Recent studies have indicated that bacteria producing a large amount of extracellular polysaccharides cause persistent infections. However, the exact distribution of the biofilm-forming bacteria in acute periodontal lesions remains poorly understood. To estimate the number of biofilm-forming bacteria in periodontal pockets, we isolated and identified the bacteial strains of plaque samples collected from four patients with acute periodontitis. Forty bacterial strains that were isolated produced viscous materials in their spent culture media and possessed meshwork-like structures on their cell surfaces. These included three anaerobic rods, one anaerobic coccus, three facultative anaerobic rods, one facultative anaerobic coccus, and one microaerophilic rod. These results suggest that many oral bacteria found in subgingival plaque have the ability to produce viscous materials resulting in the formation meshwork structures.
