LAUSR

BACKGROUND AND AIMS There is debate whether atypical enteropathogenic E. coli (aEPEC) causes disease in adults. aEPEC is commonly detected in symptomatic and asymptomatic individuals. aEPEC, in contrast to typical EPEC, lacks bundle forming pili, altering its pathogenicity. Here we define for the first time the clinical manifestations of sporadic aEPEC infection in US children and adults and determine if EPEC load correlates with disease. METHODS This is a retrospective case-control study of 380 in/out-patients of all ages. EPEC load in stools was determined by quantitative PCR. RESULTS Diarrhea, vomiting, abdominal pain, and fever were more prevalent in EPEC-positive cases than in EPEC-negative controls. aEPEC infection caused mostly acute, mild diarrhea lasting for 6-13 days. However, some had severe diarrhea with 10-40 BMs/day or had persistent/chronic diarrhea. Fever, vomiting, and abnormal serum sodium levels were more common in children. Adults more often reported abdominal pain and longer duration of diarrhea. Symptomatic aEPEC infection was associated with leukocytosis in 24% of cases. EPEC load >0.1% was associated with symptomatic infection, however, loads varied greatly. Co-infecting pathogens did not alter diarrhea severity or EPEC load. Longitudinal data reveal that some are colonized for months to years, or repeatedly infected. CONCLUSIONS AEPEC is associated with a wide array of symptoms in adults ranging from asymptomatic carriage to severe diarrhea. Higher EPEC loads are associated with presence of symptoms, but bacterial load does not predict disease or severity. Future studies are needed to understand bacterial and host factors that contribute to aEPEC pathogenicity to improve diagnostic tools and clinical care.