CLINICAL AND MICROBIOLOGICAL FEATURES OF REFRACTORY PERIODONTITIS SUBJECTS

The purpose of this investigation was to compare the clinical paramete rs and the site prevalence and levels of 40 subgingival species in suc cessfully treated and refractory periodontitis subjects. 94 subjects r eceived scaling and root planing and if needed, periodontal surgery an d systemically administered tetracycline. 28 refractory subjects showe d mean full mouth attachment loss and/or >3 sites showing attachment l oss >2.5 mm within 1 year post-therapy 66 successfully treated subject s showed mean attachment level gain and no sites with attachment loss >2.5 mm. Baseline subgingival plaque samples were taken from the mesia l aspect of each tooth and the presence and levels of 40 subgingival t axa were determined using whole genomic DNA probes and checkerboard DN A-DNA hybridization. The mean levels and % of sites colonized by each species (prevalence) was computed for each subject and differences bet ween groups sought using the Mann-Whitney test. Most of the 40 species tested, including Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola and Bacteroides forsythus, were equal ly or less prevalent in the refractory group. Prevotella nigrescens wa s significantly more prevalent in successfully treated subjects, while refractory subjects harbored a larger proportion of Streptococcus spe cies, particularly Streptococcus constellatus. The odds of a subject b eing refractory was 8.6 (p<0.001) if S. constellatus constituted great er than or equal to 3.5% of the total DNA probe count. Since few micro biological differences existed between treatment outcome groups using DNA probes to known species, the predominant cultivable microbiota of 33 subgingival samples from 14 refractory subjects was examined. 85% o f the 1649 isolates were identified using probes to 69 recognized subg ingival species. The remaining unidentified strains were classified by analyzing 16S rRNA gene sequences. Many sequenced isolates were of ta xa not considered a common part of the oral microbiota such as Acineto bacter baumanni, Gemella haemolysans, Enterococcus faecalis, Staphyloc occus warneri, Pseudomonas aeruginosa and novel species in the genera Bartonella, Ralstonia, Neisseria, Eubacterium, Rothia, Gordona, Gemell a, Corynebacterium, Leptotrichia, and Actinomyces. Refractory subjects constituted a heterogeneous group based on their subgingival microbio ta. As a group, they did not harbor more of the ''classic'' periodonto pathogens, although elevated proportions of S. constellatus were found .