Sulfate-reducing bacteria in association with human periodontitis

Background, aims: Sulfate-reducing bacteria (SRB) may be etiologically involved in destructive periodontal diseases. These strictly anaerobic bacteria utilize fermentation products for energy conservation by reduction of sulfate to sulfide. This toxic product can accumulate in periodontal pockets in concentrations causing cellular destruction. SRB depend on an actively degrading microbiota to produce a reduced environment, fermentation products and sulfate. The detection frequency of these bacteria is strongly increased in periodontitis compared with healthy sites in the oral cavity. Method: In this study, the presence of SRB was determined in relation to clinical features of the patients and to site-specific clinical parameters of periodontitis, such as pocket depth, bleeding and attachment level. Patients with clinical characteristics of severe periodontitis (n=87) were included in the study, 78 were untreated patients and 9 patients were in maintenance care after treatment. Samples were taken (n=261) from the deepest periodontal pockets, and presence of SRB was determined by enrichment culture in an anoxic chamber. Results: In 64% of the patients, SRB were present in at least 1 pocket. They occurred among patients from 23 to 57 years old, and tended to prevail among patients older than 30 years. There was a tendency to increased SRB occurrence among patients with more than 50% of bleeding sites, or with several angular bony defects or furcations. In 44% of the periodontal pockets SRB were present. They tended to prevail in pockets showing bleeding on probing, furcations, angular bony defects, or an endodontal complication. Presence of SRB was positively correlated with increased pocket depth (p<0.05). SRB were found to be associated with various clinical categories of periodontitis, including early onset periodontitis, rapidly progressive periodontitis, adult periodontitis, and refractory periodontitis. Although SRB predominated among patients with an adult form of periodontitis, i.e., with an occurrence of 72%, there was no significant correlation with age of the patient. Among treated patients under maintenance care, SRB prevalence was significantly reduced in comparison with untreated patients (p<0.02). Occurrence of SRB in periodontal pockets showed an odds ratio of 11.2 in comparison with healthy oral sites. Conclusion: Periodontal sulfate-reducing bacteria are associated with several clinical categories of periodontitis and with periodontal sites of increased pocket depth.