Nader Kazemi - Assistant Professor, Nanobiotechnology Research Center, Zanjan Branch, Islamic Azad University, Zanjan, Iran
Mahdi Arfaei - BSc student of Microbiology, Department of Biology, Faculty of Basic Sciences, Zanjan Branch, Islamic Azad University, Zanjan, Iran.

BACKGROUND AND ABJECTIVEInfectious diseases are one of the most common diseases around the world which impose enormous financial burden on society. Staphylococcus aureus is an important cause of nosocomial infections and multidrug resistance. Although synthetic antibiotics have been able to play an important role in treatment of infectious diseases in past decades, however problems related to microbial resistance of antibiotics have caused that the medical plants to be considered as an alternative.MATERIALS AND METHODSEthanolic and acetonic extracts were prepared from dried leaves of the Lavandula angustifolia and Rosmarinus officinalis, then anti-bacterial activities of the extracts for Staphylococcus aureus were experimented, first by the method of well diffusion in agar, and later the amount of the MIC and MBC of the extracts were measured by broth microdilution method. In animal model, first ۵×۱۰۵ CFU/ml of bacteria was intraperitoneally injected and after ۲۴ hours, ۰.۵ml (as MBC concentration of each the extracts) of extracts, to female BALB/c mice was intraperitoneally injected. Then, the counting of bacterial colonies in spleen were determined with cultivation on Mueller Hinton agar after ۷ days as the standard protocol.RESULTS AND DISCUSSIONThe experiment results concerning the determination of growth inhibition diameter in agar showed that the maximum of growth inhibition diameter is related to the acetonic extract of Lavandula angustifolia (۲۰ mm), and the minimum of growth inhibition diameter is related to ethanolic extract of Rosmarinus officinalis (۱۰ mm) at the highest concentration (۴۰۰ mg/ml). In conditions of in vivo, after ۴۸ hours spleen supernatant cultivation, the average number of bacteria for acetonic extracts of the Lavandula angustifolia and Rosmarinus officinalis were ۱.۸×۱۰۳ CFU/ml and ۶.۶×۱۰۳ CFU/ml respectively and for ethanolic extracts of Lavandula angustifolia and Rosmarinus officinalis were ۱۰.۸×۱۰۳ CFU/ml and۱۴.۶×۱۰۳ CFU/ml respectively. These results showed significantly decrease in number of bacteria in all experimental groups (p˂۰.۵) compared to control group.CONCLUSIONIn general, the results of evaluations in experimental conditions and the animal model showed that acetonic and ethanolic extracts of these plants have the effective antibacterial activity against mentioned bacteria and can be useful to treatment of nosocomial infections.

Antimicrobial, Lavandula angustifolia, Rosmarinus officinalis, Staphylococcus aureus.