In-vitro antibacterial activity of selected medicinal plants from Longisa region of Bomet district, Kenya

Background: Current strategies to overcome the global problem of antimicrobial resistance include research in finding new and innovative antimicrobials from plants. This study was carried out to determine the antibacterial activity of plant extracts of Olea africana stem-bark, Psidium guajava leaves, Vernonia amygdalina leaves, Lantana camara leaves and Mangifera indica leaves which are used in folklore medicine to treat infections of microbial origin in Longisa region of Bomet District, Kenya. Methods: Methanol extracts were derived and screened. Standard cultures of Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Staphylococcus aureus ATCC 25923 were used in the study. The antibacterial tests used were the agar well diffusion assays at concentration 1gm/ml. Minimum Inhibition Concentration (MIC) was determined in the plant extract that showed some efficacy against the tested microorganisms. Gentamicin (10µg) was used as a positive control. Results: The methanol extracts showed weak antibacterial activity against the study organisms compared to Gentamicin. All extracts exhibited a significant bactericidal activity against S. aureus while L. camara and V. amygdalina lacked efficacy against P.aeruginosa and E.coli. O.africana and P. guajava presented the lowest MIC against S.aureus (62.5 mg/ml and 250 mg/ml respectively P.guajava and M. indica showed analogous MICs against P.aeruginosa (250 mg/ml). P.guajava exhibited a better MIC against E.coli (500 mg/ml). Conclusions: This in-vitro study corroborated the antimicrobial activity of the selected plants used in folklore medicine. The plants could be potential sources of new antimicrobial agent