Enteroaggregative Escherichia coli (EAEC) Strain in a Novel Weaned Mouse Model: Exacerbation by Malnutrition, Biofilm as a Virulence Factor, and Treatment by Nitazoxanide

Enteroaggregative Escherichia coli (EAEC) is increasingly recognized as a common cause of diarrhea in healthy, malnourished, and immune-deficient adults and children. There is no reproducible non-neonatal animal model for longitudinal studies of disease mechanism or therapy. Using two strains of human-derived EAEC to challenge weaned C57BL/6 mice, we explored an in vivo model in mice of EAEC infection, in which disease was monitored quantitatively as growth rate, stool shedding, and tissue burden of organisms; nutritional status was varied; and a new class of therapeutics was assessed. A single oral challenge of enteroaggregative E. coli (EAEC) strain 042 resulted in significant growth shortfalls (5-8 % of body weight in 12 days), persistent shedding of microorganisms in stool (>103.2 cfu/10mg of stool for 2+ weeks), and intestinal tissue burden (~103 cfu/10mg of tissue detectable up to 14 days post-challenge). Moderate malnourishment of mice using a ‘regional basic diet’, containing 7% protein and reduced fat and micronutrients, heightened all parameters of infection. Nitazoxanide in sub-MIC doses, administered for three days at the time of EAEC challenge, lessened growth shortfalls (by > 10 % of body weight), stool shedding, (by 2-3 logs/10mg of stool) and tissue burden of organisms (by > 75% in jejunum and colon). The weaned C57BL/6 mouse challenged with EAEC is a convenient, readily inducible model of EAEC infection with three highly quantifiable outcomes, and in which disease severity is highly dependent on nutritional status of the host and modifiable in the presence of inhibitors of pyruvate ferredoxin oxidoreductase such as Nitazoxanide.