The effect of sub-inhibitory concentration of clove essential oil on the expression of <i>Pseudomonas aeruginosa</i> virulence genes

Abstract

Clove essential oil (CEO) has been reported to be used in the treatment of bacterial, fungal, and yeast infections. It has also been reported to have positive impact on the virulence factors in some pathogenic bacteria. This study aims to investigate the growth inhibitory activity of CEO against Pseudomonas aeruginosa and its effect on the expression of key virulence genes for biofilm formation and protease production. The antibacterial activity in respect to the minimum inhibitory concentration (MIC) of clove oil against six multidrug-resistant Pseudomonas aeruginosa strains was evaluated using the broth dilution method. The cytotoxic, protease production, and biofilm inhibitory effects of CEO were evaluated following standard protocols. The effect of the oil at sub-MIC concentrations on the expression of the virulence genes; aprA and pelF was evaluated by Real-Time Polymerase Chain Reduction (RT-PCR) technique. Treatment with CEO resulted in a significant inhibition of biofilm formation and protease production in Pseudomonas aeruginosa. RT-PCR analysis showed a reduction in the expression of the two virulence genes; pelF and aprA. These findings suggest a potential for the use of CEO as alternative antibacterial agent for the treatment of infections due to multidrug-resistant Pseudomonas aeruginosa.