Infinite serovar and ribotype heterogeneity among oral Fusobacterium nucleatum strains?

Fusobacterium nucleatum is part of the residential human microbiota and is associated with various infections. It is characterised by broad genetic he terogeneity, but reliable phenotypic markers are lacking. The purpose of th e present study was to generate antibodies for the detection of F. nucleatu m, to characterise expression patterns of the detected surface antigens on oral isolates, to investigate the prevalence of distinguishable subtypes in clinical samples from the oral cavity, and to compare antigenic with ribot ype heterogeneity. Thirty-seven monoclonal antibodies (mAbs) were generated and characterised using strains from 52 taxa. Antibody-binding bacteria we re monitored in 35 samples of supra- and subgingival plaque from healthy si tes and sites affected by gingivitis or periodontitis. Results indicated br oad but structured antigenic heterogeneity. Detecting at least 28 different epitopes, the mAbs defined 19 serovars. Epitopes were expressed on perioda te-sensitive polysaccharide chains. Ribotyping of 40 oral F. nucleatum stra ins (PvuII digestion) resulted in the detection of similarly broad genetic heterogeneity, which rarely corresponded to the observed phenotypic diversi ty. Clinical samples were generally positive for multiple (up to eight) ser ovars of which some colonised supra- and subgingival plaques from both heal thy and diseased sites, whereas others were restricted to inflamed sites. T he majority of the studied isolates could not be grouped with reference str ains of the five established subspecies of F. nucleatum, corroborating doub ts about the usefulness of the current classification scheme. Although, as a whole the described monoclonal antibodies can only recognise a part of th e overwhelming heterogeneity of this 'species', they should prove of value to investigations of the importance, the antigenic stability and the origin of positive subtypes of F, nucleatum from human infections. (C) 1999 Acade mic Press.