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- Food-Borne Enterococci and Their Resistance to Oxidative Stress
- Barbora Vlková , Tomá&# , Gabriel Minárik , Lubomíra Tóthová , Hana Drahovská , Ján Tur&# , Peter Celec
- J. Microbiol. 2011;49(4):657-662. Published online September 2, 2011
- DOI: https://doi.org/10.1007/s12275-011-0296-x
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- 4 Scopus
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Abstract
- Enterococci are important food-borne pathogens that cause serious infections. Several virulence factors have been described including aggregation substance, gelatinase, cytolysin, and enterococcal surface protein. The ability to cause infections is mainly dependent on the response to oxidative stress due to the production of reactive oxygen species by immune cells. The aim of our study was to analyze the resistance of enterococcal strains from food to clinically relevant antiseptic agents with regard to the presence of selected virulence factors, and to uncover potential mechanisms of the antioxidative resistance. Eighty-two enterococcal isolates from Bryndza cheese were tested using in vitro growth assays to study the ability of these isolates to survive exposure to antiseptic agents – hydrogen peroxide, hypochlorite, and chlorhexidine. Virulence genotypes of the isolates were determined by PCR, and RT real time PCR was used for gene expression under oxidative stress. Resistance against antiseptic agents depends on the concentration of applied chemicals, on the time of exposure, but also on virulence factors of the enterococcal strains. Oxidative stress induces the expression of antioxidative enzymes and down-regulates the expression of prooxidative enzymes. These effects are dependent on the virulence genotype of the enterococcal strains. These findings are important for future research, especially concerning the role of enterococci in oral diseases.
- Examination of the Antioxidant Potential of Pycnogenol under Conditions of Oxidative Stress in Escherichia coli Mutants Deficient in HP1 and Superoxide Dismutase Activities
- Jeong A Youm , Young Gon Kim
- J. Microbiol. 2003;41(1):28-33.
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Abstract
- Pycnogenol (PYC) is believed to have potential as a therapeutic agent against free radical-mediated oxidative stress. It is important, therefore, to understand the interactions between PYC and cellular defenses against oxidative stress. Toward this end, we analyzed the survival rates on the gene expression responses of E. coli sod katG mutants to PYC after pre-treatment of PQ or H_2O_2-mediated stress under aerobic conditions. We identified SOD induced by PYC, but not HP1 in sod katG mutants. A striking result was the PYC induction of SOD with antioxidant property in single katG mutant cells, particularly MnSOD and CuZnSOD. These inductions were further increased with oxidative stress, while HP1 was not induced in these conditions. The effects of pycnogenol treatment on these cells depend in part on its concentration on the stress response. Protective effects of PYC exposure which affected gene expression in cells were consistent with cell survival rates. Our results demonstrate that pycnogenol may alter the stress response gene expression in a specific manner such as SoxRS because PYC induction of single mutant only worked under increased PQ stress. All together our data indicate that SOD activity is essential for the cellular defense against PQ-mediated oxidative stress, suggesting that PYC may not be effective as an antioxidant in only oxidative stress conditions. On the other hand, it was expected that PYC may play a role as a pro-oxidant and if it is available for use, it should be evaluated carefully.
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