Abstract
Background:
Antibiotic resistant pathogens became a real global threat for human and animal health. This needs to concentrate the efforts to minimise and control these organisms. Efflux pumps are considered as one of the important strategies used by bacteria to exclude the harm materials out of the cell. Inhibition of these pumps can be an active strategy against multidrug resistance (MDR) pathogens. There are two source of efflux pump inhibitors can be used, chemical and natural inhibitors. The chemical origin efflux pump inhibitors have many toxic side effects while the natural origin characterized by a wide margin of safety for the host cell.
Aim:
In this study the ability of some plant extracts like (propolis show rosemary, clove, capsaicin and cumin) to potentiate the inhibitory activity of some antibiotics as (ciprofloxacin, erythromycin, gentamycin, tetracycline and ampicillin) against S. aureus pathogen were tested.
Methods:
Efflux pump inhibitory activity of the selected plant extracts were tested using ethidium bromide accumulation assay.
Results:
The results have shown that Propolis has a significant synergistic effect in combination with ciprofloxacin, erythromycin and gentamycin. While, it has no effect with tetracycline or ampicillin. Also, no synergic effect was noticed in combination of the MIC for the selected plant extracts (rosemary, clove, capsaicin and cumin) with any of the tested antibiotics. Interestingly, according to the results of EtBr accumulation assay, Propolis has potent inhibitory activity against S. aureus (MRS usa300) pump system.
Conclusion:
This study suggests that Propolis might act as a resistance breaker that is able to restore the activity of ciprofloxacin, erythromycin and gentamycin against S. aureus strains, in case of the Efflux-mediated antimicrobial resistance mechanisms.

Key words: Antibiotic resistance, Efflux pump inhibitors, Plant extracts, S. aureus