Activity of compounds extracted from Salvia aurea against methicillin-resistant Staphylococci

Methicillin-resistant Staphylococcus aureus (MRSA) and S.epidermidis (MRSE) are Gram positive pathogens that represent a leading cause of serious human diseases worldwide and are responsible for substantial morbidity and mortality, both within the healthcare system and in the community [1,2]. We describe here the activity of three compounds, 12 methoxy-carnosic acid (MCA), 7-methoxy-rosmanol (MR) and rosmanol (R), derived from S.aurea, on 5 clinical S.aureus strains (2 MRSA and 3 MSSA) and 5 S.epidermidis strains (3 MRSE and 2 MSSE). The three molecules, identified by IR and NMR analysis, were obtained from the surface exudates by rinsing the fresh aerial part plant material with CH2Cl2 and repeated column chromatography on Sephadex LH-20 and silica gel. Table 1 shows the minimal inhibitory concentrations (MICs) of the compounds, determined by standard methods [3]. Killing curve assays, at 4 x MIC concentrations, were performed on S.aureus and S.epidermidis according to recommended procedures [3]. A description of the activity expressed on a representative MRSA and MRSE strain is shown in Fig 1 and Fig 2. MC and R displayed a clear bacteriostatic effect while MR possessed a bactericidal activity on the same pathogen. On S.epidermidis all tree compounds manifested a bacteriostatic effect. [31]Our results indicate that MCA, MR and R isolated from S.aurea represent molecules capable of inhibiting or killing methicillin-resistant Staphylococci. Investigation on their mechanisms of action are highly warranted.[1] Mandell, Douglas and Bennett (2005) Principles and Practice of Infectious Diseases, 5th ed.; Mandell, G.,Bennett, J.; Dolin, R., Eds.; Churchill Livingstone: Philadelphia; pp 2147− 2152 and 2069− 2089 [2] Witte W, Cuny C, Klare I, Nübel U, Strommenger B., Werner G (2008) Emergence and spread of antibiotic-resistant Gram-positive bacterial pathogens. Int J Med Microbiol. Jul;298(5-6):365-77. [3] Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing; sixteenth informational supplement. Document M100-S16. Wayne, PA: CLSI; 2006.