Epigallocatechin Gallate Induces Upregulation of the Two-Component VraSR System by Evoking a Cell Wall Stress Response in Staphylococcus aureus

Abstract

We previously found that a short exposure of Staphylococcus aureus to subinhibitory (SI) doses of epigallocatechin gallate (EGCG) results in increased cell wall thickness, adaptation, and enhanced tolerance to cell-wall-targeted antibiotics. In this study, the response to EGCG of sigB and vraSR transcription factor mutants was characterized. We show that in contrast to the results observed for wild-type (WT) strains, an S. aureus 315 vraSR null mutant exposed to SI doses of EGCG did not exhibit increased tolerance to EGCG and oxacillin. A diminished increase in tolerance to ampicillin (from 16-fold to 4-fold) and no change in the magnitude of resistance to vancomycin were observed. Preexposure to EGCG enhanced the tolerance of wild-type and sigB null mutant cells to lysostaphin, but this enhancement was much weaker in the vraSR null mutant. Marked upregulation (about 60-fold) of vraR and upregulation of the peptidoglycan biosynthesis-associated genes murA, murF, and pbp2 (2-, 5-, and 6-fold, respectively) in response to SI doses of EGCG were determined by quantitative reverse transcription-PCR (qRT-PCR). EGCG also induced the promoter of sas016 (encoding a cell wall stress protein of unknown function which is not induced in vraSR null mutants) in a concentration-dependent manner, showing kinetics comparable to those of cell-wall-targeting antibiotics. Taken together, our results suggest that the two-component VraSR system is involved in modulating the cell response to SI doses of EGCG.

Epigallocatechin Gallate-Mediated Cell Death Is Triggered by Accumulation of Reactive Oxygen Species Induced via the Cpx Two-Component System in Escherichia coli

“…For example, antibiotics at sub-lethal levels stimulate bacterial resistance ( Harms et al, 2016 ). Indeed, in our work, we found that 400 μg/ml EGCG elevated the resistance of E. coli to β-lactam, but not to spetinomycin or norfloxacin (data not shown), similar to a study demonstrating that EGCG at a sub-inhibitory dose enhances resistance to β-lactam by activating the VasRA system in Staphylococcus aureus ( Levinger et al, 2012 ). Moreover, we observed that ycbB was upregulated.…”

Impact of Nigella sativa and Clove Oils on Cell Wall Genes Expression in Multidrug Resistant Staphylococcus aureus

“…The present results indicated that murF and pbp2 transcriptions were strongly suppressed with a down regulation when S. aureus exposed to 0.5x MICs of both N. sativa and clove oils. The results presented here verified other observations indicating that other plant extracts at sub-inhibitory concentrations induced a cell wall stress response in S. aureus that is modulated by the two-component VraSR system, which in turn enhances the transcription of genes encoding cell wall repair enzymes [19]. Nevertheless, the mechanisms by which S. aureus regulates virulence gene expression are extremely complicated and need further molecular investigations.…”

“…Quantitative RT-PCR (real time polymerase chain reaction) was performed in triplicates using one-step RT-PCR kit with SYBR green (Qiagen, Germany, GmbH) in the Stratagene MX3005P real time PCR machine. The expression patterns of murF and pbp2 genes were measured by qRT-PCR using primers and cycling conditions detailed previously [19]. The relative quantitation of mRNA expression in each sample was normalized to the constitutive expression of the 16S rDNA housekeeping gene.…”

Antimicrobial activity of the chloroform fraction of <i>Drynaria <i>fortunei</i></i> against oral pathogens

“…Some of the polyphenols isolated from plants exhibit anti-carious effects such as growth inhibition and inhibition of glucosyltransferases against mutans streptococci (44)(45)(46). Flavonoid complexes attach with extracellular soluble proteins and the bacterial cell wall, and exhibit antibacterial activity (47,48). As DFCF is composed of many flavonoids, it may exhibit strong antibacterial activity against oral bacteria.…”