Abstract

This study aimed at determining the effects of the selected medicinal plants (Tagetes minuta, Aloe secundiflora, Vernonia lasiopus, and Bulbine frutescens) extracts against Clinical isolate of Shigella flexineri. Shigella flexineri is a gram-negative bacterium that is associated with gastrointestinal disturbances leading to diarrhoea in human beings. The antibacterial activity of the medicinal plant extracts against Shigella flexineri was determined using the Kirby Bauer method. The extracts showed antimicrobial activity against Shigella flexineri with Bulbine frutescens extract (minimum inhibitory concentration 3.2 μg/ml; maximum bactericidal concentration 6.2 μg/ml) being the most active when compared to the others. Tagetes minuta (minimum inhibitory concentration 7.4 μg/ml; maximum bactericidal concentration 12.6 μg/ml) extract was less active when compared to the other extracts. Bulbine frutescens had the largest average zone of inhibition 19.50 ± 1.05 mm while Vernonia lasiopus and Aloe secundiflora had the least zone of inhibition of 18.17 ± 1.47mm both. Ciprofloxacin (5μg/ml) was used as a positive control producing an average zone of inhibition of 22 ± 1.84mm while negative controls (water and dimethyl sulphoxide) showed no zone of inhibition. The preliminary qualitative screening for phytochemical showed the presence; of saponins, tannins, alkaloids, and flavonoids. The study provides insight into the antibacterial activity of the medicinal plant extracts and if they can be used in the treatment of infections caused by Shigella flexineri as an antibacterial agent.

Keywords: Shigella flexineri; Phytochemicals; Kirby Bauer; Medicinal plants; Zone of inhibition