Antimicrobial Activity of Lippia adoensis var. koseret Against Human Pathogenic Bacteria and Fungi

Abstract

Background: Lippia adoensis var. koseret is a well known medicinal plant endemic to Ethiopia. It has been traditionally used to treat different infectious diseases and also in food preparation as condiment. The aim of the current study was to evaluate antibacterial and antifungal activities of water, ethanol and methanol based crude extracts of L. adoensis var. koseret against selected human pathogenic bacteria and fungi. Methods: Crude extracts of L. adoensis var. koseret were extracted by maceration method. Disc diffusion assay of the extracts were carried out in four different concentrations against three different bacteria species (Staphylococcus aureus, Enterococcus faecalis and Escherichia coli) and two clinical isolated fungal species (Candida albicans and Aspergillus flavus) by using Kirby- Baur disk diffusion method. Agar dilution method was used to determine the minimum inhibitory concentration, the minimum bactericidal and fungicidal concentrations of the extracts against similar microorganisms. Results: Water-based extract of L. adoensis var. koseret exhibited significantly less antimicrobial activity as compared to ethanol and methanol crude extract against tested isolates of bacteria and fungi (P < 0.05); while, there was no significant difference between ethanol and methanol extracts. Among the tested microorganism S. aureus, was the most sensitive of all whereas C. albicans was the most resistant microorganism to alcohol based extract of L. adoensis var. koseret. The minimum inhibitory concentration of L. adoensis var. koseret ranged from 3.12 to 25mg/ml in the alcohol based extracts but it was higher in the water-based extract. The lower bactericidal concentration (5.20 mg/l) and the highest fungicidal concentration (37.50 mg/ml) were observed in methanol based extracts against S. aureus and C. albicans, respectively. Conclusions: Antimicrobial activity of L. adoensis var. koseret varies with extraction solvent and tested microorganisms.