Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Responses in the Expression of Extracellular Proteins in Methicillin-Resistant Staphylococcus aureus Treated with Rhodomyrtone: Monton Visutthi , Potjanee Srimanote , Supayang Piyawan Voravuthikunchai; J. Microbiol. 2011;49(6):956-964. Published online December 28, 2011; DOI: https://doi.org/10.1007/s12275-011-1115-0

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Abstract: Rhodomyrtone from a medicinal plant species, Rhodomyrtus tomentosa, is a challenged effective agent against Gram-positive bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA). The present study was undertaken to provide insight into MRSA extracellular protein expression following rhodomyrtone treatment. Secreteomic approach was performed on a representative clinical MRSA isolate exposing to subinhibitory concentration rhodomyrtone (0.174 μg/ml). The identified extracellular proteins of a response of MRSA to rhodomyrtone treated condition were both suppressed and overexpressed. Staphylococcal antigenic proteins, immunodominant antigen A (IsaA) and staphylococcal secretory antigen (SsaA) involved in cell wall hydrolysis were downregulated after the treatment. The results suggested that rhodomyrtone may interfere with WalK/WalR (YycG/YycF) system. Other enzymes such as lipase precursor and another lipase, glycerophosphoryl diester phosphodiesterase, were absent. In contrast, cytoplasmic proteins such as SpoVG and glycerol phosphate lipoteichoic acid synthase, and ribosomal proteins were found in the treated sample. Appearance of several cytoplasmic proteins in the treated culture supernatant revealed that the bacterial cell wall biosynthesis was disturbed. This finding provides a proteomic mapping of extracellular proteins after rhodomytone treatment. Extensive investigation is required for this natural compound as it has a great potency as an alternative anti-MRSA drug.

Synergistic Effects of the Combination of Galangin with Gentamicin against Methicillin-Resistant Staphylococcus aureus: Young-Seob Lee , Ok-Hwa Kang , Jang-Gi Choi , You-Chang Oh , Hee-Sung Chae , Jong Hak Kim , Hyun Park , Dong Hwan Sohn , Zheng-Tao Wang , Dong-Yeul Kwon; J. Microbiol. 2008;46(3):283-288. Published online July 5, 2008; DOI: https://doi.org/10.1007/s12275-008-0012-7

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Abstract: The antimicrobial killing activity toward methicillin-resistant Staphylococcus aureus (MRSA) has been a serious emerging global issue. New effective antimicrobials and/or new approaches to settle this issue are urgently needed. The oriental herb, Alpinia officinarum, has been used in Korea for several hundreds of years to treat various infectious diseases. As it is well known, one of the active constituents of Alpinia officinarum is galangin. Against the 17 strains, the minimum inhibitory concentrations (MICs) of galangin (GAL) were in the range of 62.5~125 μg/ml, and the MICs of gentamicin (GEN) ranged from 1.9 μg/ml to 2,000 μg/ml. The fractional inhibitory concentrations (FICs) of GAL, in combination with GEN, against 3 test strains were 0.4, 3.9, and 250 μg/ml, and were all 15.62 μg/ml in GEN. The FIC index showed marked synergism in the value range of 0.19 to 0.25. By determining time-kill curves, also confirmed the low synergism of the GAL and GEN combination against 4 h, 8 h, 12 h, and 24 h cultured MRSA. The time-kill study results indicated a low synergistic effect against 3 test strains. Thus, the mixture of GAL and GEN could lead to the development of new combination antibiotics against MRSA infection.

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