Clove oil down regulates the expression of genes encoding the efflux pump, virulence factors and quorum sensing in MDR Pseudomonas aeruginosa

Abstract

Abstract Background The emergence of multi-drug resistant Pseudomonas aeruginosa and development of new resistant phenotypes are considered major public health issues. The present work aims to evaluate clove oil effect as anti-bacterial, anti-virulence, efflux pump and quorum sensing inhibitor. Results Susceptibility of P. aeruginosa to antimicrobials and clove oil either alone or combined with fluoroquinolones was tested using agar dilution method. Results revealed that 1/2 MIC of clove oil combined with fluoroquinolones showed synergism in 90% isolates. Effect of sub-MICs of clove oil on biofilm formation and some virulence factors was investigated. A significant reduction in virulence attributes as well as in the expression of efflux pump encoding genes (mexA and mexB) and quorum sensing regulatory genes (lasI, lasR, pqsA, pqsR) was recorded with 1/2 MIC of clove oil. An animal model for wound infection was used to assess the therapeutic effect of clove oil, in vivo. Clove oil reduced the bacterial burden in infected wounds by 92% and caused a decline in cell infiltration in excisional wound skin tissue. Conclusions Synergistic combinations between fluoroquinolones and sub-MICs of clove oil can be used to modify the antimicrobial resistance level. Clove oil (1/2 MIC) was reported to significantly decrease the expression of efflux and quorum sensing genes followed by reduction in expression of virulence machinery in P. aeruginosa. Clove oil may be used as an antimicrobial adjuvant in treatment protocols of P. aeruginosa infections by lowering the effective doses of the current antimicrobials.