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.