Escherichia coli: Origins, Pathogenesis, and Epidemiology

Theodore von Escherich

German pediatrician; described E. coli in 1884.

Bacterium coli commune

Original name for E. coli by Escherich.

Typhoid fever

Pathological disease caused by E. coli.

Taxonomy of Escherichia

Includes at least 8 species related to Shigella.

Morphology of E. coli

Bacilli shape; gram-negative; mostly motile.

Peritrichous flagella

Flagella arrangement in E. coli for motility.

Epidemiology of E. coli

Responsible for 111 million gastroenteritis cases yearly.

Global UTI cases

E. coli causes 140 million UTIs annually.

Shigellosis

Accounts for 180-190 million cases yearly.

Reservoirs for E. coli

Found in ungulates, humans, and environment.

Human carriage rates

E. coli colonizes human intestines at 100%.

Zoonotic E. coli

Pathogenic strains acquired from animal reservoirs.

Acid tolerance

E. coli survives stomach acidity, pH 1-4.

Acid fitness island (AFI)

12 kb gene cassette for acid tolerance.

Gad system

Includes GadA, GadC, and GadE for acid tolerance.

ID50 of E. coli

Infectious dose is 10-100 CFU.

Adherence factors

E. coli uses fimbriae to colonize tissues.

Type I fimbriae

Colonizes oropharyngeal and intestinal tissues.

P-fimbriae

Binds receptors in urinary tract for colonization.

Uropathogenic E. coli (UPEC)

Responsible for 80% of community-acquired UTIs.

Enterohemorrhagic E. coli (EHEC)

Emerging pathogen causing hemorrhagic colitis.

Toxin-mediated hemolytic uremic syndrome (HUS)

Severe complication from EHEC infection.

Type III secretion system (T3S)

Transports virulence factors into host tissues.

Locus of enterocyte effacement (LEE)

Pathogenicity island encoding EHEC T3S genes.

Pedestal lesions

Formed by EHEC colonization using T3S.

Intimin

Adherence factor interacting with Tir in EHEC.

Tir

Translocated receptor for EHEC adherence.

T3S

Type III secretion system for injecting virulence factors.

Pedestal

Actin-rich structure formed beneath EHEC.

AE lesions

Attaching and effacing lesions damaging intestinal barrier.

EHEC

Enterohemorrhagic E. coli causing severe intestinal disease.

Shiga toxin

Cytotoxin produced by EHEC and Shigella dysenteriae.

AB class toxin

Toxin with A and B subunits affecting cells.

28S rRNA

Target of Shiga toxin for protein synthesis inhibition.

Receptor-mediated endocytosis

Cellular uptake via receptor binding.

Cellular trafficking

Movement of substances within cells.

IpaB

Effector protein that destroys macrophages.

Invasins

Virulence factors promoting intracellular invasion.

The Zipper mechanism

Invasion via external receptor interaction.

The Trigger mechanism

Invasion triggered by secreted effectors.

Phagosome

Membrane-bound vacuole containing engulfed pathogens.

pINV plasmid

Plasmid essential for Shigella pathogenesis.

SHI

Pathogenicity island in Shigella's pINV plasmid.

VirG

T3S protein recruiting host actin for invasion.

MacConkey Agar

Selective medium differentiating lactose fermenters.

SMAC plates

Differential medium for EHEC serotype O157:H7.

Hemolytic Uremic Syndrome (HUS)

Serious complication from EHEC infection.

Doxycycline

Antibiotic sometimes used for diarrheagenic infections.

Trimethoprim (TMP)

First-line antibiotic for UTIs.

Ciprofloxacin

Fluoroquinolone antibiotic for bacterial infections.

Lateral propagation

Invasion of adjacent cells by replicating pathogens.

Endosome

Vesicle formed during endocytosis.

Caspase-dependent cell death

Programmed cell death activated by IpaB.

Food safety measures

Practices to prevent foodborne infections.

Immunoassays

Tests detecting specific antigens or antibodies.

PCR for Shiga toxin

Molecular method for detecting STX presence.

EHEC O157:H7

Serotype of E. coli lacking sorbitol fermentation.