Isolation of shiga toxin producing Escherichia coli O157:H7 from Bovine samples of Dhaka, Bangladesh

Abstract

Shiga toxin producing Escherichia coli (STEC) have recently emerged as important food-borne pathogens especially serotype O157:H7. Human diseases ranging from mild diarrhea to hemorrhagic colitis, hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura can be caused by STEC, typically affecting children, elderly and immune-compromised patients. Bangladesh is considered as an endemic area for shiga toxin producing E.coli O157:H7. The study is conducted to isolate E.coli from bovine samples followed by genotyping identification using PCR. For this purpose bovine feces were collected around Dhaka city to isolate E. coli. The samples were first enriched in enrichment broth and then plated onto MacConkey agar. A total of 61 isolates from 7 samples were presumptively selected as E. coli from primary MacConkey plate. The isolates were subjected to detailed biochemical characterizations using Eosin Methylene Blue (EMB) agar medium, Indole production test, Methyl-red test, Voges-Proskauer’s test, Citrate utilization test, Triple Sugar Iron test and fermentation test. Out of 35 samples analyzed, only 22 isolates, gave identical biochemical properties compared to a reference E. coli strain. Culturally and biochemically positive isolates were tested for stx1 and stx2 genes. From all these isolates, no stx1 gene was detected but 3 were detected for stx2. Therefore, this data showed the prevalence of E. coli in Bangladesh and demands for further study for the prevention of diseases.