Antimicrobial activity of tanzanian chewing sticks against oral pathogenic microbes

Methanol extracts from the bark and wood of ten plants used as chewing sticks in Morogoro region, in Tanzania, were tested for their ability to inhibit the growth of cariogenic bacteria, Streptococcus mutans , Actinomyces viscosus and a yeast Candida albicans . Screening for antimicrobial activity was done by the agar-hole diffusion method, and minimum inhibitory concentrations (MICs) were determined by the agar dilution method. Extracts from seven out of the ten plants showed varying degrees of growth inhibitory effect on the microorganisms, with Acacia senegal var. senegal stem bark being the most active, followed by the stem bark of Eriosema psoraleoides . Their MICs ranged from 0.63 mg/ml to 5 mg/ml. Three plants Ocimum suave , Opilia celtidifolia and Xerophyta suaveolens did not exhibit any antimicrobial effect. Actinomyces viscosus was relatively more sensitive to the extracts than S. mutans and C. albicans . This study has also demonstrated that most bark extracts possessed antimicrobial activity, while many wood extracts were inactive. It is, therefore, advisable to use, for toothbrushing, unpeeled, rather than peeled chewing sticks, in order to exploit fully their antimicrobial effect. However, additional studies are needed to determine their antiplaque, anticaries and antimycotic effects.