The role of mucus in adhesion and invasion of foodborne pathogens: challenges in current human intestinal model

Cell adhesion and invasion are the fundamental processes of bacterial pathogenicity that govern their probable transmission pathways. The gastrointestinal mucosa, which is lined with epithelial cells, is the primary route used by the foodborne pathogen to reach systemic organs and tissues. This mucosa is protected by a layer of continually secreted mucus, which is thought to be the initial line of defence against pathogen invasion. Studies on the adhesion and invasion ability of foodborne pathogens using Caco-2 monoculture have been comprehensively reported. This cell line, however, is classified as non-mucusproducing cells. Since the mechanism of adhesion and invasion is largely depending on the presence of mucus, the use of this cell line to study how foodborne pathogens cross the intestinal barrier has raised concerns as the establishment of the typical components that define the intestine is not established. Therefore, HT29 (low-mucus producing) and its sub -population HT29-MTX (high-mucus producing) monoculture cells have been chosen in various investigations to study the role of mucus in bacterial adhesion and invasion. However, employing monoculture as a model to study how foodborne pathogens cross the intestinal barrier faces significant challenges in mimicking the complexity of intact threedimensional (3D) in vivo conditions. To address this issue, 3D co-culture models of the human intestine have been established as an alternative to the monoculture epithelial cells, allowing more accurate prediction of adhesion/invasion mechanisms. Thus, this article reviewed the role of mucus in adhesion/invasion studies of foodborne pathogens and discusses how the employment of diverse in vitro models impacts the properties of hostpathogen interactions.