Anti-staphylococcal activity of rosemary extract

The infection caused by Staphylococcus spp. and resistance against commonly used antibiotics is common in clinical practice. The use of creams, soaps, gels with antimicrobials could decrease level of contamination of the skin or mucous membranes. The aim of this work was to check sensitivity of staphylococci using rosemary extract. We have used more than 100 freshly isolated strains of staphylococci belonging to three main species: Staphylococcus aureus, S. epidermidis, and S. saprophyticus (some of them were MRSA positive and multiple-antibiotics resistant strains). Rosemary extract was prepared from air-dried leaves (Rosmarini folium) collected in Dalmatian (Croatian coast), and extracted with 60% (V/V) ethanol. Hole-plate diffusion antibacterial assay was performed with 50µL of alcoholic rosemary extract in concentration range from 10 to 60mg/mL. Ethanol and standard antibiotics were used as control. All investigated staphylococcal strains were sensitive to rosemary extract at 10mg/mL with inhibition zones of growth between 15 and 17mm. Higher concentration of rosemary extract (from 20 to 60mg/mL) exhibited higher inhibition zones of growth, and correlation between concentration of rosemary extract and inhibition zones was found. Inhibition zones of rosemary extracts were found bigger or equal to standard antibiotics at 10µg/mL (β-lactams, macrolides and glycopeptides). Equal sensitivity of staphylococcal species (MRSA and multiple-resistant) gives a possibility to use rosemary extract in topical preparations. Differences in antimicrobial activity between staphylococcal species and strains as well as between resistant profiles were not found, indicating uniform anti-staphylococcal activity of ethanol rosemary extract.