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The antibacterial effects of tea polyphenols (TPP) extracted from Korean green tea (Camellia sinensis) against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) were evaluated. Characterization of the minimal inhibitory concentration (MIC) of oxacillin for 30 S. aureus strains isolated from patients treated with oxacillin identified 13 strains with an oxacillin MIC C 4 lg/mL as methicillinresistant Staphylococcus aureus (MRSA) (range: 8 to 512 lg/ mL), while 17 strains were methicillin-susceptible Staphylococcus aureus (MSSA) (range: 0.25-0.5 lg/mL). The MICs of TPP ranged from 50 to 180 lg/mL for both the MSSA and the MRSA strains. The MICs of oxacillin for each of the 13 MRSA strains were reduced between 8-and 128-fold when these strains were coincubated with sub-MIC (B0.59 MIC) levels of TPP, demonstrating that the combination of TPP plus oxacillin was synergistic for all of the clinical MRSA isolates. Two-dimensional polyacrylamide gel electrophoresis identified 14 extracellular proteins of MRSA-13 down-regulated and 3 proteins up-regulated by exposure to TPP. These studies demonstrate that TPP can differentially stimulate the expression of various proteins in these bacteria and synergize the bactericidal activity of oxacillin for MRSA.

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The purpose of this work was to investigate the induction of stress shock proteins in Burkholderia sp. YK-2 in response to the phenoxyherbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The stress shock proteins, which contribute to the resistance of the cytotoxic effect of 2,4-D, were induced at different 2,4-D concentrations in exponentially growing cultures of Burkholderia sp. YK-2. This response involved the induction of a 43-kDa DnaK and 41-kDa GroEL proteins, characterized by SDS-PAGE and Western blot by use of the anti-DnaK and anti-GroEL monoclonal antibodies. The total stress shock proteins were analyzed by 2-D PAGE. Survival of Burkholderia sp. YK-2 with time in the presence of different concentrations of 2,4-D was monitored, and viable counts paralleled the induction of the stress shock proteins in this strain.