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

Abstract

Objective: Dental caries is a common infectious disease. Streptococcus mutans is the prevalent
decay microorganism. The anti Streptococcus mutans activity of non fermented and
semi-fermented tea has been shown. The aim of this study was to determine the anti Streptococcus
mutans activity of Iranian green and black tea (non fermented and fermented
type).
Materials and Methods: The study was experimental. The aerial parts of wild-growing
Camellia sinensis were collected from Lahijan province. The methanolic extract of green
and 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 extracts
were tested using the well assay method. The agar dilution method recommended by the
NCCLS standards (National Committee for Clinical Laboratory Standards) was used. The
minimum inhibitory concentration (MIC) was determined as the lowest concentration of
extract inhibiting visible growth of the organism on the agar media plate. Minimum bactericidal
concentration (MBC) was detected from MIC.
Results: The Iranian green and black tea had an antibacterial effect on 100 to 400 mg/ml
concentrations. The minimum inhibitory concentration of green and black tea was 150 and
50 mg/ml, respectively. The mean diameter of inhibition zone were 9.5 mm and 10.9 mm
for methanolic extract of green and black tea, respectively.
Conclusion: Both Iranian non fermented (green tea) and fermented (black tea) have anti
Streptococcus mutans activity in vitro. The anti Streptococcus mutans activity of black tea
appears on a lower concentration than green tea.