Potentiation of antibiotic against Pseudomonas aeruginosa biofilm: a study with plumbagin and gentamicin.

Abstract

Pseudomonas aeruginosa is one of the fatal biofilm-forming pathogens which pose to be a problem in clinical infections, contamination of food and marine ecosystems. In this report, a naphthoquinone-plumbagin has been explored for its antimicrobial (antibacterial and antibiofilm) activity against P. aeruginosa biofilm. The ability of plumbagin to enhance the bioactivity of a known broad-spectrum antibiotic was further assayed by combining the sub-MIC doses of plumbagin with sub-MIC doses of gentamicin against P. aeruginosa biofilm. This combinatorial approach was used for a series of experiments for understanding the mechanism of action for antibiofilm activity against P. aeruginosa (MTCC 424, MTCC 2488). Antibiofilm activity was studied by safranin staining, estimating total protein, visualization of biofilms and extra polymeric substances quantification. Antivirulent activity of these doses was studied by azocasein degradation, expression of virulent factors and molecular docking. Expression of quorum sensing (QS) phenotypes was studied by motility assessment and mRNA expression pattern of virulence genes. It was observed that plumbagin alone and the combinatorial doses of plumbagin and gentamicin exhibit significant antibiofilm and antivirulent activity coupled with the reduction in the expression of QS phenotypes and virulence genes. Molecular docking study revealed that plumbagin had variable affinity for different QS proteins. Low doses of plumbagin and gentamicin exhibit synergistic activity against P. aeruginosa biofilm while maintaining their effectiveness. As the P. aeruginosa biofilms are reservoir of persister bacteria, thus, the increasing concern of antibiotic tolerance has to be dealt with combinatorial approaches. In this report, plumbagin has been explored in potentiating the antibiofilm effect of a broad-spectrum antibiotic gentamicin for better therapeutic efficacy.