BACKGROUND. In chronic wounds, biofilms probably play a vital role in protecting bacteria from host defenses and antimicrobial medications by creating a barrier of exopolysaccharide that is difficult for the immune system and antibiotics to penetrate. A biofilm consists of an exopolysaccharide matrix that is produced and secreted by certain species of bacteria. OBJECTIVE. The purpose of this study was to visualize and time the progressing growth of a biofilm by a wound-isolated Pseudomonas aeruginosa. METHODS. P. aeruginosa that was initially isolated from a human burn wound was allowed to grow a biofilm in vitro. We used a modified Congo red staining technique to demonstrate the sequential development of a mature biofilm as examined by light microscopy. RESULTS. We show that the exopolysaccharide of the developing biofilm is visible in just 5 hours after inoculation and has the characteristics of a mature biofilm by 10 hours. CONCLUSION. The rapidity of biofilm growth suggests that bacteria in wounds possess the capacity of producing this shield against antibiotics and immune effector cells early in the infection process. Therefore, efforts to prevent or slow the proliferation of bacteria and biofilms should occur soon after a wound is created. Additionally, this staining technique can be used to demonstrate the ability of agents to slow biofilm growth or to interrupt formed biofilm and may be useful in future studies of chronically infected wounds.
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