How does Escherichia coli O157:H7 differ from non-pathogenic E. coli?

• A. It is resistant to all antibiotics
• B. It produces Shiga toxin and can cause severe bloody diarrhea
• C. It has a longer incubation period
• D. It only causes mild food poisoning

Answer: (B)

Escherichia coli O157:H7 is a significant pathogenic strain of E. coli that stands out due to its ability to produce Shiga toxin, which is a key factor in its virulence. The presence of this toxin disrupts protein synthesis in human cells, leading to severe gastrointestinal symptoms, including bloody diarrhea. This strain is associated with serious complications, such as hemolytic uremic syndrome (HUS), which can lead to kidney failure.

In contrast, non-pathogenic strains of E. coli are part of the normal gut flora and do not produce harmful toxins. They typically do not cause severe illness and are beneficial in maintaining gut health.

Other aspects mentioned in the choices do not accurately describe the distinctions between E. coli O157:H7 and non-pathogenic variants. For instance, while antibiotic resistance can vary, claiming that O157:H7 is resistant to all antibiotics is not accurate. Additionally, the incubation period for O157:H7 does not significantly differ from that of non-pathogenic strains, and the pathogenic strain can cause more severe illness than just mild food poisoning, which further emphasizes the critical differences in pathogenic potential.