Abstract:
Pseudomonas aeruginosa is the causative agent of several life-threatening human infections.
Like many other pathogens, P. aeruginosa exhibits quorum sensing (QS) controlled virulence factors
such as biofilm during disease progression, complicating treatment with conventional antibiotics.
Thus, impeding the pathogen’s QS circuit appears as a promising alternative strategy to overcome
pseudomonas infections. In the present study, Calpurnia aurea were evaluated for their antibacterial
(minimum inhibitory concentrations (MIC)), anti-quorumsensing/antivirulence (AQS), and antibiofilm
potential against P. aeruginosa. AQS and antivirulence (biofilm formation, swimming, and swarming
motility) activities of plant extracts were evaluated against Chromobacterium violaceum and P. aeruginosa,
respectively. The in vitro AQS potential of the individual compounds were validated using in
silico molecular docking. Acetone and ethanolic extracts of C. aurea showed MIC at 1.56 mg/mL.
The quantitative violacein inhibition (AQS) assay showed ethyl acetate extracts as the most potent at
a concentration of 1 mg/mL. GCMS analysis of C. aurea revealed 17 compounds; four (pentadecanol,
dimethyl terephthalate, terephthalic acid, and methyl mannose) showed potential AQS through
molecular docking against the CviR protein of C. violaceum. Biofilm of P. aeruginosa was significantly
inhibited by 60% using 1-mg/mL extract of C. aurea. Confocal laser scanning microscopy correlated
the findings of crystal violet assay with the extracts significantly altering the swimming motility.
C. aurea extracts reduced the virulence of pseudomonas, albeit in a strain- and extract-specific manner,
showing their suitability for the identification of lead compounds with QS inhibitory potential for the
control of P. aeruginosa infections.
