Effects of Thymus vulgaris and Cinnamomum verum Essential Oils on bap and ica Gene Expression in Staphylococcus aureus

Staphylococcus aureus can cause a variety of infectious diseases, mainly due to its ability to shift between the planktonic and the biofilm lifestyle. Biofilm infections present a serious problem in human medicine. Biofilm-associated protein (bap) and intercellular adhesin (ica) genes are involved in biofilm formation.

This study evaluated the effect of Thymus vulgaris and Cinnamomum verum essential oils on biofilm formation and expression of icaA, icaD, and bap genes in S. aureus strains.

A total of 20 strains of S. aureus were isolated from the urine of patients. The susceptibility test was performed to determine the effect of minimum inhibitory concentration (MIC) of thyme and cinnamon essential oils on strains by broth dilution method. The expression of icaA and icaD genes was determined by measuring the cognate messenger ribonucleic acid level using real-time polymerase chain reaction (PCR).

The biofilm formation of strains after treatment with the MIC of thyme essential oil was observed as 40% weak and 60% negative biofilms, and with the MIC of cinnamon essential oil as 25% strong and 75% moderate biofilms. Real-time PCR demonstrated that 60% of S. aureus strains treated with thyme and cinnamon essential oils showed a decrease in icaA gene expression. Moreover, 55% and 70% of the strains treated with thyme and cinnamon essential oils had reduced icaD gene expression, respectively. None of the strains of S. aureus had a bap gene.

The present study showed that thyme and cinnamon essential oils reduce the expression of icaA and icaD genes, and cinnamon essential oil is more effective than thyme essential oil.