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Antibacterial, antibiofilm and antiquorum sensing effects of Thymus daenensis and Satureja hortensis essential oils against Staphylococcus aureus isolates
Author(s) -
Sharifi A.,
Mohammadzadeh A.,
Zahraei Salehi T.,
Mahmoodi P.
Publication year - 2018
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/jam.13639
Subject(s) - satureja , biofilm , carvacrol , thymol , microbiology and biotechnology , minimum inhibitory concentration , quorum sensing , staphylococcus aureus , biology , chemistry , antibacterial activity , food science , minimum bactericidal concentration , essential oil , bacteria , antimicrobial , genetics
Abstract Aims The present study was conducted to investigate the effects of Thymus daenensis and Satureja hortensis essential oils ( EO s) on the planktonic growth, biofilm formation and quorum sensing ( QS ) of some Staphylococcus aureus isolates (strong biofilm producers). Methods and Results Minimum inhibitory concentration ( MIC ) of the EO s, inhibition of biofilm formation as well as disruption of preformed Staph. aureus biofilms were assessed. The antibiofilm activity of the EO s was determined using microtitre plate test (MtP) and scanning electron microscope ( SEM ). The QS inhibitory activity was also examined on the pregrown biofilms by gene expression analysis using quantitative real‐time RT ‐polymerase chain reaction ( PCR ) of hld gene ( RNAIII transcript). Moreover, tetrazolium‐based colorimetric assay ( MTT ) was performed to detect cytotoxic effects of these EO s on the Vero cell line. Finally, the major components of the tested EO s were determined using Gas Chromatography‐Mass Spectrometry ( GC ‐ MS ). The MIC s of T. daenensis and S. hortensis EOs against planktonic cells of the isolates were 0·0625 and 0·125 μ l ml −1 respectively. The minimum bactericidal concentrations for both of the EO s was 0·125 μ l ml −1 . The MtP test showed a significant inhibitory effect of the EO s on the biofilm formation and disruption at sub‐ MIC concentrations. These results were confirmed by SEM . Real‐time PCR revealed a significant down‐regulation of hld gene following treatment with MIC /2 concentration of S. hortensis EO . GC ‐ MS analysis showed that carvacrol, terpinene and thymol were the major components of the applied EO s. Conclusions As selected EO s did not show significant cytotoxic effects even up to tenfold of MIC concentration, the applied EO s seem to be good candidates for preventing of biofilm formation of Staph. aureus cells. Significance and Impact of the Study The present study introduced T. daenensis and S. hortensis EO s as new antibiofilm, and S. hortensis EO as anti‐QS herbal agents with natural origin against Staph. aureus .