Antibacterial Activity of Iranian Green and Black Tea on Streptococcus Mutans : An In Vitro Study

Objective: Dental caries is a common infectious disease. Streptococcus mutans is the prevalentdecay microorganism. The anti Streptococcus mutans activity of non fermented andsemi-fermented tea has been shown. The aim of this study was to determine the anti Streptococcusmutans activity of Iranian green and black tea (non fermented and fermentedtype).Materials and Methods: The study was experimental. The aerial parts of wild-growingCamellia sinensis were collected from Lahijan province. The methanolic extract of greenand black tea were examined on Streptococcus mutans (ATCC3566). Five different concentrations(50mg/ml, 100mg/ml, 200mg/ml, 300mg/ml and 400 mg/ml) of tea extractswere tested using the well assay method. The agar dilution method recommended by theNCCLS standards (National Committee for Clinical Laboratory Standards) was used. Theminimum inhibitory concentration (MIC) was determined as the lowest concentration ofextract inhibiting visible growth of the organism on the agar media plate. Minimum bactericidalconcentration (MBC) was detected from MIC.Results: The Iranian green and black tea had an antibacterial effect on 100 to 400 mg/mlconcentrations. The minimum inhibitory concentration of green and black tea was 150 and50 mg/ml, respectively. The mean diameter of inhibition zone were 9.5 mm and 10.9 mmfor methanolic extract of green and black tea, respectively.Conclusion: Both Iranian non fermented (green tea) and fermented (black tea) have antiStreptococcus mutans activity in vitro. The anti Streptococcus mutans activity of black teaappears on a lower concentration than green tea.