Enteroinvasive E. coli (EIEC): Characteristics, Pathogenesis, Diarrhea & Diagnosis

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  • Enteroinvasive E. coli (EIEC) strains are rare in both developed and developing countries.
  • EIEC infections are characterized by a period of watery diarrhea that precedes the onset of scanty dysenteric stools containing blood and mucus.
  • Pathogenic strains are primarily associated with a few restricted O serotypes: O124, O143, and O164.
  • EIEC strains are biochemically, genetically, and pathogenetically related closely to Shigella spp.
Enteroinvasive E. coli (EIEC)

Disease Caused

  • It causes ulceration of the bowel, dysentery (diarrhea with mucus and blood, called bacillary dysentery resembling Shigellosis).

Mode of Transmission

  • EIEC outbreaks are usually foodborne or waterborne, although person-to-person transmission does occur.  
  • The infective dose of EIEC in volunteers is higher than that for Shigella spp. and thus the potential for person-to-person transmission is lessened. 

Pathogenesis of Enteroinvasive E. coli (EIEC)

EIEC pathogenesis comprises

  1. epithelial cell penetration,
  2. lysis of the endocytic vacuole,
  3. intracellular multiplication,
  4. directional movement through the cytoplasm, and
  5. extension into adjacent epithelial cells 
  • EIEC is not toxigenic, but invasive.
  • A series of genes on a plasmid mediates bacterial invasion (pInv genes) into the colonic epithelium. The epithelial cell invasion is most importantly mediated by a plasmid-coded antigen called virulence marker antigen (VMA).
  • The bacteria then lyse the phagocytic vacuole and replicate in the cell cytoplasm.
  • Movement within the cytoplasm and into adjacent epithelial cells is regulated by formation of actin tails (similar to that observed with Listeria).
  • This process of epithelial cell destruction with inflammatory infiltration can progress to colonic ulceration.

Clinical Features

  • The bacteria are able to invade and destroy the colonic epithelium, producing a disease characterized initially by watery diarrhea.
  • A minority of patients progress to the dysenteric form of the disease, consisting of fever, chills, malaise, abdominal cramps, and blood and leukocytes in stool specimens.

Diagnosis

EIEC strains can be difficult to distinguish from Shigella spp and from other E. coli strains, including nonpathogenic strains. In general, identification of EIEC entails demonstrating that the organism possesses the biochemical profile of E. coli, yet with the genotypic or phenotypic characteristics of Shigella spp.

  • Detection of VMA by ELISA
  • HeLa cell invasion assay
  • Sereny test (inoculation of bacterial suspension into guinea pig eyes produces conjunctivitis)
  • Compared with other E. coli strains, EIEC are biochemically atypical being non-motile, lactose non· fermenters and negative for lysine decarboxylase.

Treatment

  • Patients with profuse diarrhea or vomiting should be rehydrated. 
  • Antibiotics to treat non-STEC diarrheagenic E. coli include fluoroquinolones such as ciprofloxacin, macrolides such as azithromycin, and rifaximin.

References

  1. Murray, P. R., Rosenthal, K. S., & Pfaller, M. A. (2013). Medical microbiology. Philadelphia: Elsevier/Saunders
  2. Parija S.C. (2012). Textbook of Microbiology & Immunology.(2 ed.). India: Elsevier India.
  3. Sastry A.S. & Bhat S.K. (2016). Essentials of Medical Microbiology. New Delhi : Jaypee Brothers Medical Publishers.
  4. https://cmr.asm.org/content/11/1/142
  5. https://www.amboss.com/us/knowledge/Diarrheagenic_E._coli
  6. https://www.ncbi.nlm.nih.gov/pubmed/7546449
  7. https://wwwnc.cdc.gov/eid/article/22/7/15-2080_article
  8. https://wwwnc.cdc.gov/travel/yellowbook/2018/infectious-diseases-related-to-travel/escherichia-coli-diarrheagenic

About Author

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Sagar Aryal, PhD

Dr. Sagar Aryal is a microbiologist, researcher, and science communicator from Nepal. He is also co-founder and Research Head of the Department of Natural Products at the Kathmandu Research Institute for Biological Sciences (KRIBS), where he leads research on natural product discovery and microbial biodiversity. Dr. Aryal earned his Ph.D. in Microbiology from Tribhuvan University, Kathmandu, Nepal, in 2025, supported by a DAAD Research Grant and a University Grants Commission (UGC) Nepal Ph.D. Fellowship. His research interests include Actinomycetes, Myxobacteria, microbial taxonomy, and natural products, particularly the discovery of bioactive compounds with potential pharmaceutical applications. He isolated and identified Nocardia nepalensis, a novel bacterial species from Nepal, contributing to understanding microbial diversity in the region. Dr. Aryal has published more than 16 research articles in international journals and contributed three book chapters to established academic publications. He has presented scientific research findings and developed international research collaborations through visits to more than 18 countries across Asia, Europe, North America, and Oceania. From 2023 to 2025, he served as the American Society for Microbiology (ASM) Young Ambassador to Nepal. Since December 2025, he has served as an Editorial Board Member of Scientific Reports, a Nature Portfolio journal. In recognition of his scientific contributions, Dr. Aryal received the NAST Science and Technology Youth Award 2025 from the Nepal Academy of Science and Technology. He previously received the Frs. Locke and Stiller Research Award (LSRA) for the 2017-2018 cycle from St. Xavier's College, Kathmandu, and a Nepal Academy of Science and Technology (NAST) Research Grant for 2017-2018. Alongside his scientific career, Dr. Aryal has more than 15 years of experience in blogging, content writing, and search engine optimization (SEO).