SKIN CARE
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Quorum sensing inhibition to restrain bacteria
Sabrina Leoty-Okombi, Manon Gault, Valérie Andre-Frei, Philip Ludwig - BASF
Bacteria use a cell-to-cell communication system called quorum sensing (QS) to share information about cell density and adjust gene expression accordingly.1
QS controls genes
that direct activities that are beneficial when performed by groups of bacteria acting in synchrony.2 Processes controlled by QS include
antibiotic production, biofilm formation, and virulence factor secretion are responsible for harmful bacterial expression in body and on human skin. QS systems rely on the production and sensing of extracellular signals.1 In our investigations, we focused on
two bacteria. The first one is Pseudomonas aeruginosa, a gram-negative-bacteria, known to be involved in skin infection, in green nail syndrome and less severe conditions like folliculitis, and skin rashes. P. aeruginosa uses QS molecules belonging
to Acyl Homoserine Lactone (AHL) family of Pseudomonas Quinolone Signal (PQS) to express an arsenal of virulent traits that damage host cells. The virulence factors can be classified in two categories.3 ■ Surface-bound virulence factors: flagella and pili are needed for the bacteria’s motility, and to bind to host cells. Moreover, the binding of these appendages to Toll-like receptor 5 (TLR5) can trigger inflammation. ■ Secreted virulence factors comprise toxins, proteases which can damage the skin barrier and pigmented metabolites like phenazines inducing cell damage mainly triggered through formation of reactive oxygen species and alteration of cytokines production. In a second case study, we used gram-
positive Staphylococcus aureus. S. aureus is an opportunistic bacterium involved in inflammatory skin conditions.4
Its colonization
is promoted by skin dryness and skin barrier disruption. S. aureus uses thiopeptides called autoinducing peptide (AIP) to coordinate biofilm synthesis and secretion of virulence factors. These virulence factors are toxins, proteases and lipases that induce skin barrier disruption.5 Since harmful bacteria expression on the skin is controlled by QS, decreasing this communication through a quorum quenching mechanism represents an attractive means to develop novel cosmetics to fight skin microbiota’s harmful effects on skin, to protect skin health and wellbeing while preserving the skin’s microbiota balance and preventing appearance of resistance from bacteria.
www.personalcaremagazine.com Our aim was to seek natural plant extracts
able to quench Quorum Sensing signals from P. aeruginosa and S. aureus. Then, we checked if their effect on QS was followed by a decrease in virulence, determined by both bacteria motility and lipase secretion.
Materials Molecules Pseudomonas aeruginosa ATCC15692 was purchased from Pasteur Institute as well as Staphylococcus aureus ATCC35556. Lysogeny Broth (LB) and Tryptic Soy Broth (TSB) media were obtained from Sigma. Film tracer kit used was from Invitrogen. Quorum Sensing standard molecules C4-
HSL, 3-oxo-C12-HSL and PQS were supplied by Sigma Aldrich (France) and AIP I was provided by Eugentec Anaspec (France). Quorum sensing inhibitor molecule furanone was obtained from Sigma Aldrich (France).
Equipment Standard laboratory equipment was used in this work, namely microplates, petri dishes (motility), Erlenmeyer flasks, magnetic stirrers, Micropipette, mixer, analytical balance, incubator. Furanone and lipase substrate were provided by Sigma (France). Equipment to measure the optical density
of bacteria: nano liquid chromatography (LC) coupled to high resolution mass spectrometry (HRMS) from SHIMADZU or Fisher
Thermoscientific was used for QS molecule quantification. Chromatography column C-18 was provided by Dionex.
Methods Botanical extraction and plant material Litchi chinensis extract used in this study is obtained after glycolic extraction and filtration. This extract contains some flavonoids (tannins or flavanol and flavonols). Pueraria lobata extract used in the
following experiment is a hydroalcoholic extract containing some flavonoids namely isoflavones.
Inhibition of secretion of P. aeruginosa and S. aureus quorum sensing molecule Bacterial culture We developed culture conditions to obtain a bacterial density enabling bacteria to secrete AHL, PQS and AIP in enough quantity to be detected by LC/MS-MS.6,7 P. aeruginosa ATCC15692 was grown in LB medium at 37°C in aerobiosis, in absence (untreated control) or presence of reference inhibitor furanone at 0.2% or Litchi extract at 0.2 and 0.4%. Staphylococcus aureus: ATCC35556, was
grown in TSB, at 37°C in aerobiosis in absence (untreated control) or presence of Pueraria lobata extract. After 24 hours, culture media were then
centrifuged, and supernatants were collected for QS molecule quantification.
February 2024 PERSONAL CARE
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