Corroding characteristics of Eikenella corrodens

Fourteen strains of Eikenella corrodens isolated from human oral cavity were studied to determine corroding characteristics. Nine out of the 14 strains produced corroding colonies under anaerobic culture condition. One of them produced corrosion even in an aerobic culture. No morphological differences in surface structures were observed between corroding and non-corroding strains of E. corrodens by transmission electron microscopy. The morphology of corroding colonies of E. corrodens was then examined by scanning electron microscopy. The surface of the corroding-colony center was smoothly convex. A boundary line was clear between the smooth center and the surrounding corrosion region. Double or triple frill-like structures surrounded the center portion with small convexities. Spreading bacterial masses were observed in the outer portion of the colony. Morphological observations of the corroding colony edge indicated that a surface translocation termed "twitching motility" or "gliding motility" occurs in the outer portion and plays a role in its colonization of periodontal regions.