AB107. Synergistic antimicrobial potential of lemongrass and Cuban oregano: a comparative evaluation of efficacy for potential disinfectant use
Abstract

AB107. Synergistic antimicrobial potential of lemongrass and Cuban oregano: a comparative evaluation of efficacy for potential disinfectant use

Jesela Angeli R. Agas1, Rafael Miguel C. Alibarbar1, Darylle Marie Hannah M. Ang1, Sebastian Angelo B. Balmes1, Antoinette Dominique M. Bautista1, Erin Dominique M. Buenaventura1, Mark Kevin P. Devanadera2, Vivian Villegas1, Maria Luisa R. Olano1

1Department of Medical Technology, University of Santo Tomas, Manila, Philippines; 2Department of Biochemistry, University of Santo Tomas, Manila, Philippines

Background: 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.

Methods: Macrobroth dilution susceptibility testing was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the samples. To evaluate the interaction between the antimicrobial agents, the fractional inhibitory concentration (FIC) index was calculated. This approach allowed the assessment of whether the combined agents exhibited synergistic, additive, or antagonistic effects. The study specifically hypothesized that combining the agents would enhance antimicrobial activity through synergistic interactions, resulting in improved inhibition and bacterial killing compared to the effects of each agent used alone.

Results: However, statistical analyses showed that the MIC data were not normally distributed (P<0.001) and that the assumption of homogeneity of variances was violated (P<0.001). Treatment type significantly influenced MIC (P=0.001), whereas concentration (P>0.05) and the treatment–concentration interaction (P>0.05) did not show significant effects. Post hoc comparisons revealed significant differences between bleach and lemongrass extract (P=0.009) as well as between bleach and oregano extract (P=0.02), while no significant difference was observed between lemongrass and oregano extracts (P=0.60). Overall, the results indicated additive rather than synergistic effects, with bleach demonstrating bactericidal activity.

Conclusions: Although the combination was effective in inhibiting bacterial growth, it cannot fully replace bleach for complete microbial eradication. However, the results indicate its potential as a natural disinfectant, particularly for use in less critical or low-risk settings where harsh chemical disinfectants are not required.

Keywords: Escherichia coli; fractional inhibitory concentration index (FIC index); lemongrass; natural antimicrobials; oregano

Footnote

Conflicts of Interest: The authors have no conflicts of interest to declare.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the noncommercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

doi: 10.21037/jphe-26-ab107
Cite this abstract as: Agas JAR, Alibarbar RMC, Ang DMHM, Balmes SAB, Bautista ADM, Buenaventura EDM, Devanadera MKP, Villegas V, Olano MLR. AB107. Synergistic antimicrobial potential of lemongrass and Cuban oregano: a comparative evaluation of efficacy for potential disinfectant use. J Public Health Emerg 2026;10:AB107.

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