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 c ystic fibrosis. The purpose of this study was to examine wounds for the For mation of bacterial biofilms. partial-thickness wounds were mode on three p igs with a dermatome. Wounds were challenged with Pseudomonas aeruginosa an d 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 sc rubbed samples were plated on Pseudomonas isolation agar for quantitation. Cover slips were removed from the wounds at 72 hours, and wound curettage w as obtained. Congo red staining procedure, which detects EPS, was used to s tain 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 populat ion had a narrower range suggesting a critical mass for those bacteria that were adherent to the wound. This preliminary work has demonstrated that ba cterial biofilms do form in wounds. This in-vivo assay system will provide a means to examine therapeutic modalities for bacteria living in a protecti ve biofilm.