A 32-year-old man with HIV and CD4 count of 90 cells/µL has chronic watery diarrhea for six weeks. Stool culture grows E. coli that forms a stacked brick aggregative pattern of adherence on HEp-2 cell monolayers. Which diarrheagenic E. coli is identified?
- A Enteroinvasive E. coli (EIEC)
- B Enteropathogenic E. coli (EPEC)
- C Enteroaggregative E. coli (EAEC) ✓
- D Diffusely adherent E. coli (DAEC)
Correct answer: C. Enteroaggregative E. coli (EAEC)
Explanation
The stacked brick aggregative adherence pattern on HEp-2 cells is the defining phenotypic marker of enteroaggregative E. coli, regulated by the plasmid-encoded AggR transcription factor. EAEC causes persistent watery diarrhea in children in developing regions, travelers, and importantly immunocompromised adults such as patients with HIV and low CD4 counts, where it is a recognized cause of chronic diarrhea. EPEC shows localized adherence, DAEC diffuse adherence, and EIEC is non-adherent but invades colonic cells.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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