LAUSR

More important to wound care providers is this group, including individuals from across Europe and the US, used chronic wounds as one of their two examples of a biofilm infection, as evidence that biofilms are ubiquitous in human chronic non-healing wounds keeps increasing.2,3 That a chronic wound should be viewed as a chronic infection is well documented science for the ESMID group4,5 and as Terry Swanson reports in her survey in this issue (page 426), most wound care providers are in agreement with chronic wounds as biofilm infections at many levels. For one survey question ‘The presence of biofilm can be a barrier to wound healing’ over 90% of respondents indicated that they believed the statement is true/think this is true. Furthermore, it is also true that microbes, even growing as biofilm, which cause harm to the patient such as interfering with wound healing are causing a genuine infection. But biofilm infections are quite different to the single microbe infections (acute infections) with which we are familiar. Briefly, biofilm is a different strategy microbes use to survive, a different mode of growth and a different pattern of gene expression. In a biofilm, up to one third of the microbe’s genome (~800 previously dormant genes) are expressed.6 The newly expressed genes and gene products are responsible for tolerance to antibiotics,7 causing persistent inflammation8 and effective evasion of host adaptive and innate immunity.9 Yet no single gene or gene product can be used to identify microbes growing as a biofilm. A biofilm is usually composed of several different microbial species (polymicrobial)10 that cooperate (synergy)11 to cause infection. The variable microbial species which makes up the biofilm once attached (any tissue/ organ in the body can be infected with biofilm) the biofilm diffuses and injects through multiple secretion systems agents.12 These secretions are most often small peptides which render host cells senescent (alive but not functioning correctly), white blood cell dysfunction and persistent inflammation. A biofilm infection is parasitic in strategy and tries to maintain a sustainable niche for a long duration requiring the microbial community to subvert host healing pathways. The behaviours of a chronic wound, which we see every day in the clinic, such as exudate, slough and impaired healing can easily be explained by the natural infection methods of biofilm. The wound microbiota producing infection, mainly biofilm infection, is an important cause of chronic wounds and this barrier must be effectively managed. Wound care providers currently use many different antimicrobial strategies (antibiotics, biocides, physical disruption) by different methods (equipment, topical, systemic) with only small improvement in outcomes. The biggest barrier to effective biofilm management is that the main diagnostic tool, clinical culture is ill suited for diagnosing (microbial identification) biofilm infections.13 Culture methods are over 150 years old and are not designed for biofilm infection because biofilms are usually multiple species in a mode where the microbial cells are alive but will not replicate in culture conditions (viable but will not divide so can not be cultured). Because of the severe inadequacies of culture methods wound care providers have evolved into a trial and error paradigm for antimicrobial management. Environmental and many other branches of microbiology long ago turned to nonculture methods to identify biofilm bacteria. Methods using the polymerase chain reaction (PCR), sequencing and mass spectrometry are now superior to culture and allow specific diagnosis and accurate monitoring of antimicrobial treatments. Dr Rennie reports in this issue (page 452) a possible new diagnostic hand held tool which identifies molecules excitable by a specific wavelength of light that are unique to bacterial species. This may allow for point-of-service diagnosis of if/where bacteria or in the wound. New and multiple microbial diagnostics will pave the way for more effective wound care treatments. The current method of trying a single product then sequentially progressing through individual products in an ad hoc manner must give way to a solid scientific diagnose followed by a treatment standard. Modern medicine demands wound care to make this change. A once and done treatment regimen of antibiotics, an antimicrobial dressing or physical agents will rarely be enough to treat a biofilm infection. The nature of biofilm infection requires more than a single treatment strategy. Emerging wound care methodologies use multiple treatments targeting the wound microbiota which are used synergistically to collapse the wound biofilm. Treatments such as sharp debridement, agents that degrade the biofilm matrix, agents that block biofilm communications (quorum sensing inhibitors), methods to rapidly remove exudate thus robbing the biofilm of nutrients, bactericidal agents and antibiotics are carefully chosen based on diagnostic identification of the wound microbiota and so as not to negatively interact. This treatment strategy for wounds is similar to many cancer treatments which start with maximum therapy using multiple agents and then deescalating (stopping individual agents/treatments) as Randall D Wolcott, Founder, Southwest Regional Wound Care Center