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Comparative Dose-Dependent Antibacterial Effects of Natural Substances and Conventional Antibiotics

CSEF · 2026 Microbiology (Junior Division)

Eylul Sahin

Overview

The increasing concern surrounding antibiotic resistance has brought interest in alternative or complementary antimicrobial agents. This study investigated the antibacterial effects of selected natural substances such as garlic, ginger, oregano, and Manuka honey in comparison with the antibiotic gentamicin against Escherichia coli K-12. These natural substances were selected due to being displayed as natural antibacterial agents to the public eye for years. Bacterial cultures were exposed to designated concentrations of each substance. Bacterial growth was measured using optical density measurements at 600 nm and supported by visual agar plate diffusions with disk diffusion and well diffusion methods on agar plates. Gentamicin showed nearly complete inhibition of bacterial growth compared to the positive control on all tested concentrations. Among the natural substances, garlic and Manuka honey demonstrated strong dose dependent antibacterial activity, while oregano and ginger showed limited or inconsistent effects. My findings suggest that certain natural compounds may have potential as complementary antimicrobial agents under scientific methods.

Competition history

  • CSEF 2026 Microbiology (Junior Division) · Entry J-16-15

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