In vitro antimicrobial activity of propolis and synergism between propolis and antimicrobial drugs

Area of Science:

• Pharmacology
• Microbiology
• Natural Products Chemistry

Background:

• Antibiotic resistance is a growing global health concern.
• Natural products like propolis offer potential alternative antimicrobial strategies.
• Propolis, a bee product, is known for its diverse biological activities.

Purpose of the Study:

• To evaluate the antimicrobial properties of Serbian ethanolic propolis extract (EEP) against a broad spectrum of microorganisms.
• To assess the synergistic effects of EEP in combination with conventional antimicrobial drugs.
• To identify the susceptibility profiles of resistant bacterial and yeast strains to EEP.

Main Methods:

• Agar diffusion and agar dilution methods were employed to determine minimum inhibitory concentrations (MICs).
• Synergistic activity was evaluated using the disc diffusion method on agar with subinhibitory EEP concentrations.
• Thirty-nine microbial strains, including 14 antibiotic-resistant ones, were tested.

Main Results:

• EEP exhibited significant antimicrobial activity against Gram-positive bacteria (MIC 0.078%-1.25%) and yeasts (0.16%-1.25%).
• Gram-negative bacteria showed lower susceptibility (1.25%-5%), with Salmonella spp. being the most resistant.
• Enterococcus faecalis and Candida albicans were the most resistant Gram-positive bacterium and yeast, respectively.
• EEP demonstrated synergistic effects with selected antibiotics and enhanced antifungal activities.

Conclusions:

• Ethanolic propolis extract possesses broad-spectrum antimicrobial potential against various microorganisms, including resistant strains.
• Propolis can potentiate the activity of existing antibiotics and antifungals, suggesting a role in combination therapies.
• These findings highlight the potential medical applications of propolis in combating microbial infections, especially those involving resistant pathogens.