Effect of Satureja montana L. essential oil on quorum sensing-controlled virulence factors and biofilm production of Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the most common causes of nosocomial infections worldwide, associated with high morbidity and mortality rates. It is one of the most difficult bacteria to treat because of its innate, acquired, and adaptive antibiotic resistance, which is controlled by a complex interplay of mechanisms. Adjuvant strategies targeting P. aeruginosa resistance mechanisms could rejuvenate conventional antibiotic therapy by increasing drug efficacy and slowing antibiotic resistance. Therefore, the aim of this study was to investigate, for the first time, the effect of Satureja montana L. essential oil and its major constituent thymol (56.5%) on quorum sensing controlled virulence factors and biofilm production of P. aeruginosa individually and in combination with tobramycin. Both essential oil and thymol at a concentration of 0.5 mg/mL inhibited the growth of planktonic P. aeruginosa PAO1 and acted synergistically with the reference antibiotic at subinhibitory concentrations. Furthermore, S. montana essential oil and thymol synergistically with tobramycin decreased the swarming and proteolytic activity of P. aeruginosa strains PAO1, PA14, and ATCC 27853. In contrast, they showed antagonistic effects in the same combination, resulting in increased pyocyanin production by P. aeruginosa PAO1. Despite the demonstrated inhibitory effect against planktonic P. aeruginosa ATCC 27853, their synergistic-antagonistic activity on biofilm production was highly variable and strongly dependent on a narrow concentration range. Our study contributed to a better understanding of the influence of essential oils on quorum sensing-controlled virulence and biofilm formation.

 

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Artikel online veröffentlicht:
16. November 2023