Screening of Chinese medicinal plants for inhibition against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA)

Ethnopharmacological relevanceTraditional herbs are a valuable source of novel antibacterials in combating pathogenic isolates of methicillin-resistant Staphylococcus aureus (MRSA), a global nosocomial problem.Aim of the studyTo assess in vitro anti-MRSA activity of extracts from Chinese herbs. The minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) were determined in the setting of clinical MRSA isolates.Materials and methodsA collection of 19 plant extracts were obtained and bioassay-guided phytochemical analysis performed. Antibacterial susceptibilities were screened for inhibitory zone and MICs/MBCs determined by serial dilution with a standardized microdilution broth methodology. 9 MRSA isolates and a standard control strain (ATCC 25923) were cultured and exposed to the plant extract and isolated compound. Vancomycin was used as a positive control agent.ResultsAll the presented 19 plants showed anti-MRSA activity with MIC of 1.25–3.07 mg/ml. The most active antimicrobial plants were Dendrobenthamia capitata, Elsholtzia rugulosa, Elsholtzia blanda, Geranium strictipes and Polygonum multiflorum (MIC ≤ 1.43 mg/ml), and betulinic acid isolated from the active ethyl acetate fraction of Dendrobenthamia capitata extract was determined with MIC/MBC values as 62.5/125.0 mg/ml.ConclusionsDendrobenthamia capitata, Elsholtzia rugulosa, Elsholtzia blanda, Geranium strictipesPolygonum multiflorum and betulinic acid demonstrate promising anti-MRSA potential.