Entero-invasive E. coli (EIEC) and Shigella are clinically and microbiologically similar. The key microbiological distinction between them is:

• A EIEC produces Shiga toxin, Shigella does not
• B EIEC is lysine decarboxylase positive, Shigella is lysine decarboxylase negative; EIEC is also non-motile and late lactose fermentor ✓
• C Shigella is motile and EIEC is non-motile — no other distinction exists
• D EIEC exclusively infects the colon; Shigella uniquely infects the small intestine

Explanation

Both EIEC and Shigella invade colonic epithelial cells using an invasion plasmid antigen (ipa) locus and produce dysenteric illness, but can be distinguished biochemically: EIEC is lysine decarboxylase (LDC) positive (or variable), and is a late lactose fermenter; Shigella is consistently LDC negative (except S. sonnei which is LDC variable), non-motile, and non-lactose fermenting. Both are non-motile. EIEC does not produce Shiga toxin (that is EHEC/S. dysenteriae type 1). Clinical and epidemiological overlap is significant, and whole-genome sequencing confirms they occupy a phylogenetic continuum.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.