Mucin Increases the Virulence of Enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is an important pathogen of humans and other mammals (such as piglets and calves). Mucin, a glycoprotein that forms the major fraction of the intestinal mucus layer, is a key host substance that ETEC encounters in the host environment. This study investigated whether physiologically relevant concentrations of mucin modulate virulence-related phenotypes in ETEC. Growth of ETEC remained unaffected across mucin concentrations ranging from 50 mg/L to 1000 mg/L. Mucin increased swimming motility in a concentration-dependent manner, with motility doubling at the highest concentrations tested relative to the mucin-free control. Further, mucin also increased biofilm formation in a dose-dependent manner, with approximately 4.5-fold higher biofilm levels at the highest concentration. Finally, mucin increased the virulence of ETEC in the invertebrate infection model Galleria mellonella, resulting in a 1.5- to 3.3-fold increase in larval mortality caused by mucin-treated ETEC compared with the untreated ETEC group. These findings indicate that ETEC responds to mucin as a host-derived cue, promoting virulence-associated traits linked to colonization and infection. Understanding this host-pathogen interaction may lead to the development of novel control strategies against ETEC, which is an urgent societal challenge in the context of rising antibiotic resistance.