Risk of Shiga Toxin-Producing Escherichia coli Infection in Humans Due to Consuming Unpasteurized Dairy Products

Background: Cattle transiently harbor Shiga-toxigenic Escherichia coli (STEC) in their gastrointestinal tracts, and many human infections result from ingestion of contaminated dairy products. The occurrence of STEC infections in human ranges from mild watery diarrhea to life-threatening conditions such as thrombotic thrombocytopenic purpura, hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS). Objective: Isolation of STEC from unpasteurized dairy products as a source of human infections is the aim of this research. Materials and Methods: In this study, after collecting 150 samples of unpasteurized dairy products from different parts of Ahvaz, primary enrichment, selective enrichment and conventional biochemical tests were done and the suspected DNA isolates were extracted by boiling. Confirmation of being toxigenic isolates was performed by multiplex polymerase chain reaction (mPCR) assay. The stx1- and stx2-specific primers were used in m-PCR. Results: Out of 75 isolates with lactose-fermentation ability, 11 E. coli strains were confirmed by biochemical tests. Two isolates (18.18%) were detected as carriers of stx2 gene by PCR. Conclusion: Because of low infective dose, the presence of a low percentage of toxigenic E. coli in dairy products could be a grand public health risk, while the bacteria other than E. coli could be producing Shiga toxin which should not be ignored.