Synergetic Effects Of Plant Extracts And Antibiotics On Staphylococcus Aureus Strains Isolated From Clinical Specimens

This research focuses on antimicrobial activity of different water plant extracts: Psidium guajava, Rosmarinus officinalis, Salvia fruticosa, Majorana syriaca, Ocimum basilucum, Syzygium aromaticum, Laurus nobilis, and Rosa damascena alone and then synergy testing of these extracts with known antimicrobial agents of different mechanisms (protein synthesis inhibition: oxytetracycline HCl and gentamicin sulfate; cell wall synthesis inhibition: penicillin G and cephalexin; folic acid synthesis inhibition: Sulfadimethoxine as sodium; and nucleic acid synthesis inhibition: enrofloxacin) using both well-diffusion and microdilution method. The results of the conducted experiments using well-diffusion method demonstrated that these plants extracts contain bioactive compounds some of which has a weak effect. In vitro interactions between the above mentioned antibiotics and plant extracts using the previous method were mainly additive against the four strains of S. aureus. While in vitro study using microdilution method showed synergistic effects with significant reduction in the MICs of the test antibiotics, resulting from the combination of antibiotics with different crude plant extracts against 3 strains of S. aureus. The change in MIC was noticed in all plant extracts against test antibiotics including these plants showed weak antibacterial activity by well diffusion method. Also our results showed that synergism effects between antimicrobial agents and plant extracts were occurred in both sensitive and resistant strains but the magnitude of minimum fold inhibition in resistant strains was higher than the sensitive strains.