Date of Completion

2025

Document Type

Thesis

Degree Name

Bachelor of Science in Pharmacy

Keywords

AMR, MRSA, Muntingia calabura, Vancomycin, TFC, TPC, MIC, Checkerboard, FIC Index, Synergism

Abstract

Antimicrobial resistance (AMR) poses a crucial threat to global public health, with methicillin-resistant Staphylococcus aureus (MRSA) being one of the most formidable challenges due to its resistance to multiple antibiotics and its association with increased morbidity, mortality, and healthcare costs. In the Philippines alone, MRSA remains highly prevalent, with resistance rates exceeding 50% in recent years, prompting the need for adjunctive and alternative treatment strategies. Natural products offer a favorable avenue for antimicrobial therapies. Muntingia calabura (aratiles) has a well-established history, and its leaves are known to contain bioactive compounds that may contribute to its antimicrobial effect. This study investigates the antibacterial activity and potential synergistic effects of the Muntingia calabura ethanolic leaf extracts (MCELE) in combination with vancomycin against MRSA. Results show that the MCELE contained significant levels of phenolics and flavonoids, 6.072 mg GAE/g of MCELE and 0.2488 (QE)/g of MCELE, respectively. The MCELE demonstrated inhibitory effects against MRSA at a Minimum Inhibitory Concentration (MIC) of 2000 mcg/mL with a %BGR of 95.47%. Vancomycin alone had a %BGR of 97.627% at an MIC of 1 mcg/mL, confirming MRSA’s susceptibility to vancomycin according to the CLSI guidelines (MIC < 2 mcg/mL). Moreover, the combination of 1000 mcg/mL MCELE and 0.25 mcg/mL Vancomycin exhibited a synergistic effect, with a fractional inhibitory concentration (FIC) index of 0.375, falling within the synergy range of ≤ 0.5. The FIC index values confirmed the synergy, suggesting that combining MCELE with vancomycin could lower the effective dose of vancomycin required to inhibit MRSA. The findings support the potential of MCELE as an effective adjunct to vancomycin therapy against MRSA. The observed synergy between MCELE and vancomycin highlights a promising strategy to enhance antibacterial efficacy and potentially mitigate the development of further resistance.

First Advisor

James S. Dayrit, RPh

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