Abstract:The emergence of antibiotic-resistant microorganisms, particularly Escherichia coli, underscores the need for alternative infection control strategies. This study investigated the antibacterial activity of oregano (Plectranthus amboinicus) and lemongrass (Cymbopogon citratus), both rich in phenols and flavonoids with antimicrobial properties. Macrobroth Dilution Susceptibility Testing determined the MIC and MBC, with interactions assessed using the FIC Index. The study hypothesized enhanced antimicrobial activity through synergistic effects. However, statistical analyses showed that the MIC data were not normally distributed (p < 0.001) and homogeneity of variances was violated (p < 0.001). Treatment type significantly influenced MIC (p = 0.00108), while concentration and treatment-concentration interactions did not (p > 0.05). Post-hoc tests showed significant differences between bleach and both extracts (p = 0.0092 and p = 0.0215), but no significant difference between lemongrass and oregano (p = 0.6028). Results indicated additive rather than synergistic effects, with bleach achieving bactericidal activity. While the combination effectively inhibited bacterial growth, it cannot replace bleach for complete eradication, though it shows promise as a natural disinfectant in less critical settings.
Keywords: Antimicrobial Resistance (AMR), Antibiotic resistance, Escherichia coli, oregano, lemongrass, natural antimicrobials, MIC, MBC, FIC Index, synergistic effect, additive effect
