Molecular Detection of Diffusely Adherent Escherichia coli Strains Associated with Diarrhea in Shiraz, Iran

Abstract

Background: Diarrhea continues to be one of the most common causes of morbidity and mortality among children in developing countries. Recently, some studies have implicated diffusely adherent Escherichia coli (DAEC) strains as a cause of diarrhea. The clinical manifestations of diarrhea caused by DAEC strains may include watery or bloody diarrhea, abdominal pain, dehydration, and fever. Objectives: The aims of this study were (1) isolation of E. coli from fecal samples obtained from patients with diarrhea in Shiraz (Iran), (2) detection of DAEC pathotypes in isolates by molecular diagnostic techniques such as conventional PCR and real-time PCR assays, and (3) investigation of the antibiotic susceptibility of DAEC isolates. Materials and Methods: Seven hundred and fifteen stool specimens of diarrhea patients were collected in Shiraz, Fars, Iran. Diarrheagenic E. coli strains were isolated by standard biochemical analysis. Susceptibility testing was performed by the diffusion method, according to the guidelines of the Clinical and Laboratory Standards Institute. Real-time PCR and conventional PCR were used to detect the daaD gene in the DAEC strains isolated. Results: Of the 715 stool samples tested, 101 (14.1%) were identified as E. coli by biochemical tests and culture. Of the infected patients, 58 (57%) were male and 43 (43%) were female, with a mean age of 13.52 (SD, 1.66) years. Eight of the E. coli strains were identified as DAEC strains. The most effective antibiotics against the DAEC isolated were levofloxacin and imipenem, and the least effective antibiotics were ampicillin and penicillin. Conclusions: Our analysis indicated that DAEC strains may be considered as potential pathogens in Shiraz, southern Iran. Further, although the prevalence of DAEC is low, prevention of infection caused by this bacterium among asymptomatic patients is crucial. Therefore, further characterization of the different virulence aspects of DAEC strains is required.