Bacteria within a biofilm have a distinct phenotype from planktonic cells and generally show higher tolerance to antimicrobial agents, such as disinfectant treatments and antibiotics. Due to the increased tolerance against antimicrobial treatments, biofilms are hard to eradicate and they cause all kinds of problems in medical and industrial settings. Therefore, the purpose of this study was to examine the influence of Thymus vulgaris essential oil on the initial adhesion and preformed biofilm of Salmonella Enteritidis. Results for antimicrobial activity of Th. vulgaris essential oil obtained using broth microdilution method against S. Enteritidis were identical for all tested isolates (MIC/MFC=0.156/0.3125 µL/mL). In order to understand the anti-biofilm action of essential oil (EO), its effect was tested on both the initial cell attachment by planktonic cells as well as on preformed biofilms. Obtained results indicated that the effect of Th. vulgaris essential oil on initial cell attachment of tested isolates SE4, SE5, SE7 and SE9 was dosage dependent manner, although even at 0.5×MIC biomass attachment was reduced by 74.2%, 77.7%, 73.6% and 70.1%, respectively. Fairly high, but not complete, inhibition of cell attachment was achieved using 1×MIC of this EO. Using 1×MIC, biomass attachment of tested isolates SE4, SE5, SE7 and SE9 was reduced for 91.4%, 90.2%, 90.6% and 88.4%, respectively. When the same EO was tested against a preformed biofilm, its inhibitory effect was reduced greatly.
Salmonella Enteritidis, biofilm, Thymus
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