Serratia marcescens is one of the important nosocomial pathogens which rely on quorum sensing (QS) to regulate the production of biofilm and several virulence factors. Hence, blocking of QS has become a promising approach to quench the virulence of S. marcescens. For the first time, QS inhibitory (QSI) and antibiofilm potential of Actinidia deliciosa have been explored against S. marcescens clinical isolate (CI). A. deliciosa pulp extract significantly inhibited the virulence and biofilm production without any deleterious effect on the growth. Vanillic acid was identified as an active lead responsible for the QSI activity. Addition of vanillic acid to the growth medium significantly affected the QS regulated production of biofilm and virulence factors in a concentration dependent mode in S. marcescens CI, ATCC 14756 and MG1. Furthermore vanillic acid increased the survival of Caenorhabditis elegans upon S. marcescens infection. Proteomic analysis and mass spectrometric identification of differentially expressed proteins revealed the ability of vanillic acid to modulate the expression of proteins involved in S-layers, histidine, flagellin and fatty acid production. QSI potential of the vanillic acid observed in the current study paves the way for exploring it as a potential therapeutic candidate to treat S. marcescens infections.
Urinary tract infections are the utmost common bacterial infections caused by Proteus mirabilis, Pseudomonas aeruginosa, Escherichia coli, and Serratia marcescens. These uropathogens resist the action of several antibiotics due to their ability to form biofilms. Most of these bacterial pathogens use the quorum sensing (QS) machinery to co-ordinate their cells and regulate several virulence factors and biofilm formation. On the other hand, the anti-quorum sensing (anti-QS) and antibiofilm potential of silver nanoparticles have been well reported against certain bacterial pathogens, but to the best of our knowledge, no report is available against the pathogenicity of uropathogens in particular S. marcescens and P. mirabilis. Therefore, the present study is primarily focused on the anti-QS and antibiofilm potential of Piper betle-based synthesized silver nanoparticles (PbAgNPs) against S. marcescens and P. mirabilis. Initially, the silver nanoparticles were synthesized by the aqueous extract of P. betle and characterized by UV-absorbance spectroscopy, XRD, FT-IR, SEM, TEM, and DLS. The synthesized silver nanoparticles were assessed for their anti-QS activity and the obtained results revealed that the PbAgNPs inhibited the QS-mediated virulence factors such as prodigiosin, protease, biofilm formation, exopolysaccharides and hydrophobicity productions in uropathogens. The gene expression analysis divulged the downregulation of fimA, fimC, flhD, and bsmB genes in S. marcescens and flhB, flhD, and rsbA genes in P. mirabilis, respectively. The in vivo Caenorhabditis elegans assays revealed the non-toxic and anti-adherence efficiency of PbAgNPs. Furthermore, the non-toxic effect of PbAgNPs was also confirmed through peripheral blood mononuclear cells and normal lung epithelial cells. Therefore, the contemporary study demonstrates the use of PbAgNPs as a possible alternative toward conventional antibiotics in controlling QS and biofilm-related uropathogen infections.
In the present study, the antibiofilm, antipathogenic and anticarotenogenic potential ofl-ascorbyl 2,6-dipalmitate (ADP) against methicillin-resistantStaphylococcus aureus(MRSA) has been evaluated.
Aim: To establish Caenorhabditis elegans based in vivo method for screening bioactives from marine sponge associated bacteria (SAB) against Vibrio species. Methods and Results: About 256 SAB isolates were screened for their ability to rescue C. elegans infected with Vibrio species. The chloroform extract of the positive isolate was subjected to column fractionation and purity of the active fraction was analysed using HPLC. Further, the components were elucidated using GC/MS. The active fraction was tested for its in vivo rescue activity, antibacterial and anti-QS activity. In vivo colonization reduction and biofilm inhibition efficiency were assessed using GFP-tagged V. alginolyticus using confocal laser scanning microscopy (CLSM). The ability of the active fraction in modulating expression of V. alginolyticus quorum sensing (QS) regulators luxT and lafK was measured using real-time PCR. The results indicated that the chloroform extract of SAB4.2 displayed significant rescue activity against V. alginolyticus by inhibiting the QS pathway. HPLC analysis of the active fraction revealed a single major peak and GC/MS analysis suggested Pyrrolo [1,2-a]pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl) as the major constituent. The potent bacterial isolate was identified as Alcaligenes faecalis. Conclusions: In vivo screening using C. elegans identified a marine isolate that inhibits the virulence of V. alginolyticus by interrupting the QS pathway. Significance and Impact of the Study: The study provides a C. elegans based in vivo screening method for identifying bioactives from natural resources by overcoming the disadvantages of traditional in vitro plate assays.
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