Introduction

Tea is an infusion of flavorful leaves that has been consumed for centuries as a beverage and is valued for its medicinal properties. The phytochemcial screening of tea revealed the presence of alkaloids, saponins, tannins, catechin and polyphenols (Sofowara 1984, Opara 1992). Toda et al. (1989a) also showed that moderate daily consumption of green tea killed Staphylococcus aureus and other harmful bacteria.

Recent reports however indicate the tea's antibacterial and bactericidal properties on various bacteria strains isolated for patients with infected root canels (Horiba et al. 1991). Subsequently, several studies on the antimicrobial properties of Japanese tea have been reported (Okubo et al. 1989, Sakanaka et al. 1989, Toda et al. 1989a). The antibacterial activity of Turkish tea against Campylobacter sp and the protective activity of tea against infection by Vibrio cholerea OI have also been reported [Diker 1991, Toda et al. 1991).

Prompted by these reports, the study is aimed at investigating the antibacterial activities of extract in Kenyan and Nigerian tea bags on selected microorganisms.

Materials And Methods

Collection of sample

Tea Extraction

Test Organism

Antibacterial Susceptibility Test: Agar-gel diffusion

Results

The effect of 5,10, and 20% concentrations of the Kenyan and Nigerian lipton tea extracts on selected bacteria are presented in Table 1. it can be seen that at all three concentrations the Nigerian lipton tea extract showed inhibitory effects on Staphylococcus aureus, Vibrio cholerae 01 and Escherichia coli only. The Kenyan tea extract produced appreciable activity (zone of inhibition) against Staphylococcus aureus Vibrio cholerae 01, Escherichia coli, and Proteus sp. There was no zone of inhibtion on Salmonella sp and Pseudomonas aeruginosa (Table 1).

Figure 1

Table 1: Antibacterial activity (mean inhibition zones in mm) of Kenyan and Nigerian tea on selected organisms.

Discussion

The antibacterial effect of foreign brands of tea against Staphylococcus aureus Escherichia coli and Vibrio cholerae 01 has been reported (Toda et al. 1989a). Also antimutagenic and anti carcinogenic effect of these teas have also been documented (Komori et al. 1993, Kuroda et al. 1999). The same observation was made in this study using the Kenyan and Nigerian teas. In addition, only the Kenyan tea showed more promise by its inhibitory actions on most of the organisms tested in this study.

It was also observed that the antibacterial activity of tea extract was not demonstrated in all types of tea or in tea grown in all geographical locations for examples 20% extract of the Nigeria Lipton tea showed little or no effect on Proteus sp, but the same concentration of Kenya tea produced a mean zone of inhibition of 6.1mm. The zone of inhibition produced by Kenyan tea on test organism were generally larger than those produced with the Nigerian Lipton tea. This could be because it contains more active ingredients (phytochemical substances) than the Nigerian tea, which resulted in an inhibitory effect on the test organism.

This study has showed that the extracts in the Kenya and Nigerian tea bags have antibacterial properties against a number of bacteria. The potential utilization of these properties especially in relieving stomach cramp and weight loss is the subject of another study.