iarjhcpIARJHCPIARJHCP2789-6048https://doi.org/10.47310/iarjhcp.2025.v05i02.004Impact of Enteropathogenic Escherichia coli (EPEC) on ZO-1 and IL-8 Gene Expression in Intestinal Epithelial Cells of Pediatric Patients with Diarrhea in IraqGhanim A.AbbasSalah KareemSafi AlkhalidiPolytechnic College/Al–Qadisiyah, Al-Furat Al-Awsat Technical University, IraqBackground: Enteropathogenic Escherichia coli (EPEC) is a leading cause of childhood diarrhea in developing countries. This study aimed to investigate the clinical characteristics and molecular mechanisms of EPEC-induced diarrhea in children, with particular focus on intestinal barrier function and inflammatory response. Methods: A case-control study was conducted involving 120 children with diarrhea and 40 healthy controls. EPEC detection was performed using polymerase chain reaction. Clinical parameters including diarrhea type, duration, frequency and dehydration status were assessed. Intestinal biopsy samples were analyzed for tight junction protein ZO-1 and inflammatory marker IL-8 expression using quantitative real-time PCR. Statistical analyses included Chi-square tests, t-tests, Mann-Whitney U tests and Pearson correlation analysis. Results: EPEC was detected in 35 of 120 (29.2%) children with diarrhea. EPEC-positive children showed significantly different clinical presentations compared to EPEC-negative cases, including predominant watery diarrhea (71.4% vs 56.5%, p = 0.037), longer duration (median 7 vs 4 days, p<0.001), higher frequency (median 7 vs 5 episodes/day, p = 0.003) and more severe dehydration (17.1% vs 4.7% with severe dehydration, p = 0.014). Molecular analysis revealed significant intestinal barrier dysfunction in EPEC-positive patients, with reduced ZO-1 expression (0.42±0.15 vs 1.00±0.00 fold change, p<0.001) and elevated IL-8 expression (5.60±1.70 vs 1.00±0.00 fold change, p<0.001) compared to controls. Typical EPEC (eae+/bfp+) caused more severe molecular alterations than atypical EPEC (eae+/bfp). Strong correlations were observed between molecular markers and clinical severity: ZO-1 expression negatively correlated with diarrhea duration (r = -0.67, p<0.001) and frequency (r = -0.59, p<0.001), while IL-8 expression showed positive correlations with these parameters (r = 0.62 and r = 0.54, respectively, p≤0.001). Conclusion: EPEC infection in children is associated with distinctive clinical features including prolonged watery diarrhea and severe dehydration. The study demonstrates that EPEC-induced intestinal barrier dysfunction and inflammation directly correlate with clinical disease severity, providing mechanistic insight into EPEC pathogenesis. Typical EPEC strains cause more severe molecular and clinical manifestations than atypical strains. These findings highlight the importance of early EPEC detection and may inform targeted therapeutic approaches for childhood diarrhea.