Methanolic Extract of Plectranthus tenuiflorus Attenuates Quorum Sensing Mediated Virulence and Biofilm Formation in Pseudomonas aeruginosa PAO1

Abstract

Pseudomonas aeruginosa is an important opportunistic pathogen which causes bacterial keratitis, cyctic fibrosis and other hospital acquired infections. Its ability to form biofilm provides resistance to conventional antibiotics and further corroborates the global health concerns. The antibiotic resistance by P. aeruginosa is due to highly complex cellular signaling system called quorum sensing (QS). As QS controls bacterial pathogenicity and plays a crucial role in biofilm formation, it is a promising alternative target to combat the bacterial virulence. The present study aims to determine the inhibitory activity of Plectranthus tenuiflorus extract on QS and biofilm development in P. aeruginosa PAO1. The crude plant extract inhibited the production of pyocyanin, elastase, protease and chitinase by 71.96 ± 1.82, 38.74 ± 1.29, 30.84 ± 1.20 and 44.75 ± 1.40 % respectively at sub-MIC concentration of 500 µg/ml. The production of biofilm aggravating phenotypes such as exopolysaccharides, alginate and rhamnolipid were also significantly reduced. The biofilm inhibition capability of P. tenuiflorus was further supported by light microscopic and confocal laser scanning microscopic analysis. The phytochemicals such as phytol and mosloflavone were identified from the crude extract using gas chromatography-mass spectrometry (GC-MS). The role of these phytochemicals in down regulation of QS in P. aeruginosa was further confirmed by in silico studies targeting transcriptional receptors, LasR and RhlR of the QS regulatory network. The in vitro and docking studies suggest the anti QS potential of P. tenuiflorus in combating the bacterial pathogenesis.

Analysis of Antiquorum-Sensing and Antibiofilm Activity by Pomelo Peel Extract (Citrus maxima) on Multidrug-Resistance Pseudomonas aeruginosa

“…Similar results were also obtained in a study conducted by Hnamte et al (2018) in which there was a significant reduction in biofilm formation in the group given the extract Plectranthus tenuiflorus , which contains flavonoids, compared with a thick biofilm and solid-generated in the group controls, who were not given the extract. Biofilm formation in P. aeruginosa PAO1 was found to be reduced by 44% on treatment with P. tenuiflorus extract at a sub-MIC dose (500 μg/mL) [ 36 ]. In another study, the effect of antibiofilm was also evaluated with the addition of leaf extract from Juglans regia containing active compounds of phenolic acids and flavonoids on P. aeruginosa .…”

Plant Derived Natural Products against Pseudomonas aeruginosa and Staphylococcus aureus: Antibiofilm Activity and Molecular Mechanisms

“…In addition to pure flavonoids, crude extracts containing flavonoid derivatives as principal constituents also attenuated QS-mediated virulence and biofilm formation. In particular, the binding affinity of mosloflavone for RhlR, detected in the methanolic extract of Plectranthus tenuiflorus [60], was observed to be comparatively higher than its natural ligand, while kaempferol constituted the major constituent of Centella asiatica, a herb with proven anti-QS properties [61].…”