Antimicrobial effect of ursolic acid and oleanolic acid against methicillin-resistant staphylococcus aureus

Abstract

The antimicrobial activity of ursolic acid (UA) and oleanolic acid (OA), both triterpenoid compounds, against methicillin-resistant Staphylococcus aureus (MRSA) is controversial. We examined the antimicrobial effects of UA and OA against 19 strains of MRSA isolated from Koreans by determining minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC). The data showed that the methicillin-sensitive strain S. aureus KCTC 1621T was more resistant to UA and OA than that of the MRSA strains. The MBC values of UA and OA against MRSA had broad ranges; 4 to 32 μg/ml and 16 to >256 μg/ml, respectively. It was difficult to understand the different antimicrobial activities of UA and OA among the MRSA strains, because UA and OA antimicrobial mechanisms are unknown. These results indicate that the antimicrobial effects of UA and OA against MRSA are dependent on resistance to UA and OA in each strain. © 2012, The Microbiological Society of Korea.