Clinical Experience with Wound Biofilm and Management: A Case Series
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Despite attaching firmly to wound tissue, biofilm can be carefully peeled away without causing damage to underlying tissue. Although biofilm will reform, a protocol of care that includes its repeated removal is likely to support wound progression over time.
Biofilm and alginate. In the cases described, the use of a silver-containing alginate dressing coincided with the rapid development of viscous, green-colored exudate; P. aeruginosa commonly was implicated. Although silver is used for antimicrobial protection, in this study it was observed that use of the silver alginate dressing was associated with the formation of thick, green exudate. Clinicians may want to consider 1) why silver (and in some cases, systemic antibiotics) appears to be ineffective as an antimicrobial agent in certain situations; 2) whether exudate may be too viscous to trigger release of the silver ions from the alginate dressing; and 3) whether exudate absorption is compromised by the quantity of the fluid (in each case the dressing looked like a wet blanket over the wound, but even a wet blanket can bleed its dye) or the presence of biofilm (ie, viscous alginate exopolysaccharide produced by P. aeruginosa).
Possibly, dressing components (eg, alginate and calcium) could have contributed to formation of the viscous exudate. In the authors’ scientific experience, alginate has been found to be an important component of biofilm EPS (notably in the presence of P. aeruginosa), rendering it hydrophobic, robust, and difficult to disperse. Calcium likely strengthens the bonds between alginate polysaccharide chains in the EPS8 and enhances pyocyanin production in P. aeruginosa.11 A base wound pH likely enhances fluorescence of the P. aeruginosa-produced fluorescein dye, inducing a bright green-blue-yellow coloration in the wound. Interestingly, with regard to silver, one in vitro study12 demonstrated the ability of silver ions to disrupt the biofilm (EPS) structure formed by Staphylococcus epidermidis at low concentration (50 parts per billion). However, regarding the current case studies, clinical wound conditions such as viscosity of the EPS produced by P. aeruginosa may have compromised the ability of the silver dressing to interact with and combat biofilm bacteria.
Biofilm and MMPs. In the cases described, the slimy, cloudy film often seemed to be associated with wounds that did not exhibit clinical signs of infection but appeared to be fighting something that manifested as persistent inflammation. This observation may relate to the state of “silent infection” or “critical colonization,” a concept described as a state in which bacteria are established within a biofilm community and compromise wound healing without inducing clear signs of clinical infection.13
Inflammation, a natural and essential part of any healing process, manages potential infection and clears the wound of devitalized tissue. However, clinical studies have shown that chronic wounds often exist in a prolonged inflammatory state involving elevated pro-inflammatory cytokine, proteinase, and oxidative activity — all of which may play a role in delayed wound healing.5 It is widely acknowledged that pathogenic bacteria stimulate inflammation through activation and proliferation of macrophages and pro-inflammatory cytokines.14,15 Recently, biofilm has been considered to be a primary cause of the prolonged inflammation that exists in chronic wounds16 and the cause of silent chronic inflammation in hemodialysis patients due to repeated stimulation of macrophages.17 The persistence of biofilm in chronic wounds may be associated with elevated production of proteinases (MMPs) and subsequent delayed healing.
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