In vitro Antimicrobial Activities of Methanol Crude Leaf Extract of Psidium guajava L. on Clinical Isolates of Multidrug Resistant Staphylococcus aureus

This study looks at the chemical makeup and antibacterial activity of a methanol crude leaf extract of Psidium guajava Linn against clinical isolates of Staphylococcus aureus from FMC Umuahia, Abia State, that are resistant to multiple drugs. For further antibacterial testing, we chose strains that showed resistance to every antibiotic we tried. Inhibitory concentrations (MICs) of methanol and water extracts were determined to be 625 ug/ml and 7.5 mg/ml, respectively. The MBC for methanol extracts was 1.25 mg/ml, whereas the MBC for aqueous extracts was 12.5 mg/ml. The maximum bactericidal concentration of methanol extract was found to suppress the development of the MDR strain by 85%. Results from a time-kill study showed that mat methanol extract (5 mg/ml) was effective against MDR bacteria within 10 hours. The extract showed potent protein degradative activity when tested on the total polypeptide profiles of bacterial cultures using SDS-PAGE. Last but not least, a human red blood cell (RBC)-based hemolytic test demonstrated no hemolysis at doses greater than MBC, supporting its safety for therapeutic application.