Antibacterial Activities of Guava (Psidium guajava) Leaf Aqueous Extract Against Staphylococcus aureus and...

This study evaluated the in vitro antibacterial activity of aqueous extracts of guava (Psidium guajava) leaves against two pathogenic bacteria: Gram positive Staphylococcus aureus and Gram negative Escherichia coli. The interventional study was conducted from July 2021 to June 2022 in the Department of Pharmacology and Therapeutics in collaboration with the Department of Microbiology, Mymensingh Medical College, Bangladesh. Antibacterial activity of the aqueous guava leaf extract (AGLE) was assessed at various concentrations using disc diffusion and broth dilution methods. Gentamicin was used as a standard antibiotic control in the broth dilution test and its activity was compared with that of AGLE. The extract was initially tested at eight concentrations (25, 50, 100, 200, 400, 600, 800 and 1000 μg/mL), followed by additional selected concentrations to more precisely define the sensitivity range and determine the minimum inhibitory level. Concentrations of 800 μg/mL and above produced clear inhibitory effects against both S. aureus and E. coli. The minimum inhibitory concentration (MIC) of AGLE for both organisms was 800 μg/mL. In contrast, the MIC of gentamicin was 1.5 μg/mL for S. aureus and 1 μg/mL for E. coli, indicating a substantially stronger antibacterial effect of gentamicin compared to AGLE under the same experimental conditions. Overall, the findings demonstrate that aqueous guava leaf extract possesses measurable antibacterial activity against S. aureus and E. coli, although its potency is lower than that of Gentamicin and suggest that guava leaves may serve as a potential complementary source of antimicrobial agents' in future antimicrobial drug research and development.