Isolation, Extraction, and Characterization of Verotoxin-producing Escherichia coli O157:H7 from Diarrheal Stool Samples

Background: Escherichia coli O157:H7 infection causes hemorrhagic colitis and is diagnosed based on symptoms such as cramps, stomach pain, and watery diarrhea. Shiga-like toxins (Verotoxin) produced by Escherichia coli O157:H7 damages endothelial cells of both kidney and brain, causing renal dysfunction and neurological problems. Methods: The present study focuses on identifying the prevalence of Verotoxin-producing Escherichia coli O157:H7 among diarrheal inpatients at Erode Government Hospital, India, and its antibiogram. Further, the Verotoxins were characterized by using SDS-PAGE analysis. A total of 123 samples were collected both from diarrheal stools, and strains from 37 samples (43.02 %) were found to have the presence of E. coli.  The organisms were identified based on their colony morphology on various media, cell morphology, and biochemical tests. The Shiga-like toxin production was identified by non-fermentation of sorbitol on SMAC agar plates. Confirmation of Shiga-like toxin was performed using agglutination assay.  Results: In total, 12 isolates showed agglutination and these isolates were confirmed to be E. coli O157:H7. The molecular weight of the Verotoxin was found to be between 20 and 29 kD. The antibiogram profile of the four isolated strains against 10 standard antibiotics was determined. Conclusion: The results of this study show the occurrence of drug resistance on hemorrhagic colitis causing E. coli O157:H7.