effect of allium sativum extract on erythromycin and methicillin resistant bacteria isolated from hospital operating room

background :   this study aimed to evaluate antibacterial effect of allium sativum, garlic extract on erythromycin and methicillin resistant bacteria isolated from an operating room in a teaching hospital in tehran, i.r. iran.   methods :   the antibacterial effect of garlic extract was investigated on 70 bacterial strains. the selected isolates were resistant to erythromycin and or methicillin, which were isolated from an operating room. antibiotic sensitivity was done using an agar well diffusion procedure and either a micro dilution method. each of the bacterial strains were exposed to concentrations of 4, 8, 12, 16, 20 and 24 µg/ml of garlic extract, separately. the growth rate of the strains was determined by measurement of the inhibition zone diameter, colony count and either by measurement of the optical density.   results :    the results showed that 70 (100%) of the strains in agar well diffusion method were sensitive to 4- 12 µg/ml of garlic extract with mic 8 µg/ml. while, the results of micro dilution method showed that 40 out of 70 strains were mic ≥ 12 µg/ml for ge.   conclusion :   the results of this study indicated that the mic and minimum bactericidal concentration of garlic extract were 8 µg/ml and 16 µg/ml, respectively. these finding indicated that garlic extract inhibit the growth of erythromycin and methicillin resistant bacterial strains.