Adherence properties and adhesin-encoding genes detected in enteroaggregative <i>Escherichia coli</i> (EAEC)

Enteroaggregative <i>Escherichia coli</i> (EAEC) is a major cause of both acute and persistent diarrhea worldwide, with a particularly high prevalence in developing countries. In this study, we performed a comprehensive molecular and phenotypic characterization of 140 EAEC isolates obtained from both pediatric and adult patients with diarrheal disease. Our findings support the knowledge that EAEC represents a heterogeneous group of isolates that have emerged from distinct <i>E. coli</i> genetic backgrounds, primarily within phylogroups A, B1, and D. Although most isolates exhibited the characteristic aggregative adherence (AA) pattern on infected epithelial cells, a subset displayed the chain-like adherence (CLA) phenotype and carried the <i>aatA</i>, <i>aggR</i>, and <i>agg4A</i> genes. This scenario highlights the need for continuous surveillance to monitor the emergence of novel virulence strategies employed by EAEC to adhere to host cells and cause disease.