Effects of cholesterol on Helicobacter pylori growth and virulence properties in vitro

Background: Colonization of the gastric mucosa by Helicobacter pylori is often associated with chronic gastric pathologies in humans. Development of disease correlates with the presence of distinct bacterial pathogenicity factors, such as the cag type IV secretion system (cag‐T4SS), the vacuolating cytotoxin (VacA), or the ability of the bacteria to acquire and incorporate cholesterol from human tissue. Materials and Methods: The in vitro growth of H. pylori requires media (Brucella broth) complemented with vitamins and horse serum or cyclodextrins, prepared as blood agar plates or liquid cultures. Liquid cultures usually show a slow growth. Here, we describe the successful growth of H. pylori strains 26695, P217, P12, and 60190 on serum‐free media replacing serum components or cyclodextrins with a commercially available cholesterol solution. Results: The effects of cholesterol as a substitute for serum or cyclodextrin were rigorously tested for growth of H. pylori on agar plates in vitro, for its general effects on bacterial protein synthesis (the proteome level), for H. pylori’s natural competence and plasmid DNA transfer, for the production of VacA, and the general function of the cag‐pathogenicity island and its encoded cag‐T4SS. Generally, growth of H. pylori with cholesterol instead of serum supplementation did not reveal any restrictions in the physiology and functionality of the bacteria except for strain 26695 showing a reduced growth on cholesterol media, whereas strain 60190 grew more efficient in cholesterol‐ versus serum‐supplemented liquid medium. Conclusions: The use of cholesterol represents a considerable option to serum complementation of growth media for in vitro growth of H. pylori.