Lifestyles of bacteria in wounds: Presence of biofilms?

Biofilms consist of bacteria and other organisms that live within a matrix of extracellular polysaccharide (EPS) and have been implicated in bacterial diseases, such as otitis media, dental plaque, and chronic infections in cystic fibrosis. The purpose of this study was to examine wounds for the Formation of bacterial biofilms. partial-thickness wounds were mode on three pigs with a dermatome. Wounds were challenged with Pseudomonas aeruginosa and covered with either a polyurethane dressing or plastic cover slip. At 72 hours, each wound was vigorously flushed three times with sterile saline to dislodge any non-adherent bacteria. The flushed wounds were then cultured with a surfactant solution using a scrub technique. Both the flushed and scrubbed samples were plated on Pseudomonas isolation agar for quantitation. Cover slips were removed from the wounds at 72 hours, and wound curettage was obtained. Congo red staining procedure, which detects EPS, was used to stain both cultures. A thick, dark red to yellow-orange amorphous EPS matrix was seen surrounding bacteria, indicating a biofilm. Wounds cultured with saline or surfactant demonstrated that there were two distinct populations of bacteria living in the wound area. The non-adherent population displayed a quantitative variation from wound to wound, whereas the adherent population had a narrower range suggesting a critical mass for those bacteria that were adherent to the wound. This preliminary work has demonstrated that bacterial biofilms do form in wounds. This in-vivo assay system will provide a means to examine therapeutic modalities for bacteria living in a protective biofilm.