Synergistic effect of Thymbra spicata L. extracts with antibiotics against multidrug- resistant Staphylococcus aureus and Klebsiella pneumoniae strains

Abstract

<strong><em>Objective(s)</em></strong>: To evaluate the <em>i</em><em>n vitro</em> interaction between different extracts of <em>Thymbra spicata </em>L. and certain antimicrobial drugs of different mechanisms, including ampicillin, cefotaxime, amikacin and ciprofloxacin. This study was performed against multidrug-resistant strains of <em>Staphylococcus aureus</em> and <em>Klebsiella</em> <em>pneumoniae.</em> <strong><em>Materials and Methods: </em></strong>Evaluation of antibacterial activity and synergy interaction between plant extracts and antimicrobial agents was carried out using checkerboard microdilution. <strong><em>Results:</em></strong> Different interactions (synergistic, additive and indifference) were observed between plant crude extracts and used antibiotics depending on the strain. The fractional inhibitory concentration (FIC) index ranged from 0.02 to 1.5 for <em>S. aureus</em> and 0.25 to 2 for <em>K. pneumoniae</em> strains. The best synergistic capacity appeared with cefotaxime against <em>S. aureus</em> strains, where the activity of cefotaxime was increased from 8- to 128-fold. <strong><em>Conclusion:</em></strong> These results may indicate that <em>T. spicata</em> extracts potentiates the antimicrobial action of antibiotics, suggesting a possible utilization of this herb in combination therapy against emerging multidrug-resistance <em>S. aureus</em> and <em>K. pneumoniae</em><em>.</em>