Bacteria reactive to plaque-toxin-neutralizing monoclonal antibodies are related to the severity of gingivitis at the sampled site.

Certain monoclonal antibodies (Mabs) neutralize the inhibition of HL60 cell growth by bacterial plaque extracts. The aim of this study was to enumerate and identify the bacteria reactive to these Mabs at sites where periodontal disease was measured by gingival index, pocket depth and attachment loss. The bacterial colonies were grown on blood agar and the colonies counted directly and after immunoblotting. Sites that bled on probing (n = 15) had a mean of 3.35% Mab-positive colonies (SEM = 0.52%) and sites that did not bleed (n = 9) had a mean of 1.61% (SEM = 0.41%). The percentage of Mab-positive colonies also correlated with gingival index but not with the total number of colonies sampled, attachment loss or pocket depth. Antigen was expressed by 4 genera: strains of Streptococcus sanguis and/or Eikenella corrodens (8 sites), Staphylococcus epidermidis (4 sites) and Corynebacterium minutissimus (1 site). The results suggest that the antigens detected on these bacteria by the Mabs may be processed to form toxins and maintain gingivitis by irritating the surrounding cells.