of the quorum sensing signals could be possible ways to control biofilms, given their resistance to most antibiotics. Page 4 of 53 Author, date Comment Title Key points Grade (Dow, Browne et al. 1999) Review Infection in chronic wounds: controversies in diagnosis and treatment. A thorough review that includes: definitions of contamination, colonization and infection; the pathogenesis of wound infection and how the inflammatory response can delay wound healing; diagnosis of wound infection; quantification of bacterial burden. 5 Regarding bacterial burden, the authors caution that there is no hard cut-off figure above which colonization turns to infection and that the level of microbial burden alone can not be used to define infection. They stress the importance of bacterial species and variety, and the capacity of the host to tackle infection. They warn of the difficulties of quantitative biopsy and argue the case for semi-quantitative assessment. The paper also provides a detailed critique of specimen collection and culture techniques and concludes with a thorough overview of treatment options including mechanical (debridement), antiseptics and the role of antibiotics. A useful table summarises the antimicrobial options for empiric therapy. A small number of the concepts have been challenged over the years since the publication of this review, but on the whole it is a thorough and valuable resource on the subject of wound infection. (Dowd, Sun et al. 2008) Highly significant study Survey of bacterial diversity in chronic wounds using Pyrosequencing, DGGE and full International Wound Infection Institute – Evidence Matrix This study used specific techniques to identify the major populations of bacteria that occur in the biofilms found in three types of chronic wound: diabetic foot ulcer, venous leg ulcer and pressure ulcer. The techniques were: three separate I 6S-based molecular amplifications, followed by pyrosequencing, shotgun Sanger sequencing and denaturing gradient gel electrophoresis. All chronic wound types contained certain specific major populations of bacteria: Page 5 of 53 3 Author, date Comment Title Key points Grade ribosome shotgun sequencing. Staphylococcus, Pseudomonas, Peptoniphilus, Enterbacter, Stenotrophomonas, Finegoldia and Serratia species. However, each of the wound types showed marked differences in their bacterial populations. For example, in venous ulcers over 80% of the bacteria were facultative anaerobes, compared with 62% in diabetic foot ulcers, and just over 20% in pressure ulcers. Pressure ulcers on the other hand comprised over 60% of strict anaerobes, compared with nearly 30% in diabetic foot ulcers and virtually none in venous ulcers. Different wound types also showed a different level of oxygen tolerance amongst their bacterial populations. The authors suggest that this may imply each wound type has a distinct pathophysiology that affects the ecology of the wound environment determiging which bacteria can develop. Results were compared with those from traditional culture-based analyses. In only one wound type did the culture methods correctly identify the primary bacterial population. Standard culturing techniques are inherently flawed as they only examine the 1% of microorganisms that are able to grow rapidly in pure culture. Also, certain populations may never be cultured in the laboratory due to reduced metabolic activity, obligate cooperation with other bacteria, need for specialized nutrients or environmental conditions. The paper gives full details of the bacteria identified. (Hill, Davies et al. 2003) Molecular analysis reveals a much greater diversity of Molecular analysis of the microflora in International Wound Infection Institute – Evidence Matrix Culture analyses of CVLU generally reveal staphylococci, streptococci, enterococci and facultative Gram-negative bacilli. However, anaerobic isolation techniques and prolonged incubation reveal the presence of fastidious and slow-growing anaerobic species such as Page 6 of 53 3 Author, date Comment Title Key points Grade microflora in chronic wounds than do culture techniques. chronic venous leg ulceration. Fusobacterium and peptostreptococci. Cultivation-dependent methods for characterising the microflora of chronic wounds are limited. The authors describe the analysis using 16S rDNA sequences of tissue from a CVLU which demonstrated significantly greater bacterial diversity than culture methods. Sequences even suggested novel species of bacteria. This technique can clearly not be used routinely so the clinical application is limited but may inform treatment in deteriorating or longlasting wounds. The study states that this was one patient and one wound that was analysed? Would that make it a 4? (James, Swogger et al. 2008) Well-designed and highly significant study revealing that biofilms may be present in at least 60% of chronic nonhealing wounds Biofilms in Chronic wound specimens were taken from 77 subjects and acute wound specimens from chronic wounds. 16. All specimens were cultured using standard techniques and in addition, light and scanning electron microscopy were used to analyse 50 chronic and 17 acute specimens. Molecular analyses were performed on the other 27 chronic specimens. There was a statistically significant difference between the chronic and acute specimens in terms of presence of biofilm: 60% of the chronic but only 6% of the acute (p<0.001). Molecular analysis showed that there were polymicrobial communities and bacteria, including strictly anaerobic, that were not revealed by culture. The study shows that biofilms are not necessarily capable of detection using standard clinical techniques. International Wound Infection Institute – Evidence Matrix Page 7 of 53 3 Author, date Comment Title Key points Grade (Laato, Niinikoski et al. 1998) This paper suggests a mechanism to explain why S aureus sometimes appears to accelerate wound healing. Inflammatory reaction and blood flow in experimental wounds inoculated with Staphylococcus aureus This paper is often quoted as it demonstrated that certain low levels of bacteria in a wound could actually enhance healing, through stimulating inflammation which in turn would enhance local blood flow. 3 P aeruginosa can enlarge ulcers and delay healing. S aureus and haemolytic strep also delay healing Bacterial colonisation and healing of venous leg ulcers. Fifty-nine patients with VLUs were followed with frequent semi-quantitative culture of bacteria from the ulcer surface for 180 days. The ulcer area was also measured. At 90 and 180 days the authors found that ulcers colonised with P aeruginosa were significantly larger than those without; and significantly fewer of them healed completely during the observation period. Suggested that 105 bacteria per gram of tissue was a critical level for infection. The effect of microbial contamination on musculocutaneo (Madsen, Westh et al. 1996) (Murphy, Robson et al. 1986) In an animal experiment, wounds were created and sponge implants were used as a matrix to encourage growth of granulation tissue. The implants were injected either with saline (control), or S aureus at concentrations of 102 or 105 microorganisms/ml. Implants inoculated with 105 organisms developed infection with pus formation, while implants inoculated with 102 showed no signs of infection but had an enhanced local blood flow. 3 Ulcers with S aureus or haemolytic streptococci healed significantly more slowly than those without. International Wound Infection Institute – Evidence Matrix Granulating wounds were inoculated with varying levels of bacteria per gram of tissue: 10 4, 105 or 106 and were then covered with musculocutaneous or random flaps or left uncovered. Bacterial proliferation was evident in all the heavily contaminated wounds (106) while in the minimally contaminated wounds (104) both types of flap achieved wound healing and decreased the bacterial level in the wound. In the intermediate group (105) Page 8 of 53 3 Author, date Comment Title Key points Grade us and random flaps. musculocutaneous flaps lowered the bacterial count and allowed wound closure, whereas random flaps failed. This study is relevant to clinicians beyond the field of surgery as it established that the 10 5 level of bacteria was an important tipping point in the development of infection – all other things being equal. Significant impact (Ovington 2003) Low evidence but useful piece Bacterial toxins and wound healing. An educational piece that describes critical colonisation as a stage of colonisation that occurs before invasive infection. The current view is that critical colonisation is actually the presence of biofilm. The rest of the paper deals with bacterial toxins, describing the nature and effects of exoand endo-toxins. While many educational pieces describe the effects of bacteria in wounds, this is one of the very few that deals specifically with the actions of bacterial toxins. The author explains that while antimicrobials may reduce the amount of exotoxin produced by bacteria, they have no effect on exotoxin that is already in the wound. Also, when Gramnegative bacteria are destroyed, they release endotoxins from their cell wall, so topical antimicrobials may contribute temporarily to an increase in endotoxin levels. The author advocates the use of absorbent dressings and activated charcoal to remove toxins from the wound bed and describes a silver dressing that is based on an activated charcoal cloth (Actisorb). International Wound Infection Institute – Evidence Matrix Page 9 of 53 5 Author, date Comment Title Key points Grade (Robson and Heggers 1970) An influential paper that established 105 bacteria per gram of tissue as a cut-off level for uncomplicated healing of wounds. Delayed wound closures based on bacterial counts. At the time of publication of this paper, there was much debate about the effect of bacterial burden on the healing process and whether it was possible to predict successful wound closure based on the bacterial count. The aim was to find a method of predicting success that would therefore allow delayed closure of contaminated non-traumatic wounds. In 1969 Heggers developed a rapid smear method for bacterial quantification and in this study, Robson aimed to use the technique prospectively in a series of wounds to see if bacterial burden, as identified by the swab method, could predict wound closure. 3 Ninety-five cases were studied in which closure had been delayed through, for example, removal of sutures or drainage of surgical abscess. During the period of delay, the wound was inspected and cleaned daily, and debrided if necessary. Quantitative and qualitative cultures were performed at the time of surgery and at attempted closure. An aseptic tissue sample is prepared and examined under a microscope. The authors claim that the process takes no more than one hour. Once a wound had 105 or fewer bacteria per gram, delayed closure was performed. The only exceptions were wounds involving β-haemolytic streptococci. Eighty-nine incisions closed when the bacterial count was less than 10 5 and progressed to rapid healing. Only one of the four cases containing more than this level was successful. The authors suggest that this bacterial level can be used to predict closure with 96% accuracy. The paper “Predicting skin graft survival” deals with the same concept. (Robson and Krizek 1973) International Wound Infection Institute – Evidence Matrix Page 10 of 53 Author, date Comment Title Key points Grade (Robson 1997) Interesting but not highly practical. Wound infection: a failure of healing caused by an imbalance of bacteria. A summary of the state of knowledge at the time about the healing process in surgical, acute and chronic wounds. 5 Qualitative bacteriology and leg ulcer healing. The bacterial profile of leg ulcers in 52 patients were investigated to identify whether specific bacterial groups delay healing, whether the bacterial flora changes as ulcers heal, and whether the changes influence healing. (Trengove, Stacey et al. 1996) Study that established the number of bacterial species was more important than the type in delaying healing. Unlike other reviews, such as those by Dow, this is not highly practical, but does contain some interesting background in a number of areas that are not always included in other reviews. In particular, the review collects together and summarises earlier work by Robson and others in the field of surgical research into bacterial burden. 3 The authors found that delay in healing did not appear to be associated with any specific bacterial group; rather, it was the number of types of bacteria that was most strongly associated with delayed healing. The presence of four or more bacterial groups was statistically significantly associated with delayed healing. There was no apparent connection between the change in flora and wound healing. Significant impact (Wheat, Allen et al. 1986) Outlines the importance of a “reliable” wound swab technique Diabetic foot infections: bacteriologic analysis. International Wound Infection Institute – Evidence Matrix Diabetic foot infections were evaluated by taking 54 specimens of tissue and avoiding contamination with foot ulcer. A further 94 “unreliable” specimens were also taken. In the reliable specimens, the most common isolates were staph species, enterococcus species, corynebacterium species and various enterobacteriaecae. Anaerobic isolates included Page 11 of 53 3 Author, date Comment Title Key points Grade Peptostreptococcus magnus and prevotii, and bacteroides species. The results of cultures on the unreliable specimens were similar. When “reliable” and “unreliable” specimens were taken simultaneously from 26 patients, the results agreed in only seven patients, however, the antibiotics that would have been selected in 24 cases would have adequately covered all the pathogens whichever specimen was used. The authors conclude that diabetic foot infections usually contain mixed bacterial flora and that uncontaminated specimens are to be preferred. Diagnosis of infection (Bowler 2003) Contribution to the debate on the significance of the 105 figure as a determinant of critical colonisation The 105 bacterial growth guideline: reassessing its clinical relevance in wound healing. International Wound Infection Institute – Evidence Matrix The microbiology of wounds is a key determinant in healing and clinicians generally accept that a level of microbial (ie, bacterial) growth greater than 100,000 viable organisms per gram of tissue can be used to diagnose infection. Although other factors that predispose a wound to infection are widely recognized, today's wound care practitioners are influenced primarily by the 105 guideline, with treatment being based on the microbial count in deep or superficial tissue. However, to appropriately manage microbially challenged wounds (eg, heavily colonized and clinically infected), a more balanced awareness of the broader issues relating to micro-organisms and wounds is needed. The types of micro-organisms, their interactions with each other and with the wound environment, the local conditions, and host resistance are all key factors that collectively influence healing. From a microbiological perspective, successful wound healing is dependent on maintaining a host-manageable bioburden. If local conditions favor microbial growth, a wound may fail to heal and become infected, requiring topical antiseptics or antibiotics to supplement the host inflammatory response and restore balance in favor of the host. This paper provides a critical examination Page 12 of 53 5 Author, date Comment Title Key points Grade of the 105 guideline to enhance clinician understanding and utilization of a commonly applied diagnostic consideration. (Ceri, Olson et al. 1999) (Cutting and Harding 1994) A method is described for the rapid assessment of biofilm susceptibility A useful and influential paper that had a widespread effect on clinical practice The Calgary biofilm device: new technology for rapid determination of antibiotic susceptibilities of bacterial biofilms. Biofilms have an inherent lack of susceptibility to antibiotics. Ceri et al describe the Calgary Biofilm Device (CBD) which is a method for the rapid and reproducible assay of biofilm susceptibility to antibiotics. Criteria for identifying wound infection. Useful source of background information from various audits about wound infection rates and the cost to healthcare systems of managing infections. The paper describes the formation of biofilms and confirmation of their presence using quantitative microbiology and SEM, followed by the rigorous testing and assessment of the CBD assay using NCCLS reference strains of E coli, P aeruginosa and S aureus. Growth curves demonstrated that biofilms grew uniformly in each of the 96 wells. Antibiotic susceptibility testing demonstrated that, compared to planktonic forms of the same bacteria, 100 to 1000 times the concentration of an antibiotic was required to eradicate the biofilm structure. The authors claim that the CBD provides a method for the rational selection of antibiotics effective against microbial biofilms. However, the authors note that traditional criteria for identifying wounds, such as the presence of pus or inflammation may not be adequate in some circumstances. They support this by citing figures showing high percentages of infection becoming evident in patients only after they had been discharged. The authors provide a list of criteria for identifying wound infection. This includes the International Wound Infection Institute – Evidence Matrix 3 Page 13 of 53 3 Author, date Comment Title Key points Grade traditional criteria (abscess, cellulitis, discharge) but also some additional criteria that should alert a clinician to the possibility of infection (delayed healing, discolouration, friable granulation tissue, unexpected pain or tenderness, pocketing or bridging at the wound base, abnormal smell and wound breakdown). Some of these criteria were suggested on the basis of other studies, and some were based on empirical data from a large, multidisciplinary practice (clinical experience). (Cutting 1998) Inter-rater reliability testing of clinical wound infection and validity testing of pre-determined criteria The identification of infection in granulating wounds by registered nurses. The author carried out a study to validate the criteria for wound infection he had proposed in an earlier paper (1994). Twenty ward nurses were asked to view wounds and make a decision on the infection status using their own criteria. A researcher also viewed the wounds using the 1994 Cutting and Harding criteria and a microbial assay was also taken via wound swab. A total of 40 different patients were viewed and the findings suggested that the 1994 criteria had a high degree of validity. All but one of the decisions made by the researcher were corroborated by the wound swab culture. (Cutting and White 2005) Extremely valuable resource, often used in other studies Criteria for identifying wound infection - revisited. A 1994 paper by Cutting and Harding proposed a set of criteria which could be used to 5 identify wound infection. These were based on observations made in a large clinical practice and were subsequently validated by Cutting (1998) and Gardner (2001). The authors acknowledge that a weakness of the original criteria is that they do not differentiate between wounds of different types which might make them less applicable in some cases. Using a review of the literature, Cutting and White have generated a list of infection criteria that are applicable to various types of wound: acute, surgical, diabetic foot ulcer, venous and arterial leg ulcer, pressure ulcer and burn. The paper includes a table listing the criteria International Wound Infection Institute – Evidence Matrix Page 14 of 53 3 Author, date Comment Title Key points Grade for each of these wound types. Cutting KF, White RJ, Mahoney P, Harding KG. Reinforces and validates the Cutting & White 2005 criteria for wound infection. This article appears in the EWMA Position Document. Identifying criteria for wound infection. London: MEP (Dowd, Sun et al. 2008) Very important study revealing the short-comings of traditional culture techniques in identifying biofilms. Clinical identification of wound infection: a Delphi approach. A multidisciplinary Delphi group of 54 expert members was used to generate and rank infection criteria for acute wounds, arterial and venous leg ulcers, burns, diabetic foot ulcers and pressure ulcers. Cellulitis, malodour, pain, delayed healing or deterioration of the wound and/or wound breakdown were determined to be the common criteria for infection amongst all six wound types. 5 This study used specific techniques to identify the major populations of bacteria that occur in the biofilms found in three types of chronic wound: diabetic foot ulcer, venous leg ulcer and pressure ulcer. The techniques were: three separate I 6S-based molecular amplifications, followed by pyrosequencing, shotgun Sanger sequencing and denaturing gradient gel electrophoresis. 3 In: EWMA Position Document. Identifying criteria for wound infection. London: MEP Ltd, 2005. Survey of bacterial diversity in chronic wounds using Pyrosequencing, DGGE and full ribosome International Wound Infection Institute – Evidence Matrix All chronic wound types contained certain specific major populations of bacteria: Staphylococcus, Pseudomonas, Peptoniphilus, Enterbacter, Stenotrophomonas, Finegoldia Page 15 of 53 Author, date Comment Title Key points Grade shotgun sequencing. and Serratia species. However, each of the wound types showed marked differences in their bacterial populations. For example, in venous ulcers over 80% of the bacteria were facultative anaerobes, compared with 62% in diabetic foot ulcers, and just over 20% in pressure ulcers. Pressure ulcers on the other hand comprised over 60% of strict anaerobes, compared with nearly 30% in diabetic foot ulcers and virtually none in venous ulcers. Different wound types also showed a different level of oxygen tolerance amongst their bacterial populations. The authors suggest that this may imply each wound type has a distinct pathophysiology that affects the ecology of the wound environment determiging which bacteria can develop. Results were compared with those from traditional culture-based analyses. In only one wound type did the culture methods correctly identify the primary bacterial population. Standard culturing techniques are inherently flawed as they only examine the 1% of microorganisms that are able to grow rapidly in pure culture. Also, certain populations may never be cultured in the laboratory due to reduced metabolic activity, obligate cooperation with other bacteria, need for specialized nutrients or environmental conditions. The paper gives full details of the bacteria identified. (Gardner, Frantz et al. 2001) A useful and frequently cited article. The validity of the clinical signs and symptoms used to identify International Wound Infection Institute – Evidence Matrix Following on from the publication in 1994 of suggested criteria for wound infection (Cutting and Harding 1994) Gardner et al carried out a study to validate these suggested criteria. Thirty-six chronic wounds were assessed for the 12 signs and symptoms of infection. Five Page 16 of 53 3 Author, date Comment Title Key points Grade localized chronic nurses were trained in identifying the criteria. wound The wounds were then quantitatively cultured via biopsy to identify correlation between infection. the assessment and infection. The presence or absence of signs and symptoms was compared with the infection status as defined by the culture results. The authors found that although each sign and symptoms was valid to some degree, four items: increasing pain, friable granulation tissue, foul odour and wound breakdown were valid criteria based on four parameters – sensitivity, specificity, discriminatory power and positive predictive value. They also suggest that in chronic wounds the signs specific to secondary wounds (as proposed by cutting and Harding) were better indicators of chronic wound infection than the classic signs. The authors also found that inter-observer reliability ranged from 0.53 to 1.00 suggesting that the check-list could be used reliably by a variety of people. Inter-clinician variability was not assessed and the authors did not attempt to discriminate by wound type but nonetheless the results were sufficiently robust to warrant inclusion in routine wound assessment. (Hill, Davies et al. 2003) Molecular analysis of the microflora in chronic venous leg ulceration. International Wound Infection Institute – Evidence Matrix Culture analyses of CVLU generally reveal staphylococci, streptococci, enterococci and facultative Gram-negative bacilli. However, anaerobic isolation techniques and prolonged incubation reveal the presence of fastidious and slow-growing anaerobic species such as Fusobacterium and peptostreptococci. Cultivation-dependent methods for characterising Page 17 of 53 3 Author, date Comment Title Key points Grade the microflora of chronic wounds are limited. The authors describe the analysis using 16S rDNA sequences of tissue from a CVLU which demonstrated significantly greater bacterial diversity than culture methods. Sequences even suggested novel species of bacteria. This technique can clearly not be used routinely so the clinical application is limited but may inform treatment in deteriorating or longlasting wounds. Topical treatments: antiseptics and antibiotics (Cooper, Laxer et al. 1991) (Drosou, Falabella An important review et al. 2003) which collected together and explained the The cytotoxic effects of commonly used topical antimicrobial agents on human fibroblasts and keratinocytes. An in vitro study which assessed the effect of a number of topical antimicrobials on human dermal fibroblasts and epidermal keratinocytes. The agents studied were: polysporin, bacitracin, polymyxin B, GU irrigant, neomycin, gentamicin, sulfamylon, betadine, acetic acid and modified Dakins solution. The authors conclude that many antimicrobial agents have adverse effects on fibroblasts and keratinocytes. However, subsequent animal and human studies found that the in vivo situation was different (see Drosou). Antiseptics on A significant review article which attempted to resolve the controversy about the use of wounds: an area antiseptics on open wounds. Some authors had argued against their use, citing cytotoxicity of controversy. data in support; other investigators found no evidence of adverse effects on healing. International Wound Infection Institute – Evidence Matrix 3 Page 18 of 53 5 Author, date Comment Title various animal and human studies into antiseptics. This paper helped to dispel the view that antiseptics were cytotoxic in vivo. Key points Grade The review begins with a useful section on antiseptics, and their use on intact skin, before providing a rationale for their use in wounds, which includes their ability to kill many different types of bacteria and the very low possibility that bacteria will develop resistance against them. Balancing this, the authors summarise the arguments against using antiseptics in open wounds. This includes the possible cytotoxicity demonstrated by in vitro studies, and the possibility that antiseptics will be largely inactivated by wound fluids. The article then reviews the animal and human studies of antiseptics and ignores the in vitro studies, on the basis that the laboratory studies can not take into account the physiological effects pertaining to actual wounds. The article reviews povidone-iodine, cadexomer iodine, hydrogen peroxide, acetic acid, chlorhexidine and silver. Povidone-iodine. Animal studies found little benefit but only used a single application or applications more than three hours after wounding. Most human trials proved the efficacy of povidone-iodine in burns, sutured lacerations, non-infected venous leg ulcers, surgical wounds (1%, not 5%). Other studies could not confirm these results. The reported effects on wound healing are conflicting which may be due to differences in the parameters evaluated, the assessment times, the concentrations, the diversity of wounds and, in animal experiments, the type of animal. Most clinical studies showed no adverse effects on the wound healing rate when a 1% solution is used. Cadexomer iodine. Positive results have been found both in animal and human studies (see section on Iodine for details). Animal studies suggest that cadexomer iodine increased epidermal regeneration and epithelialisation but has no effect on granulation tissue formation, neovascularisation or wound contraction. In clinical studies cadexomer iodine International Wound Infection Institute – Evidence Matrix Page 19 of 53 Author, date Comment Title Key points Grade has not been found to have any detrimental effects on wound healing, and may even have beneficial effects. Hydrogen peroxide. The situation with hydrogen peroxide is less clear-cut with some conflicting results. Overall it appears that it does not negatively affect wound healing, but is not very effective. The effervescent effect may provide some mechanical benefit in loosening debris. Acetic acid. In vivo studies did not confirm the cytotoxic effects found in in vitro studies. Chlorhexidine. Chlorhexidine appears to be relatively safe with little effect on wound healing but there are insufficient results to draw conclusions about its utility in open wounds. Silver. Silver compounds do not have a negative effect on wounds and may accelerate wound healing. See the section on silver compounds as many papers in this area have been published since the Drosou paper. The paper contains very comprehensive tables listing all the studies reviewed. (Fumal, Braham et al. 2002) The beneficial toxicity paradox of antimicrobials in leg ulcer healing impaired by a International Wound Infection Institute – Evidence Matrix Two lesions in each of 51 patients with chronic leg ulcers were studied. The ulcers were long-standing but were not apparently infected. The two target ulcers were randomised to receive saline rinse and hydrocolloid (control) or control plus antimicrobial. The test antimicrobials were: 10% povidone-iodine, 1% silver sulfadiazine (SSD) or 5% chlorhexidine. After six weeks, the healing rate was slightly improved with SSD and chlorhexidine, but was Page 20 of 53 2 Author, date Comment Title Key points Grade polymicrobial significantly improved with povidone-iodine (p<0.01). flora: a proof-ofBased on histological analysis, the authors suggest that the beneficial effect of povidoneconcept study. iodine is not due just to an antimicrobial effect but to a positive effect on biological mechanisms. (Gruber, Vistnes et al. 1975) Very influential study which refuted the suggestion that antiseptics are detrimental to healing The effect of commonly used antiseptics on wound healing. An animal and clinical study to evaluate the effect of some common antiseptic agents on wound contraction, epithelialisation, and migration of epidermis across the wound surface. Three agents were studied: acetic acid (25%), povidone-iodine (Betadine), hydrogen peroxide (3%) and saline control. The agents were applied to partial and full-thickness wounds in 60 rats, or to donor sites in 40 patients until full epithelialisation had taken place. Serial microscopy was used to study the effect of the agents. 3 No delay of epithelialisation compared to saline control was noted either macroscopically or microscopically with any of the agents. In fact, hydrogen peroxide shorted the healing time (defined as a pink surface, without scab). The authors suggest this may be due to the effervescent action of hydrogen peroxide allowing earlier separation of the scab. This may also be responsible for some bullae which developed on the donor site. (Kucan, Robson et al. 1981) Comparison of silver sulfadiazine, povidone-iodine and physiologic saline in the treatment of International Wound Infection Institute – Evidence Matrix 2/3 The presence of bacteria and local infection is an important factor in the local management of chronic pressure ulcers. For successful closure of the ulcer, the bacterial count should be 105 or less per gram of tissue in the granulating wound. In a prospective randomized study of 45 (eventually 40) hospitalized patients, silver sulfadiazine (Silvadene) cream and Page 21 of 53 Author, date Comment Title Key points Grade chronic pressure ulcers. povidone-iodine (Betadine) solution were compared to physiologic saline for effectiveness in preparing pressure ulcers for closure. Quantitative bacteriologic techniques on tissue biopsy specimens were used for objective evaluation. In 100 percent of the ulcers treated with silver sulfadiazine cream (15 patients) the bacterial counts were reduced to 10(5) or less per gram of tissue within the three-week test period, compared to 78.6 percent in those treated with saline (14 patients) and 63.6 percent in those treated with povidoneiodine solution (11 patients). Moreover, the ulcers treated with silver sulfadiazine cream responded more rapidly, with one-third showing bacterial levels of less than 10(5) within three days, and half within a week (Published abstract). (Lineweaver, Howard et al. 1985) A paper that has often been cited as proof that antiseptic agents adversely affect wound healing. Later studies, using sustained release preparations, suggested otherwise. Topical antimicrobial toxicity. International Wound Infection Institute – Evidence Matrix Three topical antibiotics and four antiseptics were applied to cultured human fibroblasts to 3 quantitatively assess their cytotoxicity. The antibiotics used were bacitracin, 1% neomycin sulphate and 2% kanamycin sulphate; while the antiseptics were 1% povidone-iodine, 0.25% acetic acid, 0.5% sodium hypochlorite and 3% hydrogen peroxide. At full strength, none of the antibiotics was toxic to fibroblasts. The four antiseptics were found to be cytotoxic [at these concentrations]. Serial dilutions showed that the cytotoxic effects of hydrogen peroxide and acetic acid exceeded their bacterial effects, whereas it was possible to prepare dilutions of non-cytotoxic povidone-iodine and sodium hypochlorite. The antiseptic agents and saline control were also applied to animal wounds three times a day, and the size of the unepithelialised area of the wounds was recorded at 4, 8, 12 and 16 Page 22 of 53 Author, date Comment Title Key points Grade days after wounding. At four days, wounds irrigated with 1% povidone-iodine were significantly weaker than wounds irrigated with saline, other topical agents, or unirrigated wounds. Wound epithelialisation was significantly retarded at four days by povidone-iodine and acetic acid, at eight days by povidone-iodine, acetic acid and sodium hypochlorite and at 16 days by sodium hypochlorite. (Mertz, Alvarez et al. 1984) (Viljanto 1980) Fairly useful study which showed that one single application of an antiseptic agent has limited antibacterial effect. Useful A new in vivo model for the evaluation of topical antiseptics on superficial wounds: the effect of 70% alcohol and povidone-iodine solution. Six partial thickness wounds in each of nine pigs were inoculated with S aureus and were then treated with 0.1ml of either 70% alcohol, 10% povidone-iodine solution or distilled water control. The agents were rubbed into the wound for 30 seconds. The agents were left on the wounds for one minute, three minutes or 24 hours and were cultured for bacteria. Disinfection of surgical wounds without inhibition of normal wound healing. While intact skin can withstand very strong disinfective agents, the cells of a fresh surgical wound are much more susceptible to damage. International Wound Infection Institute – Evidence Matrix 3 After one minute, neither solution reduced the number of pathogens. After three minutes, both agents produced a slight reduction, and after 24 hours, povidone-iodine slightly reduced the number of pathogens. After 24 hours, neither agent reduced the number of pathogens below 105 CFU per ml. The authors conclude that single applications of these agents only provide limited efficacy against pathogens in superficial wounds. This treatment design was chosen as it mimics the usual emergency treatment of abrasions. Povidone-iodine solutions (5% and 1%) or no disinfectant were applied to the surgical wounds of 294 paediatric patients, 283 of whom had undergone appendectomy. The disinfectant was applied to the wound by a nurse without the surgeon knowing which Page 23 of 53 3 Author, date Comment Title Key points Grade patient would be treated. Regardless of the state of the appendix there was a significant increase in wound infections in the 5% group compared to the control (p<0.001). Using a cellstic method, it was found that the 5% solution inhibited leukocyte migration. Most of the nuclei were pyknotic and the chromatin often appeared to lack structure. No cell aggregates or fibroblasts were seen. The 1% solution allowed better cellular movement and attachment, and some cell aggregates were visible. Cell morphology was very similar to that in the saline control. No wound infections developed in the patients disinfected with 1% solution; 8.5% of patients in the saline control developed infections. Although 1% povidone-iodine is useful in local disinfection of the wound, where infection progressed beyond the appendix, such as in peritonitis, local disinfection was inadequate. Iodine (Apelqvist and Ragnarson 1996) Cavity foot ulcers in diabetic patients: a comparative study of cadexomer iodine ointment and standard treatment. An 41 patients with deep exudative diabetic foot ulcers were included in a 12 week, open, randomized, comparative study comparing cadexomer iodine treatment with standard treatment. International Wound Infection Institute – Evidence Matrix Page 24 of 53 No clinical difference between Iodosorb and other treatments: gentamicin solution, stretodornase/streptokinase, dry saline gauze. 2 Author, date Comment Title Key points Grade economic analysis alongside a clinical trial. (Danielsen, Cherry et al. 1997) (Hansson 1998) Large study, but the section on infection is weak as little detail is given. Cadexomer iodine in ulcers colonised by Pseudomonas aeruginosa. An open, uncontrolled, multi-centre pilot study in three countries (Sweden, Denmark, UK) in 3 19 patients with venous leg ulcer. The effects of cadexomer iodine paste in the treatment of venous leg ulcers compared with hydrocolloid dressing and paraffin gauze dressing. Cadexomer Iodine Study Group. A 12 week randomized, open, controlled, multicenter study with 153 patients with exudating venous leg ulcers who were treated with cadexomer iodine paste, hydrocolloid dressing, or paraffin gauze dressing, combined with short-stretch compression bandages. International Wound Infection Institute – Evidence Matrix Bacterial cultures for growth of Ps aeruginosa were carried out regularly. After one week of treatment, 11/17 ulcers had negative culture for Ps aeruginosa, and 6/8 at 12 weeks. The authors report that wound infection was more common with hydrocolloid and paraffin gauze than with the cadexomer iodine paste but give no detail as to how infection was assessed or recorded. At weeks 4 and 8, wounds treated with cadexomer iodine had significantly lower levels of slough than those treated with paraffin gauze, but there was no significant difference between cadexomer iodine and hydrocolloid. Page 25 of 53 2 Author, date (Hillström 1988) (Holloway, Johansen et al. 1989) Comment Title Key points Grade Iodosorb compared to standard treatment in chronic venous leg ulcers - a multicenter study. Multi-centre study with 93 patients. 3 Multicenter trial of cadexomer iodine to treat venous stasis ulcer. Controlled, cross-over study in the US with 75 patients assigned to cadexomer iodine or standard treatment (saline, wet-to-dry compression) for venous stasis ulcers. The number of isolates of S aureus was significantly lower after application of cadexomer iodine. Ps aeruginosa and other organisms were also significantly reduced. Cleansing action was assessed visually on scales that assessed the amount of exudate, pus and debris on the ulcer surface. Cadexomer iodine appeared to be more effective but not to the level of statistical significance. Nothing is specifically mentioned about antimicrobial action but slough removal was more effective with cadexomer iodine. International Wound Infection Institute – Evidence Matrix Page 26 of 53 3 Author, date Comment Title Key points Grade (Mertz, Davis et al. 1994) Well-conducted study but small numbers Can antimicrobials be effective without impairing wound healing? The evaluation of cadexomer iodine ointment. An animal study in which partial thickness wounds infected with S aureus or Ps aeruginosa were treated with cadexomer iodine ointment, ointment base or no treatment. 2 At 24, 48 and 72 hours there were significantly fewer numbers of S aureus recovered from cadexomer-iodine treated wounds compared to the other two groups (p<0.03). In wounds inoculated with Ps aeruginosa, the number of microbes recovered from all wounds fell markedly between 24 and 72 hours. Only at 48 hours did cadexomer iodine ointment reduce bacterial levels compared to no treatment, but not to the ointment base. There was a sustained effect against S aureus, but the low numbers of Ps aeruginosa seen in all wounds suggests that no treatment group provided ideal conditions for its growth. In addition to the antimicrobial action demonstrated in this study the authors showed that there no trade-off with healing. They found that cadexomer iodine had no deleterious effect on epithelialisation, indeed it accelerated healing compared to air-exposed wounds. (Mertz, OliveiraGandia et al. 1999) The evaluation of a cadexomer iodine wound dressing on methicillin resistant Staphylococcus aureus (MRSA) in acute International Wound Infection Institute – Evidence Matrix An animal study in which partial thickness wounds were infected with MRSA and were treated with either cadexomer iodine or the vehicle dressing without iodine, or with no treatment. The cadexomer iodine dressing significantly reduced MRSA and total bacteria compared to wounds with either no treatment or the inactive dressing. Page 27 of 53 3 Author, date Comment Title Key points Grade Controlled trial of Iodosorb in chronic venous ulcers. Randomised, optional cross-over trial of 61 out-patients with venous ulcers using cadexomer iodine or standard dressings. 3 Bactericidal activity and toxicity of iodinecontaining solutions in wounds. Complexing iodine with povidone (polyvinylpyrrolidone) or surfactants significantly limits the quantity of free iodine. Reduction of the free iodine level eliminates the adverse properties of staining, instability, and irritation and also alters bactericidal activity. Addition of detergents to create surgical scrub solutions further reduces the activity of iodine. In vitro testing indicated that the bactericidal activity of iodophors was inferior to that of uncomplexed aqueous iodine. In vivo tests proved that aqueous iodine significantly potentiated the development of infection. Although the povidone iodophor did not enhance the rate of wound or infection, it offered no therapeutic benefit when compared with control wounds treated with saline solution. Addition of detergents to the povidone iodophor was deleterious, with the wounds exposed to this combination displaying significantly higher infection rates than untreated control wounds. Based on these results, aqueous iodine solutions and iodophor surgical scrub solutions should not be used on broken skin. Aqueous iodophors can be used in wounds, but no therapeutic benefit from such use was found in this study (Published abstract). wounds. (Ormiston, Seymour et al. 1985) (Rodeheaver, Bellamy et al. 1982) Good trial International Wound Infection Institute – Evidence Matrix No significant effect on bacterial colonisation. A wide and changing variety of organisms were cultured, and there was no consistent trend towards eradication of particular pathogens, irrespective of the treatment or response of the ulcer. Page 28 of 53 3 Author, date Comment Title Key points Grade (Skog, Arnesjö et al. 1983) Well-conducted A randomized trial comparing cadexomer iodine and standard treatment in the out-patient management of chronic venous ulcers. A randomized trial in 93 out-patients comparing cadexomer iodine and standard treatment in the treatment of chronic venous leg ulcers. 2 In-patient treatment of chronic varicose venous ulcers. A randomized trial of cadexomer iodine versus standard dressings. 2 A total of 67 patients with treatment resistant chronic venous ulcers were admitted to hospital for 6 weeks of bed rest and daily dressings. The patients came from a rural area in Poland with poor socioeconomic conditions. They were randomized to treatment with either standard dressings or with cadexomer iodine. After 6 weeks all but four patients had shown a clear reduction of ulcer area; the mean reduction was 54% within the former group and 71% with cadexomer iodine. The latter treatment was significantly more effective than the standard hospital dressings in debriding the ulcer, accelerating healing and reducing pain. Elevation of serum concentrations of protein-bound iodine occurred after treatment with cadexomer iodine in patients with large ulcers, but tests of thyroid function showed no changes associated with the use of cadexomer iodine. (Laudanska and Gustavson 1988) Cleansing effect of cadexomer iodine was significantly greater than that of standard treatment (p<0.005). Cadexomer iodine significantly reduced infection with S aureus, Ps aeruginosa, and other organisms such as: Streptococcus, Proteus, Enterobacteria and Klebsiella. It is concluded that cadexomer iodine significantly accelerates the healing of chronic, infected, treatment-resistant, venous ulcers in hospitalized patients. International Wound Infection Institute – Evidence Matrix Page 29 of 53 Author, date Comment Title Key points Grade Chlorhexidine (Drosou, Falabella et al. 2003) Antiseptics on A significant review article which attempted to resolve the controversy about the use of wounds: an area antiseptics on open wounds. of controversy. They found that chlorhexidine appears to be relatively safe with little effect on wound healing but there are insufficient results to draw conclusions about its utility in open wounds. 5 Previously reviewed (Fumal, Braham et al. 2002) The beneficial toxicity paradox of antimicrobials in leg ulcer healing impaired by a polymicrobial flora: a proof-ofconcept study. International Wound Infection Institute – Evidence Matrix Two lesions in each of 51 patients with chronic leg ulcers were studied. The ulcers were long-standing but were not apparently infected. The two target ulcers were randomised to receive saline rinse and hydrocolloid (control) or control plus antimicrobial. The test antimicrobials were: 10% povidone-iodine, 1% silver sulfadiazine (SSD) or 5% chlorhexidine. After six weeks, the healing rate was slightly improved with SSD and chlorhexidine, but was significantly improved with povidone-iodine (p<0.01). Based on histological analysis, the authors suggest that the beneficial effect of povidone- Page 30 of 53 2 Author, date Comment Title Key points Grade iodine is not due just to an antimicrobial effect but to a positive effect on biological mechanisms. Previously reviewed (Wu, Crews et al. 2008) Use of chlorhexidineimpregnated patch at pin site to reduce local morbidity: the ChIPPS Pilot Trial. This study evaluated the use of chlorhexidine impregnated polyurethane dressings applied to pin sites for external fixation devices in 20 patients compared with 20 controls. There was a significantly lower rate of pin tract infections in patients who were fitted with the chlorhexidine dressings. 3 BACKGROUND: Nanocrystalline silver has both antimicrobial and anti-inflammatory properties. However, the exact mechanisms underlying these activities are not known. 3 Silver, basic science and lab experiments (Bhol and Schechter 2005) Topical nanocrystalline silver cream suppresses inflammatory cytokines and induces International Wound Infection Institute – Evidence Matrix OBJECTIVES: The objectives of this study were to assess the anti-inflammatory effects of nanocrystalline silver using a murine model of allergic contact dermatitis, compare the effects with those of tacrolimus and a high potency steroid, and to relate the effects to Page 31 of 53 Author, date Comment Title Key points Grade apoptosis of inflammatory cells in a murine model of allergic contact dermatitis. modulation of pro-inflammatory cytokines and apoptosis of inflammatory cells. METHODS: Dermatitis was induced on the ears of BALB/c mice using dinitrofluorobenzene. Topical treatment, including vehicles, 1% nanocrystalline silver cream, tacrolimus ointment and a high potency steroid, was applied once a day for 4 days. Ear swelling was measured and the erythema was evaluated daily. After 4 days of treatment the mice were killed and samples from the ears were collected for histological and immunohistochemical examination, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labelling (TUNEL) staining and extraction of total RNA for reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: Significant reductions of ear swelling, erythema and histopathological inflammation in mice ears were observed after 4 days of treatment with 1% nanocrystalline silver cream, tacrolimus ointment or a high potency steroid with no significant difference among them. Both RT-PCR and immunohistochemical staining of sections from ear biopsies demonstrated that nanocrystalline silver, tacrolimus and steroid significantly suppressed the expression of tumour necrosis factor (TNF)-alpha and and IL-12 and induces apoptosis of inflammatory cells; mechanisms by which nanocrystalline silver may exert its anti-inflammatory effects (Published abstract). (Burd, Kwok et al. 2007) A comparative study of the cytotoxicity of International Wound Infection Institute – Evidence Matrix Over the past decade, a variety of advanced silver-based dressings have been developed. There are considerable variations in the structure, composition, and silver content of these Page 32 of 53 3 Author, date Comment Title Key points Grade silver-based dressings in monolayer cell, tissue explant, and animal models. new preparations. In the present study, we examined five commercially available silverbased dressings (Acticoat, Aquacel Ag, Contreet Foam, PolyMem Silver, Urgotul SSD). We assessed their cytotoxicity in a monolayer cell culture, a tissue explant culture model, and a mouse excisional wound model. The results showed that Acticoat, Aquacel Ag, and Contreet Foam, when pretreated with specific solutes, were likely to produce the most significant cytotoxic effects on both cultured keratinocytes and fibroblasts, while PolyMem Silver and Urgotul SSD demonstrated the least cytotoxicity. The cytotoxicity correlated with the silver released from the dressings as measured by silver concentration in the culture medium. In the tissue explant culture model, in which the epidermal cell proliferation was evaluated, all silver dressings resulted in a significant delay of reepithelialization. In the mouse excisional wound model, Acticoat and Contreet Foam indicated a strong inhibition of wound reepithelialization on the postwounding-day 7. These findings may, in part, explain the clinical observations of delayed wound healing or inhibition of wound epithelialization after the use of certain topical silver dressings. Caution should be exercised in using silver-based dressings in clean superficial wounds such as donor sites and superficial burns and also when cultured cells are being applied to wounds (Published abstract). (Dunn and Edwards-Jones The role of Acticoat with nanocrystalline International Wound Infection Institute – Evidence Matrix Silver is an effective antimicrobial agent, but older silver-containing formulations are rapidly inactivated by the wound environment, requiring frequent replenishment. These older formulations may also be pro-inflammatory and may delay healing. Acticoat (Smith & Page 33 of 53 4 Author, date Comment 2004) (Fong, J. 2005). (Fraser, Bodman et al. 2004) A comparison of standard burn treatment (SSD) compared to nanocrystalline silver dressings Title Key points silver in the management of burns. Nephew, Hull, UK) is a relatively new form of silver antimicrobial barrier dressing which helps avoid the problems of earlier agents. It has rapid and sustained bactericidal activity, and because of this may reduce inflammation and promote healing. Despite extensive testing and clinical experience, no evidence has emerged of resistance or cytotoxicity to nanocrystalline silver. This article collects together a number of presentations that were given at the 2003 European Burns Association Meeting on the use of Acticoat in the management of burns (Published abstract). The use of silver products in the management of burn wounds: Change in practice for the burn unit at Royal Perth Hospital. An in vitro study of the antimicrobial efficacy of a 1% silver sulfadiazine and 0.2% chlorhexidine Details before and after patient care audits conducted in a burns unit in 2000 and 2002. The outcome variables were burn wound cellulitis, antibiotic use and cost of treatment. The two regimes audited were twice daily showers or washes with chlorhexidine 4% soap followed by the application of silver sulphadiazine cream or nanocrystalline silver (Acticoat™). The audit demonstrated reduced incidence of infection and antibiotic use as well as cost savings in the treatment of burns with nanocrystalline silver as compared to SSD. 4 Burn sepsis is a leading cause of mortality and morbidity in patients with major burns. The use of topical anti-microbial agents has helped improve the survival in these patients. There are a number of anti- 3 International Wound Infection Institute – Evidence Matrix Grade microbials available, one of which, Silvazine (1% silver sulphadiazine (SSD) and 0.2% chlorhexidine digluconate), is used only in Australasia. No study, in vitro or clinical, had compared Silvazine with the new dressing Acticoat. This study compared the anti-microbial activity of Page 34 of 53 Author, date Comment Title Key points digluconate cream, 1% silver sulfadiazine cream and a silver coated dressing. Silvazine, Acticoat and 1% silver sulphadiazine (Flamazine) against eight common burn wound pathogens. METHODS: Each organism was prepared as a suspension. A 10 microl inoculum of the chosen bacterial Grade isolate (representing approximately between 10(4) and 10(5) total bacteria) was added to each of four vials, followed by samples of each dressing and a control. The broths were then incubated and 10 microl loops removed at specified intervals and transferred onto Horse Blood Agar. These plates were then incubated for 18 hours and a colony count was performed. RESULTS: The data demonstrates that the combination of 1% SSD and 0.2% chlorhexidine digluconate (Silvazine) results in the most effective killing of all bacteria. SSD and Acticoat had similar efficacies against a number of isolates, but Acticoat seemed only bacteriostatic against E. faecalis and methicillin-resistant Staphylococcus aureus. Viable quantities of Enterobacter cloacae and Proteus mirabilis remained at 24h. CONCLUSION: The combination of 1% SSD and 0.2% chlorhexidine digluconate (Silvazine) is a more effective anti-microbial against a number of burn wound pathogens in this in vitro study. A clinical study of its in vivo anti-microbial efficacy is required (Published abstract). International Wound Infection Institute – Evidence Matrix Page 35 of 53 Author, date (Lam, Chan et al. 2004) Comment Title Key points Grade In vitro cytotoxicity testing of a nanocrystalline silver dressing (Acticoat) on cultured keratinocytes. Acticoat is a polyethylene mesh coated with nanocrystalline silver. It has been used widely as a dressing for chronic wounds, acute partial-thickness burn wounds and donor sites. In this study, the in vitro cytotoxicity of Acticoat on cultured keratinocytes is tested. Human 3 keratinocytes are cultivated on a pliable hyaluronate-derived membrane (Laserskin) using dermal fibroblasts as the feeder layer. When the cultured Laserskin (CLS) is subconfluent it is covered by Acticoat, which is exposed to water (Group 1), phosphate-buffered saline (Group 2) or culture medium (Group 3). The control group is not exposed to the Acticoat. After 30 minutes incubation at 37 degrees C, the inhibitory effect of the nanocrystalline silver on keratinocyte growth is measured by an MTT assay. Compared with the control, the relative viability of the CLS dropped to 0%, 0% and 9.3%, respectively. Thus, Acticoat is cytotoxic to cultured keratinocytes and should not be applied as a topical dressing on cultured skin grafts (Lansdown, Jensen et al. 2003) Contreet Foam and Contreet Hydrocolloid: an insight into two new silvercontaining dressings. International Wound Infection Institute – Evidence Matrix In vitro laboratory tests and preliminary clinical trials have found that two silver-containing dressings, Contreet Foam and Contreet Hydrocolloid, promote healing in infected and chronic venous leg ulcers and diabetic foot ulcers Page 36 of 53 4 Author, date (Muller, Winkler et al. 2003) (Paddle-Ledinek, Nasa et al. 2006) Comment Title Key points Grade Antibacterial activity and endotoxinbinding capacity of Actisorb Silver 220. Actisorb Silver 220 wound dressing demonstrated a high in vitro endotoxin-binding capacity 3 combined with a marked bactericidal activity without releasing Pseudomonas aeruginosa endotoxins into the environment, and so may be beneficial in the treatment of infected Effect of different wound dressings on cell viability and proliferation. Keratinocyte cultures were exposed for 40 hours to extracts of Acticoat, Aquacel-Ag, Aquacel, Algisite M, Avance, Comfeel Plus transparent, Contreet-H, Hydrasorb and SeaSorb with silicone extract as a reference. Cell survival and proliferation were measured. wounds, particularly colonization by Gram-negative bacteria.. 3 The authors found that extracts of silver-containing dressings were most cytotoxic. Extracts of Hydrasorb were less cytotoxic but affected keratinocyte proliferation and morphology. Extracts of alginate-containing dressings had high calcium concentrations which markedly reduced keratinocyte proliferation and affected morphology. Aquacel and Comfeel inhibited keratinocyte proliferation to a small but significant degree. The authors conclude that silver dressings should not be used in the absence of infection. (Poon and Burd 2004) In vitro cytotoxicity of silver: implication for International Wound Infection Institute – Evidence Matrix In this study, we look at the cytotoxic effects of silver on keratinocytes and fibroblasts. We have assessed the viability of monolayer cultures using the MTT and BrdU assays. The composition of the culture medium and also the culture technique were modified to assess Page 37 of 53 3 Author, date Comment Title Key points Grade clinical wound care. the effects of culture 'environment' on the susceptibility of the cells to the toxic action of silver. Further in vitro, experiments were performed using tissue culture models to allow cellular behavior in three dimensional planes which more closely simulated in vivo behavior. The silver source was both silver released from silver nitrate solution but also nanocrystalline silver released from a commercially available dressing. The results show that silver is highly toxic to both keratinocytes and fibroblasts in monolayer culture. When using optimized and individualized culture the fibroblasts appear to be more sensitive to silver than keratinocytes. However, when both cell types were grown in the same medium their viability was the same. Using tissue culture models again indicated an 'environmental effect' with decreased sensitivity of the cells to the cytotoxic effects of the silver. Nevertheless in these studies the toxic dose of skin cells ranging from 7 x 10(-4) to 55 x 10(-4)% was similar to that of bacteria. These results suggest that consideration of the cytotoxic effects of silver and silver-based products should be taken when deciding on dressings for specific wound care strategies. This is important when using keratinocyte culture, in situ, which is playing an increasing role in contemporary wound and burn care (Silver, Phung et al. 2006) Silver as biocides in burn and wound dressings and International Wound Infection Institute – Evidence Matrix Silver products have been used for thousands of years for their beneficial effects, often for hygiene and in more recent years as antimicrobials on wounds from burns, trauma, and diabetic ulcers. Silver sulfadiazine creams (Silvazine and Flamazine) are topical ointments Page 38 of 53 5 Author, date Comment Title Key points Grade bacterial resistance to silver compounds. that are marketed globally. In recent years, a range of wound dressings with slow-release Ag compounds have been introduced, including Acticoat, Actisorb Silver, Silverlon, and others. While these are generally accepted as useful for control of bacterial infections (and also against fungi and viruses), key issues remain, including importantly the relative efficacy of different silver products for wound and burn uses and the existence of microbes that are resistant to Ag+. These are beneficial products needing further study, although each has drawbacks. The genes (and proteins) involved in bacterial resistance to Ag have been defined and studied in recent years (Published abstract). (Supp, Nelly et al. 2005) Evaluation of cytotoxicity and antimicrobial activity of Acticoat burn dressing for management of microbial contamination in cultured skin substitutes grafted to athymic mice. International Wound Infection Institute – Evidence Matrix This study evaluated the cytotoxicity and microbial efficacy of Acticoat when used with cultured skin substitutes (CSS) which are often used in the closure of burn wounds. CSS was grafted to full-thickness wounds in athymic mice. The cytotoxicity of the dressing was evaluated after one week of exposure during in vitro maturation, or by assessment of healing on the mice. After four weeks, wound biopsies were evaluated for engraftment of human cells. In a subsequent experiment wounds were inoculated with P aeruginosa before application of CSS. The authors found that, in vitro, Acticoat was cytotoxic to CSS within one day, but in vivo, one week of exposure did not injure CSS or inhibit wound healing. Contaminated wounds treated with Acticoat healed similarly to control treatments, with comparable rates of engraftment. None of the test strain of P aeruginosa was found in the wound after Page 39 of 53 3 Author, date Comment Title Key points Grade inoculation onto the surface of Acticoat. They conclude that Acticoat may be effective as a protective dressing to reduce environmental contamination of CSS, but suggest that additional antimicrobials may be required to control organisms in the wound (Published abstract) (Thomas and McCubbin 2003) An in vitro analysis of the antimicrobial properties of 10 silver-containing dressings. The authors were interested to examine how dressings with different silver content and composition might release silver in sufficiently high concentrations to exert a significant antimicrobial effect. An earlier study investigated Acticoat, Actisorb Silver 220, Avance and Contreet-H and these were included along with six new dressings: Arglaes, Aquacel Ag, Calgitrol, Contreet Ag, Silverlon, Silvasorb and the test organisms were: S aureus, E coli and Candida albicans. 3 Four measurements were taken: zone of inhibition, microbial challenge, microbial transmission and silver content. Full details of the performance of the ten dressings can be found in the article. As the results vary between test and organism it is impossible to reproduce all the results here, however, Acticoat, Aquacel Ag, Calgitrol Ag, Contreet-H and Silverlon generally performed better than other dressings. The results can be loosely related to silver content, but the form and location of the silver also have an effect on performance. (Wright, Lam et al. 2002) Early healing events in a International Wound Infection Institute – Evidence Matrix Full thickness wounds on the backs of pigs, contaminated with P aeruginosa, Fusobacterium species and coagulase-negative staphylococci were covered with dressings, some of which Page 40 of 53 3 Author, date Comment Title Key points Grade porcine model of contaminated wounds: effects of nanocrystalline silver on matrix metalloproteina ses, cell apoptosis and healing. contained silver. Comparative evaluation of silver-containing antimicrobial dressings and drugs. Wound dressings containing silver as antimicrobial agents are available in various forms and 3 formulations; however, little is understood concerning their comparative efficacy as antimicrobial agents. Eight commercially available silver-containing dressings, Acticoat 7, Acticoat Moisture Control, Acticoat Absorbent, Silvercel, Aquacel Ag, Contreet F, Urgotol SSD and Actisorb, were tested to determine their comparative antimicrobial effectiveness in vitro and compared against three commercially available topical antimicrobial creams, a non treatment control, and a topical silver-containing antimicrobial gel, Silvasorb. Zone of inhibition and quantitative testing was performed by standard methods using Escherichia Nanocrystalline silver dressings promoted rapid wound healing, particularly in the days immediately after injury. There was rapid development of well vascularised granulation tissue that was able to take a tissue graft four days after injury. Control wounds were not able to take a graft. The proteoloytic environment of the wounds dressed with nanocrystalline silver dressings had reduced levels of matrix metalloproteinases and higher levels of cellular apoptosis. The authors suggest that nanocrystalline silver may alter the inflammatory events in wounds and facilitate the early phase of wound healing. Silver, clinical (Castellano, Shafii et al. 2007) International Wound Infection Institute – Evidence Matrix Page 41 of 53 Author, date Comment Title Key points Grade coli, Pseudomonas aeruginosa, Streptococcus faecalis and Staphylococcus aureus. Results showed all silver dressings and topical antimicrobials displayed antimicrobial activity. Silvercontaining dressings with the highest concentrations of silver exhibited the strongest bacterial inhibitive properties. Concreet F and the Acticoat dressings tended to have greater antimicrobial activity than did the others. Topical antimicrobial creams, including silver sulfadiazine, Sulfamylon and gentamicin sulfate, and the topical antimicrobial gel Silvasorb exhibited superior bacterial inhibition and bactericidal properties, essentially eliminating all bacterial growth at 24 hours. Silver-containing dressings are likely to provide a barrier to and treatment for infection; however, their bactericidal and bacteriostatic properties are inferior to commonly used topical antimicrobial agents (Published abstract). (Holder, Durkee et al. 2003) Assessment of a silver-coated barrier dressing for potential use with skin grafts on excised burns. Acticoat burn dressing is a silver-coated dressing with antimicrobial activity purported to reduce infection from environmental organisms in partial and full-thickness wounds. Acticoat was tested for activity as an antimicrobial treatment and as an antimicrobial barrier dressing in three in vitro assays. It was found that a modified disc assay method gave false negative results but in an assay in which bacteria were inoculated on top of samples of Acticoat, bacterial numbers were reduced, over time, with all microorganisms tested. Acticoat served as a barrier for bacteria, inoculated onto it, from contaminating the surface of an agar plate under the Acticoat. The data show that Acticoat has: antimicrobial capabilities, but to be effective hours of contact between Acticoat and the microorganisms are required; and the capacity to serve as an antimicrobial barrier dressing. These findings support the conclusion that Acticoat has activity to reduce microbial contamination of wounds from environmental sources. International Wound Infection Institute – Evidence Matrix Page 42 of 53 3 Author, date (Rustogi, Mill et al. 2005) Comment Title Key points Grade The use of Acticoat in neonatal burns. PURPOSE: To evaluate the safety and efficacy of Acticoat use in primary burn 4 injuries and other skin injuries in premature neonates. PROCEDURES: An audit of eight premature neonates who sustained burn injuries and other cutaneous injuries from various agents were treated with Acticoat. Serum silver levels were measured in three neonates. Wounds were assessed for infection and blood cultures were taken where sepsis was suspected. FINDINGS: Neonates ranged from 23 to 28 weeks gestation (weight: 578-1078 g). Causative injury mechanisms included: alcoholic chlorhexidine, alcoholic wipes, electrode jelly, extravasated intravenous fluids, artery illuminator, temperature probe and adhesive tape removal. Total burned body surface area ranged from 1 to 30%. All neonates were treated with Acticoat dressing changed every 3-7 days. All wounds re-epithelialised by day 28 and scar management was not required. There were four mortalities secondary to problems associated with extreme prematurity. Serum silver levels ranged from 0 to 1 micromol/L. There were no wound infections or positive blood cultures during the treatment period. CONCLUSIONS: Acticoat is a suitable dressing for premature neonates who have sustained burn injury, with the advantage of minimal handling as the dressing need only be changed every 3-7 days (Published abstract). International Wound Infection Institute – Evidence Matrix Page 43 of 53 Author, date (Tredget, Shankowsky et al. 1998) Comment Title A matched-pair, randomized study evaluating the efficacy and safety of Acticoat silvercoated dressing for the treatment of burn wounds. International Wound Infection Institute – Evidence Matrix Key points Grade A new silver-coating technology was developed to prevent wound adhesion, limit 2 nosocomial infection, control bacterial growth, and facilitate burn wound care through a silver-coated dressing material. For the purposes of this article, Acticoat (Westaim Biomedical Inc, Fort Saskatchawan, Alberta, Canada) silver-coated dressing was used. After in vitro and in vivo studies, a randomized, prospective clinical study was performed to assess the efficacy and ease of use of Acticoat dressing as compared with the efficacy and ease of our institution's standard burn wound care. Thirty burn patients with symmetric wounds were randomized to be treated with either 0.5% silver nitrate solution or Acticoat silver-coated dressing. The dressing was evaluated on the basis of overall patient comfort, ease of use for the wound care provider, and level of antimicrobial effectiveness. Wound pain was rated by the patient using a visual analog scale during dressing removal, application, and 2 hours after application. Ease of use was rated by the nurse providing wound care. Antimicrobial effectiveness was evaluated by quantitative burn wound biopsies performed before and at the end of treatment. Patients found dressing removal less painful with Acticoat than with silver nitrate, but they found the pain to be comparable during application and 2 hours after application. According to the nurses, there was no statistically significant difference in the ease of use. The frequency of burn wound sepsis (> 10(5) organisms per gram of tissue) was less in Acticoat-treated wounds than in those treated with silver nitrate (5 vs 16). Secondary bacteremias arising from infected burn wounds were also less frequent with Acticoat than with silver nitrate-treated wounds (1 vs 5). Acticoat dressing offers a new form of dressing for the burn wound, but it requires further investigation with greater numbers of patients in a larger number of centers and in different Page 44 of 53 Author, date Comment Title Key points Grade phases of burn wound care (Published abstract). (Wright, Lam et al. 1999) Efficacy of topical silver against fungal burn wound pathogens. BACKGROUND: Fungal infections of burn wounds have become an important cause of burn- 3 associated morbidity and mortality. The nature of fungal infections dictates aggressive treatment to minimize the morbidity associated with these infections. Persons with large total body surface area burns are particularly susceptible to fungal infections and are treated in such a manner as to minimize their risk of infection. METHODS: This study examined the in vitro fungicidal efficacy of a variety of different topical agents. By placing fungal inocula in contact with mafenide acetate, silver nitrate, silver sulfadiazine, and a nanocrystalline silver-coated dressing, we determined the kill kinetics of these topical agents against a spectrum of common burn wound fungal pathogens. RESULTS: The topical antimicrobials that were tested demonstrated varying degrees of efficacy against these pathogens. CONCLUSION: The nanocrystalline silver-based dressing provided the fastest and broadest-spectrum fungicidal activity and may make it a good candidate for use to minimize the potential of fungal infection, thereby reducing complications that delay wound healing (Published abstract). International Wound Infection Institute – Evidence Matrix Page 45 of 53 References Apelqvist, J. and T. Ragnarson (1996). "Cavity foot ulcers in diabetic patients: a comparative study of cadexomer iodine ointment and standard treatment. An economic analysis alongside a clinical trial." Acta Derm Venereol 76(3): 231-5. Apelqvist, J. and T. 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International Wound Infection Institute – Evidence Matrix Page 52 of 53 Acknowledgements: The IWII is very grateful to the following members for the development of this matrix: Dr Keryln Carville, Curtin University of Technology, Australia Terry Swanson, South West Healthcare, Warrnambool, Victoria, South Australia Dr Marc Despatis, Cape Breton Health Care Complex, Canada Jude Douglass, IWII Member, UK International Wound Infection Institute – Evidence Matrix Page 53 of 53