Objective: This study was conducted to estimate oral colonization by Streptococcus mutans and Streptococcus sanguinis in adults with high and without any caries experience. Furthermore, differences in the amount of hydrogen peroxide (H2O2) produced by S. sanguinis isolated from both groups were assessed.
Design: Forty adults were divided into: (i) carious lesion-free, without any carious lesion, assessed by the International Caries Detection and Assessment System (ICDAS), or restoration, (CF) and (ii) high caries experience (HC). Saliva samples were collected and seeded on respective agar-plates for enumeration of total streptococci, S. mutans and S. sanguinis (CFU/mL) and compared between groups. Additionally, S. sanguinis colonies obtained from both groups were inoculated on Prussian blue agar for H2O2 detection. Production of H2O2 was quantified and compared between the two groups. S. sanguinis counts were significantly higher in CF than HC individuals (p<0.05). Conversely, S. mutans showed significantly higher levels in HC than CF subjects (p<0.001). S. sanguinis colonies from CF individuals produced significantly larger H2O2 halos compared with HC subjects.
Conclusions: S. sanguinis predominates over S. mutans in saliva of adults without caries experience. In those people, S. sanguinis produces more H2O2ex vivo.
Keywords: Bacterial competition; Bacterial interaction; Dental caries; Oral biofilm; Streptococcus mutans; Streptococcus sanguinis.
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