Which E. coli pathotype is characterized by attachment and effacement without toxin production?

Which E. coli pathotype is characterized by attachment and effacement without toxin production?

• A. EHEC
• B. ETEC
• C. EAEC
• D. EPEC

Answer: (D)

The main idea tested is identifying the E. coli pathotype defined by attaching to enterocytes and causing effacement of microvilli without producing toxins. This pattern is characteristic of Enteropathogenic E. coli (EPEC). EPEC uses a type III secretion system to inject Tir into the host cell, Tir integrates into the membrane and binds the bacterial intimin, triggering rearrangements that remove the microvilli and create attaching and effacing lesions. Because there’s no toxin produced by this pathotype, disease arises from the intimate adherence and the disruption of the intestinal surface rather than toxin-mediated secretion or damage. In contrast, the other pathotypes involve toxin production or different adherence patterns: EHEC produces Shiga toxin (and can form A/E lesions but toxin is a key feature), ETEC causes secretory diarrhea via enterotoxins, and EAEC shows a stacked-brick adherence pattern with biofilm formation rather than the A/E lesions seen with EPEC.

The main idea tested is identifying the E. coli pathotype defined by attaching to enterocytes and causing effacement of microvilli without producing toxins. This pattern is characteristic of Enteropathogenic E. coli (EPEC). EPEC uses a type III secretion system to inject Tir into the host cell, Tir integrates into the membrane and binds the bacterial intimin, triggering rearrangements that remove the microvilli and create attaching and effacing lesions. Because there’s no toxin produced by this pathotype, disease arises from the intimate adherence and the disruption of the intestinal surface rather than toxin-mediated secretion or damage. In contrast, the other pathotypes involve toxin production or different adherence patterns: EHEC produces Shiga toxin (and can form A/E lesions but toxin is a key feature), ETEC causes secretory diarrhea via enterotoxins, and EAEC shows a stacked-brick adherence pattern with biofilm formation rather than the A/E lesions seen with EPEC.