Cortisol enhances the biofilm formation of Streptococcus mutans

Cortisol, a hormone produced by adrenal cortex and released in response to psychological stress, is found in different body fluids, such as serum and saliva. Some studies indicate that stress can modify the potential of virulence of bacterial infections including caries and periodontal diseases.

Objectives: To evaluate the effect of cortisol on the biofilm formation and acid production of Streptococcus mutans (UA159).

Methods: Biofilms of S. mutans were formed (37°C - 5% CO2) on hydroxyapatite discs for 5 days (120 hours). The medium, containing 100 µM of cortisol (test group - Group A), NaCl – 0,9%(control group - Group B) or ethanol (vehicle control group - Group C), was replaced twice a day. After the experimental period (5 days), the non-adherent bacteria were removed and the adherent S. mutans were dispersed by sonication. The suspensions were plated on BHI agar and incubated for 48h (37°C - 5% CO2). After incubation, the CFU/mL were counted. In addition, the medium pH was evaluated at every medium change.

Results: Cortisol significantly increased (p<0.05 - ANOVA, Tukey) the biofilm formation on hydroxyapatite discs compared to control groups. However, the medium pH was not affected by cortisol (p>0.05 - ANOVA).

Conclusions: The findings of the present study demonstrated that cortisol can enhance the biofilm formation of S. mutans in vitro suggesting that this hormone can act as an additional risk factor to the development of caries (FAPESP # 2009/16324-4).