Anti-biofilm activity of Quercus infectoria G. Olivier against methicillin-resistant Staphylococcus aureus
ABSTRACT To establish the effect of Quercus infectoria G. Olivier extract and its main constituent, tannic acid, on staphylococcal biofilm and their anti-biofilm mechanisms.
Anti-biofilm activity of the plant materials on clinical isolated of methicillin-resistant Staphylococcus aureus and methicillin-susceptible Staph. aureus was employed using a crystal violet-stained microtiter plate method. The extract at minimum inhibitory concentration (MIC; 0.25 mg ml(-1)) was significantly reduced the biofilm formation of the isolates (P < 0.05). The effect on staphylococcal cell surface hydrophobicity (CSH) of the test compounds was investigated as a possible mode of action of the anti-biofilm activity. The hydrophobicity index of all the bacterial isolates increased following treatment with supra-MIC, MIC and sub-MIC of the extract and tannic acid. Observation of the treated bacterial cells by electron microscopy revealed that the test compounds caused clumps of partly divided cocci with thickened and slightly rough cell wall.
The results indicated that Q. infectoria extract and tannic acid affected staphylococcal biofilm formation and their effect on bacterial CSH and cell wall may involve in the anti-biofilm activity.
This evidence highlighted the anti-biofilm potency of the natural products and clarified their anti-biofilm mechanisms.
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ABSTRACT: Staphylococcus aureus is a human commensal and pathogen that is capable of forming biofilms on a variety of host tissues and implanted medical devices. Biofilm-associated infections resist antimicrobial chemotherapy and attack from the host immune system, making these infections particularly difficult to treat. In order to gain insight into environmental conditions that influence S. aureus biofilm development, we screened a library of small molecules for the ability to inhibit S. aureus biofilm formation. This led to the finding that the polyphenolic compound tannic acid inhibits S. aureus biofilm formation in multiple biofilm models without inhibiting bacterial growth. We present evidence that tannic acid inhibits S. aureus biofilm formation via a mechanism dependent upon the putative transglycosylase IsaA. Tannic acid did not inhibit biofilm formation of an isaA mutant. Overexpression of wildtype IsaA inhibited biofilm formation whereas overexpression of a catalytically dead IsaA had no effect. Tannin-containing drinks like tea have been found to reduce methicillin resistant S. aureus nasal colonization. We found that black tea inhibited S. aureus biofilm development and that an isaA mutant resisted this inhibition. Antibiofilm activity was eliminated from tea when milk was added to precipitate the tannic acid. Finally, we developed a rodent model for S. aureus throat colonization and found that tea consumption reduced S. aureus throat colonization via an isaA-dependent mechanism. These findings provide insight into a molecular mechanism by which commonly consumed polyphenolic compounds, such as tannins, influence S. aureus surface colonization.Infection and immunity 12/2012; 81:(2). DOI:10.1128/IAI.00877-12 · 3.73 Impact Factor
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