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

Najmeh Akhlaghi, Marziye Sadeghi, Fataneh Fazeli, Shiva Akhlaghi, Maryam Mehnati, Masuod Sadeghi


Background: 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.
Materials and Methods: 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.
Results: 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).
Conclusion: 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.
Key Words: Chlorhexidine, coffee, sodium fluoride, Streptococcus mutans

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