Abstract

The antimicrobial activities of the water and methanolic extracts of Psidium guajavaLinn. stem bark were evaluated against eight methicillin-resistant Staphylococcus aureus (MRSA) isolates. The plant material was extracted and phytochemical analyses were performed by standard procedures. The agar diffusion method was employed for the assessment of the sensitivity of the extracts, while the agar dilution technique was employed for the quantitative determination of the bacteriostatic and bacteriocidal activities of the plant extracts. The phytochemical studies of P. guajavarevealed the presence of carbohydrates, glycosides, tannins, and proteins as its major constituents. Results show that the methanolic and water extracts of P. guajava stem bark exhibited antibacterial activity against methicillin resistant S. aureus bacteria. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the stem bark water extracts ranged from 125 to 500 µg/ml while that of the stem bark methanol extract ranged from 62.5 to 250 µg/ml.

Key words: Psidium guajava, antimicrobial activity, phytochemical screening, methillin-resistant staphylococcus aureus