The antibacterial effects of coffee extract, chlorhexidine, and fluoride against Streptococcus mutans and Lactobacillus plantarum: An in vitro study

The aim of the present study was to compare the antibacterial effects of coffee extract with those of 0.2% sodium fluoride and chlorhexidine (CHX) mouthrinses on Streptococcus mutans and Lactobacillus plantarum in vitro.

In this experimental in vitro study, the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and disk diffusion method were determined for different concentrations of coffee extract, 0.2% CHX, and 0.2% fluoride against S. mutans and L. plantrum. Data were analyzed using Kruskal–Wallis analysis. Statistical significance level was established at P < 0.05.

The MIC of coffee was achieved at 62.5 and 500 mg/mL against S. mutans and L. plantarum, respectively. The MBC against S. mutans was 125 mg/mL. The diameter of the zone of inhibition around S. mutans for pure coffee extract (100%), CHX (0.2%), and fluoride was 19.8 mm, 9.92 mm, and 0, respectively. At a concentration of 6.25%–100%, coffee had a significantly larger zone of inhibition compared to CHX and fluoride) P = 0.01). The MBC of coffee and fluoride was 0 against L. plantarum. The lowest inhibitory concentration belongs to CHX (MIC: 0.624 mg/ml for L. plantarum and 0.125 mg/ml for S. mutans).

The coffee had an antibacterial effect against S. mutans on 62.5–1000 mg/ml concentrations. The zone of inhibition around S. mutans for higher concentrations of coffee (6.25%–100%) was significantly higher than that of CHX and fluoride 0.2%. Bacteriostatic effect of coffee against L. plantarum was obtained at 500–1000 mg/ml. However, coffee and fluoride did not show any bactericidal effects against L. plantarum.