Antibiotic resistance pattern and molecular characterization of extended-spectrum β-lactamase producing enteroaggregative Escherichia coli isolates in children from southwest Iran

Introduction: Enteroaggregative Escherichia coli (EAEC) has been implicated as an emerging cause of traveler's diarrhea, persistent diarrhea among children, and immunocompromised patients. The present study aimed to investigate the prevalence of antibiotic resistance, extended-spectrum beta-lactamase (ESBL) production, and virulence factors of EAEC isolates obtained from Iranian children suffered from diarrhea. Materials and methods: In this cross-sectional study, from March 2015 to February 2016, 32 EAEC isolates were collected from fecal samples of children aged < 12 years with diarrhea in southwest of Iran. All EAEC isolates identified using phenotypic and molecular methods and the cell line adhesion assay. Antimicrobial susceptibility testing was determined using disk diffusion method. The presence of virulence factors and ESBL resistance genes were determined by polymerase chain reaction. Results: Overall, 28.1% (9/32) of the isolates were positive for at least one of virulence genes. The most frequent gene was aap with a frequency of 96.9%. Neither aafA nor aggA gene was detected among all of the EAEC isolates. Antimicrobial susceptibility testing revealed the highest resistance rate to ampicillin (100%) and co-trimoxazole (100%), followed by ceftriaxone (81.3%). Further analysis revealed that the rate of ESBLs-producing isolates was 71.9% (23/32). Polymerase chain reaction screening revealed that 87.5% and 65.5% of EAEC isolates were positive for bla(TEM) and bla(CTX-M) genes, respectively, and 17 (53.1%) of isolates contained both bla(TEM) and bla(CTX-M) genes. Conclusion: The high detection rate of ESBL-producing EAEC isolates accompanied with virulence genes highlights a need to restrict infection control policies in order to prevent further dissemination of the resistant and virulent EAEC strains.