en Epidemiologic studies including microbial genotyping, phenotyping and serotyping Epidemiologic studies including microbial genotyping, phenotyping and serotyping Original article Original article <span style="font-size:11pt"><span style="line-height:normal"><span sans-serif="" style="font-family:Calibri,"><b><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">Introduction</span></span></b><span style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">: Diarrheal disease is a major cause of morbidity and mortality among children under the age of 10 worldwide, particularly in low- and middle-income countries. Diarrheagenic <i>Escherichia coli</i> (DEC) is a common cause of gastroenteritis in children. This study investigated the frequency, virulence markers, and antibiotic resistance patterns of DEC in children below 10 years with acute diarrhea in Zahedan, Iran. <b>Methods</b>: In this cross-sectional study, 300 <i>E. coli</i> isolates were collected from stool samples of children aged below 10 years with diarrhea who presented to hospitals and clinical laboratories in Zahedan. DEC pathotypes were identified using multiplex PCR and confirmed by standard biochemical tests and polyvalent antisera. <b>Results</b>: Of the 300 <i>E. coli</i> isolates examined, 89 (29.6%) were identified as diarrheagenic <i>E. coli</i> (DEC) using polyvalent antisera targeting known DEC pathotypes. Enteroaggregative <i>E. coli</i> (EAEC) was identified in 31 isolates (34.83%) based on reaction with antiserum No. 1. Enterotoxigenic <i>E. coli</i> (ETEC) was identified in 35 isolates (39.33%) based on reaction with antiserum No. 2. Enteropathogenic <i>E. coli</i> (EPEC) was identified in 23 isolates (25.84%) based on reaction with antiserum No. 3 (anti-coli3). Multiplex PCR identified the most common pathotype as EAEC (37.6%), followed by EPEC (21.7%), ETEC (15.9%), and EIEC (11.5%). Statistical analysis revealed no significant correlation between the presence of specific virulence genes (<i>e.g.</i>, <i>eae</i>, <i>pcvd432</i>, <i>elt</i>, <i>est</i>, and <i>iaH</i>) and antibiotic resistance patterns in the DEC isolates. <b>Conclusion</b>: Given the distribution of DEC pathotypes among children in Zahedan and their increased antibiotic resistance, antibiotic treatment should be guided by molecular typing and antimicrobial susceptibility testing of isolates, when appropriate. </span></span></span></span></span> Diarrheagenic E. coli (DEC), Antibiotic resistance, Enteroaggregative E. coli (EAEC), Children, Zahedan, Multiplex PCR 59 66 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-483-1&slc_lang=en&sid=1 Mojdeh Jahantigh mojde_jahan@yahoo.com 0000-0001-7381-5882 Yes Infectious Diseases and Tropical Medicine Research Center, Research Institute of Cellular and Molecular Sciences in Infectious Diseases, Zahedan University of Medical Sciences, Zahedan, Iran Nasrin Seyedzayi nasrinsayadzayi@gamil.com 0009-0007-1797-7503 No Department of Microbiology, Zahedan University of Medical Sciences, Zahedan, Iran