Myricetin as an Antivirulence Compound Interfering with a Morphological Transformation into Coccoid Forms and Potentiating Activity of Antibiotics against <i>Helicobacter pylori</i>

• Main Authors: Paweł Krzyżek, Paweł Migdał, Emil Paluch, Magdalena Karwańska, Alina Wieliczko, Grażyna Gościniak
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: International Journal of Molecular Sciences
• Subjects: <i>Helicobacter pylori</i>; coccoid forms; morphological transformation; myricetin; checkerboard assay; synergism
• Online Access: https://www.mdpi.com/1422-0067/22/5/2695

<i>Helicobacter pylori</i>, a gastric pathogen associated with a broad range of stomach diseases, has a high tendency to become resistant to antibiotics. One of the most important factors related to therapeutic failures is its ability to change from a spiral to a coccoid form. Therefore, the main aim of our original article was to determine the influence of myricetin, a natural compound with an antivirulence action, on the morphological transformation of <i>H. pylori</i> and check the potential of myricetin to increase the activity of antibiotics against this pathogen. We observed that sub-minimal inhibitory concentrations (sub-MICs) of this compound have the ability to slow down the process of transformation into coccoid forms and reduce biofilm formation of this bacterium. Using checkerboard assays, we noticed that the exposure of <i>H. pylori</i> to sub-MICs of myricetin enabled a 4–16-fold reduction in MICs of all classically used antibiotics (amoxicillin, clarithromycin, tetracycline, metronidazole, and levofloxacin). Additionally, RT-qPCR studies of genes related to the <i>H. pylori</i> morphogenesis showed a decrease in their expression during exposure to myricetin. This inhibitory effect was more strongly seen for genes involved in the muropeptide monomers shortening (<i>csd3</i>, <i>csd6</i>, <i>csd4</i>, and <i>amiA</i>), suggesting their significant participation in the spiral-to-coccoid transition. To our knowledge, this is the first research showing the ability of any compound to synergistically interact with all five antibiotics against <i>H. pylori</i> and the first one showing the capacity of a natural substance to interfere with the morphological transition of <i>H. pylori</i> from spiral to coccoid forms.