Detection of sulphate-reducing bacteria in human saliva

Objective. The aim of the current study was to investigate the presence of sulphate-reducing bacteria (SRB) in human saliva and correlate with oral and systemic conditions. Methods. Saliva samples were collected from 118 patients and inoculated in 2 ml of modified Postgate's E medium culture. After 28 days of incubation at 30 degrees C the presence of SRB was identified by the production of sulphide. Results. Of 118 saliva samples collected, 35 were positive for the presence of SRB. Three positive samples were randomly chosen to identify the species of SRB by PCR and sequenced. The three selected samples were identified as Desulfovibrio fairfieldensis, Desulfovibrio desulfuricans and Raoultella ornithinolytica. Gastritis (14.4%) was the most prevalent systemic disease, followed by diabetes (3.4%), while periodontitis (11%) and traumatic fibroma (4.2%) were the oral manifestations most frequently found. A bivariate analysis was performed to examine for the presence of SRB and the most prevalent systemic and oral manifestations. Only periodontitis showed a statistically significant association (p = 0.0003). Conclusions. The results showed SRB can be found in oral microbiota of healthy patients. Regarding the several conditions studied, there was a higher prevalence of SRB in patients with gastritis and patients with periodontal disease, with a possible correlation between the presence of SRB in the oral microbiota and periodontal disease.