Potentiation of Antibiotic against Psedomonas aeruginosa biofilm: A study with Plumbagin and Gentamicin.

AIM: 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 napthoquinone - 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.

METHODS AND RESULTS: This combinatorial approach was used for a series of experiments for understanding the mechanism of action for antibiofilm activity against P. aeruginosa (MTCC424, MTCC2488). Antibiofilm activity was studied by safranin staining, estimating total protein, visualisation of biofilms and EPS 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 expression of QS phenotypes and virulence genes. Molecular docking study revealed that Plumbagin had variable affinity for different QS proteins.

CONCLUSION: Low doses of Plumbagin and Gentamicin exhibit synergistic activity against P. aeruginosa biofilm whilst maintaining their effectiveness This article is protected by copyright. All rights reserved.