Serum antibody titers to Bacteroides forsythus in elderly subjects with gingivitis or periodontitis

Background: The risks for periodontal disease appear to increase with age. Study purpose: To determine associations between clinical findings, the pre sence of specific bacteria in periodontal pockets, and serum antibody titer s. 10 older subjects (mean age = 73.0 years SD+/-4.9) with confirmed gingiv itis only (gingivitis group) and 10 subjects with periodontitis (mean age: 76.1 years, SD+/-10.4) (periodontitis group) were studied. Results: The mean group differences for probing depth and clinical attachme nt levels were 4.1 mm and 5.6 mm, respectively, and were significantly diff erent (p<0.001). Both groups had high plaque scores (>60% surfaces with pla que). DNA probes demonstrated that B. forsythus was present in 8/10 samples from the periodontitis group and in 7/10 samples from the gingivitis group . The B. forsythus isolates studied were found in four of the subjects with periodontitis and from 2 of the subjects with gingivitis. Serum antibody t iters to 6 ribotypes of B. forsythus were studied. Western blots, gradient gels, and pulsed field gel electrophoresis concurrently demonstrated that t he B. forsythus isolates were genotypically, and phenotypically unique for each subject. Antibody titers to two selected B. forsythus isolates were si gnificantly higher in the periodontitis group (p<0.01, Mann-Whitney test). The study confirmed that antibody serum titers to the six different ribotyp es of B. forsythus varied greatly between older individuals with gingivitis or periodontitis. Not all strains of B. forsythus elicited higher titers i n periodontitis affected subjects. Conclusions: The results of the present study suggest genotype variation of B. forsythus that is unique to the individual and that serotype variation can be expected. It is possible that B. forsythus under specific host condi tions can modulate surface antigen factors to evade the host immune respons e.