Enteroaggregative Escherichia coli virulence markers: positive association with distinct clinical characteristics and segregation into 3 enteropathogenic E. coli serogroups.

BACKGROUND Enteroaggregative Escherichia coli (EAEC) are a heterogeneous category of emerging pathogens associated with acute and persistent diarrhea. METHODS We performed a case-control study to evaluate the association of EAEC strains and their virulence markers with infantile diarrhea in Brasilia, Brazil. RESULTS Of the EAEC markers that were tested, only EAEC heat-stable toxin (EAST1), protein involved in colonization (Pic), and the CVD432 sequence showed positive correlation with diarrhea; however, these virulence traits presented associations with distinct clinical characteristics. Although CVD432-positive strains were associated with persistent diarrhea, EAST1-positive strains were statistically correlated with acute diarrhea only in children >6 months of age. Typical EAEC strains were found with equal frequency in case patients and control subjects. O antigens of enteropathogenic E. coli (EPEC) were also sought, and the data showed that the EAEC markers are frequently segregated into 3 EPEC serogroups: O126, O128, and O158. CONCLUSIONS The presence of EPEC O antigens along with EAEC markers influenced the positive association of E. coli strains with diarrhea. Concerning the detection of the AA phenotype, the CVD432 sequence presented a low positive predictive value, regardless of its high specificity as a marker.