title: Studies on antimicrobial activity of Poncirus trifoliata ethyl extract fraction against methicillin-resistant Staphylococcus aureus and to elucidate its antibacterial mechanism.
abstract: Traditional medicinal plants contain a wide variety of chemicals that have potent antibacterial activity. To find an alternative agent of overcoming the problems of methicillin-resistant Staphylococcus aureus (MRSA), the antibacterial mechanism of Ponciruss trifoliata against MRSA was investigated. Ethyl acetate (EtOAc)-soluble extract of P. trifoliata methanolic extract was evaluated for antibacterial activity using minimum inhibitory concentration (MIC). An EtOAc sub-fraction 08 (EA08) from silica-gel open column chromatography exhibited strong anti-MRSA activity. Apart from the study to isolate single compound from EA08, a synergistic antibacterial effect between the sub-fraction and β-lactam antibiotics against MRSA was determined. In order to elucidate the antibacterial restoring mechanism of EA08 on MRSA, mRNA expression of mecA gene and production penicillin-binding protein 2a (PBP2a) encoded by mecA gene were monitored. EA 08 showed the strongest antibacterial activity with MIC value of 256 μg ml(-1). MIC of oxacillin against MRSA was dramatically reduced from 512 to 16 μg ml(-1) in combination with 256 μg ml(-1) of EA08. The fractional inhibitory concentration index of oxacillin was measured at 0.53 in combination with EA08 against MRSA, suggesting that EA08-oxacillin combinations exert synergetic effect against MRSA. The analysis of RT-PCR and Western blotting profiles revealed that EA08 inhibited mRNA expression of mecA gene and production PBP2a, which is a key determinant for β-lactam antibiotic resistance, in a dose-dependent manner. These results indicated that EA08 eventually led to the reduction or inhibition of PBP2a production through translational inhibition in MRSA.
authors.forename: Sung-Hwan
authors.initials: SH
authors.lastname: Eom
authors.forename: Yeoun-Joong
authors.initials: YJ
authors.lastname: Jung
authors.forename: Dae-Sung
authors.initials: DS
authors.lastname: Lee
authors.forename: Mi-Jin
authors.initials: MJ
authors.lastname: Yim
authors.forename: Hye Seon
authors.initials: HS
authors.lastname: Kim
authors.forename: Sang-Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Jeong-In
authors.initials: JI
authors.lastname: Myeong
authors.forename: Jinhwan
authors.initials: J
authors.lastname: Lee
authors.forename: Hyun-Woo
authors.initials: HW
authors.lastname: Kim
authors.forename: Kyoung-Ho
authors.initials: KH
authors.lastname: Kim
authors.forename: Myung-Suk
authors.initials: MS
authors.lastname: Lee
authors.forename: Young-Mog
authors.initials: YM
authors.lastname: Kim
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D010946:Plants, Medicinal; D032104:Poncirus / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D010936:Plant Extracts