Leaf Extracts of Mangifera indica L. Inhibit Quorum Sensing - Regulated Production of Virulence Factors and Biofilm in Test Bacteria.

Ibrahim M Alhazza,Abdullah S Al-Thubiani,Iqbal Ahmad,Farrukh Aqil,Hussein H Abulreesh,Fohad M Husain

doi:10.3389/fmicb.2017.00727

Abstract

Quorum sensing (QS) is a global gene regulatory mechanism in bacteria for various traits including virulence factors. Disabling QS system with anti-infective agent is considered as a potential strategy to prevent bacterial infection. Mangifera indica L. (mango) has been shown to possess various biological activities including anti-QS. This study investigates the efficacy of leaf extracts on QS-regulated virulence factors and biofilm formation in Gram negative pathogens. Mango leaf (ML) extract was tested for QS inhibition and QS-regulated virulence factors using various indicator strains. It was further correlated with the biofilm inhibition and confirmed by electron microscopy. Phytochemical analysis was carried out using ultra performance liquid chromatography (UPLC) and gas chromatography–mass spectrometry (GC-MS) analysis. In vitro evaluation of anti-QS activity of ML extracts against Chromobacterium violaceum revealed promising dose-dependent interference in violacein production, by methanol extract. QS inhibitory activity is also demonstrated by reduction in elastase (76%), total protease (56%), pyocyanin (89%), chitinase (55%), exopolysaccharide production (58%) and swarming motility (74%) in Pseudomonas aeruginosa PAO1 at 800 μg/ml concentration. Biofilm formation by P. aeruginosa PAO1 and Aeromonas hydrophila WAF38 was reduced considerably (36–82%) over control. The inhibition of biofilm was also observed by scanning electron microscopy. Moreover, ML extracts significantly reduced mortality of Caenorhabditis elegans pre-infected with PAO1 at the tested concentration. Phytochemical analysis of active extracts revealed very high content of phenolics in methanol extract and a total of 14 compounds were detected by GC-MS and UPLC. These findings suggest that phytochemicals from the ML could provide bioactive anti-infective and needs further investigation to isolate and uncover their therapeutic efficacy.

Highlights

Development of multidrug resistance in bacterial pathogens has created special problem for antibiotic therapy (MacPherson et al, 2009)
Different extracts of Mango leaf (ML) were obtained in petroleum ether, benzene, ethyl acetate, acetone and methanol and tested for Quorum sensing (QS) modulatory activity against C. violaceum (CV12472)
In many bacteria virulence factors are regulated through QS, a cell density-dependent global gene regulatory mechanism

Summary

Introduction

Development of multidrug resistance in bacterial pathogens has created special problem for antibiotic therapy (MacPherson et al, 2009). New drug target identification and development of new therapeutics to combat bacterial infection is currently needed. Many researchers have indicated that QS which regulates the expression of many virulence traits in pathogenic bacteria as an attractive anti-infective drug target (Smith and Iglewski, 2003; Rasmussen and Givskov, 2006). P. aeruginosa, opportunistic pathogens, preferably infects the individuals with defective immune systems (Van Delden and Iglewski, 1998). The production of the majority of the virulence factors has been demonstrated to be regulated by one of the three QS systems, LasIR, RhlIR and PQS (McKnight et al, 2000; Smith and Iglewski, 2003; Jimenez et al, 2012)

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Results

Conclusion