5 Identification and characterization of biofilm forming facultative anaerobic Gram-negative rods isolated from a therapy-resistant apical periodontitis lesion

Abstract

I identified viscous-material-producing facultative anaerobic Gram-negative rods that were isolated from a therapy-resistant apical periodontitis lesion as Escherichia hermannii strains. I named them E. hermannii strains 11-1 to 6. These bacteria were surrounded by mesh-like structures which are typical of biofilm-forming bacteria. The culture medium of strain 11-2 had the highest viscosity of the six strains. When I purified exopolysaccharide (EPS) from this culture medium and analyzed its chemical composition, I found it consisted primarily of polysaccharide that contained 80% mannose. Susceptibilities of these strains to anti-microbial agents did not show any particular pattern. My data suggests that E. hermannii, a transient bacterium in the oral cavity, might form biofilm in the periapical region and cause therapy-resistant apical periodontitis.