An in vitro model of chronic wound biofilms to test wound dressings and assess antimicrobial susceptibilities

• Published in: Journal of antimicrobial chemotherapy Vol. 65; no. 6; pp. 1195 - 1206
• Main Authors: Hill, Katja E., Malic, Sladjana, McKee, Ruth, Rennison, Tracy, Harding, Keith G., Williams, David W., Thomas, David W.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.06.2010; Oxford Publishing Limited (England)
• Subjects: Anti-Bacterial Agents - pharmacology; Anti-Infective Agents, Local - pharmacology; antibiotic resistance; Antibiotics; Antibiotics. Antiinfectious agents. Antiparasitic agents; Bacteria; Bacteria - drug effects; Bacteria - growth & development; Bacteria - isolation & purification; Bandages; biocide resistance; Biofilms; Biofilms - drug effects; Biofilms - growth & development; Biological and medical sciences; chronic venous leg ulcer; Ciprofloxacin - pharmacology; coaggregation; constant depth film fermenter; Effects; Floxacillin - pharmacology; Genotype & phenotype; Humans; lactoferrin; Medical sciences; Microbial Sensitivity Tests - methods; Microscopy - methods; Microscopy, Electron, Scanning - methods; Pharmacology. Drug treatments; Povidone-Iodine - pharmacology; Pseudomonas; Pseudomonas - drug effects; Pseudomonas - growth & development; Pseudomonas - isolation & purification; Scanning electron microscopy; Silver - pharmacology; Staphylococcus; Staphylococcus - drug effects; Staphylococcus - growth & development; Staphylococcus - isolation & purification; Staphylococcus infections; Wound Infection - drug therapy; Wound Infection - microbiology; Skin disease; biocide resistance; Drug susceptibility test; Film; Lower limb; Wound; Depth; Dressing; constant depth film fermenter; Lactoferrin; Test; antibiotic resistance; Vein; Biocide; Leg ulcer; chronic venous leg ulcer; Fermenter; coaggregation; In vitro; Resistance; Antibiotic; Chronic; Sensitivity resistance; Biofilm; Medical device; Models; Antibacterial agent
• ISSN: 0305-7453; 1460-2091; 1460-2091
• DOI: 10.1093/jac/dkq105

Objectives The targeted disruption of biofilms in chronic wounds is an important treatment strategy and the subject of intense research. In the present study, an in vitro model of chronic wound biofilms was developed to assess the efficacy of antimicrobial treatments for use in the wound environment. Methods Using chronic wound isolates, assays of bacterial coaggregation established that aerobic and anaerobic wound bacteria were able to coaggregate and form biofilms. A constant depth film fermenter (CDFF) was used to develop wound biofilms in vitro, which were analysed using light microscopy and scanning electron microscopy. The susceptibility of bacteria within these biofilms was examined in response to the most frequently prescribed ‘chronic wound’ antibiotics and a series of iodine- and silver-containing commercial antimicrobial products and lactoferrin. Results Defined biofilms were rapidly established within 1–2 days. Antibiotic treatment demonstrated that mixed Pseudomonas and Staphylococcus biofilms were not affected by ciprofloxacin (5 mg/L) or flucloxacillin (15 mg/L), even at concentrations equivalent to twice the observed peak serum levels. The results contrasted with the ability of povidone–iodine (1%) to disrupt the wound biofilm; an effect that was particularly pronounced in the dressing testing where iodine-based dressings completely disrupted established 7 day biofilms. In contrast, only two of six silver-containing dressings exhibited any effect on 3 day biofilms, with no effect on 7 day biofilms. Conclusions This wound model emphasizes the potential role of the biofilm phenotype in the observed resistance to antibiotic therapies that may occur in chronic wounds in vivo.