In vitro antibacterial activity of Psidium guajava (guava) extracts against MRSA and MSSA

Background: Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) are significant pathogens responsible for a range of infections, including those in diabetic patients. The increasing resistance to antibiotics necessitates the exploration of alternative antibacterial agents. The Psidium guajava (guava) plant has demonstrated antimicrobial properties, but its efficacy against S. aureus strains remains underexplored. Aim: To evaluate the in vitro antibacterial activity of ethanol and water extracts of guava leaf extracts against MRSA and MSSA. Setting: In vitro study conducted under controlled laboratory settings at Mangosuthu University of Technology, Department of Biomedical Sciences, Kwa-Zulu Natal, South Africa. Methods: Guava leaf extracts were prepared using ethanol and water. Antibacterial activity was assessed using the Kirby-Bauer disc diffusion method and minimum inhibitory concentration (MIC) assays. The zone of inhibition size and MIC values were measured for both MRSA and MSSA. Results: The water-based extract produced larger zones of inhibition and lower MIC values compared to the ethanol extract, indicating higher potency. However, both extracts showed reduced activity against MRSA, which may be attributed to the presence of the mecA gene, conferring resistance to β-lactam antibiotics. Conclusion: While the water-based guava extract demonstrated significant antibacterial potential against both MRSA and MSSA, further research is needed to isolate specific bioactive compounds and assess clinical applicability. Contribution: These findings suggest that guava leaves may offer a natural alternative or adjunctive treatment for S. aureus infections, including those caused by antibiotic-resistant strains.