Dietary Factors in Prevention of Pediatric Escherichia coli Infection: A Model Using Domestic Piglets. 
Enterotoxigenic Escherichia coli (ETEC) is the major etiological agent causing acute watery diarrhea that is most frequently seen in young children in lower-income countries.  The duration of diarrheal symptom may be shortened by antibiotic treatment, but ETEC is relative refractory to common antibiotics.  Burgeoning evidence suggests bioactive components that naturally occur in human milk (e.g., lysozyme and oligosaccharides) and plants (e.g., nondigestible carbohydrates and phytochemicals) contain antimicrobial functions are promising preventive measures to control ETEC infection.  Although the exact protective mechanisms may vary for each compound and are still not completely understood, they generally act to (1) competitively inhibit the binding of pathogenic bacteria and toxins to gut epithelium; (2) directly kill pathogens; and (3) stimulate and/or enhance host mucosal and systemic immune defense against pathogenic microorganisms.  An appropriate ETEC-challenge animal model is critical to evaluate the effect and unveil the mechanism of bioactive compounds in prevention of enteric infection.  Despite wide application in biomedical research, rodents do not usually manifest typical clinical signs of enteric infections.  The remarkable differences in digestive physiology, immune response, and gut microbiota between rodents and human beings necessitate the use of alternative animal models.  Pigs are closely related to humans in terms of genomes, physiology, anatomy of gastrointestinal tracts, digestive enzymes, components of immune system, and gut microbiota.  Like human infants and young children, nursing and nursery piglets are more susceptible to ETEC infection and reproduce the clinical signs as observed in humans.  Hence, the ETEC-challenge piglet represents a valuable translational model to study pathogenesis and evaluate dietary factors (e.g., milk bioactive compounds, nondigestible carbohydrates, and phytochemicals) as preventive measures for ETEC infection in pediatrics.