Synergistic Antibacterial Activity of Argyranthemum foeniculaceum Extract with Antibiotics on Bacteria Causing Periodontal Diseases

Background: Argyranthemum foeniculaceum is a traditional herb used in Yemeni folk medicine to treat mouth infections. Phytochemical acetylenes and sesquiterpene lactones were isolated from this plant. A. foeniculaceum possesses antibacterial activity, but there is no current data on its activity alone or combined with antibiotics against bacteria causing periodontal diseases. Objective: This study aimed to evaluate the antibacterial activity of ethanol extract of A. foeniculaceum and antibiotics (ampicillin, gentamicin and levofloxacin) as well as their combination against S. aureus, S. mutans, S. pyogenes, and A. actinomycetemcomitans. Materials and Methods: The antibacterial activities of ethanol extract and antibiotics were evaluated using the agar-well diffusion method. The minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of plant extract against selected bacteria were assessed using the microdilution method. The synergistic effect of plant extract in combination with antibiotics was evaluated by measuring the diameter of the zone of inhibition. Results: In this study, ethanol extract of A. foeniculaceum showed good antibacterial activity against four bacteria that cause periodontal diseases. The Maximum antibacterial effect was exhibited by A. foeniculaceum extract against A. actinomycetemcomitans (MIC = 6.25 µg/ml, and MBC = 12.5 µg/ml), whereas the minimum activity was displayed by A. foeniculaceum extract against S. aureus (MIC = 50 µg/ml and MBC = 50 µg/ml). The interactions between A. foeniculaceum crude extract and the antibiotics used varied, with synergistic, additive, and antagonistic effects observed depending on the bacteria strain. The best synergism was displayed by the plant extract with gentamicin against A. actinomycetemcomitans (the inhibition zone was 33 mm). Combinations of Levofloxacin and ethanol extract showed an additive action against A. actinomycetemcomitans Conclusion: A. foeniculaceum extract can be used alone or in combination with antibiotics in the fight against bacterial infections that cause periodontal disease.