E. coli and Associated Diarrheal Diseases

E. coli

• Gram negative, enterobacteria

• Common resident of mucosal layer of gut; most strains are commensal

• Several strain cause diarrhea, hemolytic uremic syndrome, urinary tract infections, meningitis, sepsis

EHEC

Enterohemorrhagic strain causing bloody diarrhea.

ETEC

Enterotoxigenic strain causing watery diarrhea.

EPEC

Enteropathogenic strain linked to diarrhea outbreaks.

EAEC

Enteroaggregative strain causing persistent diarrhea.

DAEC

Diffusely adhering strain causing infant diarrhea

EIEC

Enteroinvasive strain causing dysentery symptoms.

UPEC

Uropathogenic strain causing urinary tract infections.

MNEC

Meningitis-associated strain causing sepsis.

Attaching and effacing

• EPEC and EHEC

• Attach to epithelial cells

• Type III secretion system injects in effectors

• Actin cytoskeleton rearranged

• Polymerized actin underneath bacteria

Type III secretion system

Injects effectors into host cells.

EPEC and diarrhea

• Effacement of enterocytes– loss of absorbant surface

• Disruption of tight junctions– Esp proteins

• Induction of IL-8; neutrophil recruitment and inflammation

  • Changes ability of gut to absorb moisture

  • Can lead to destruction of enterocytes

Shiga toxin (Stx)

Toxin causing cell death via rRNA cleavage.

• B subunit binds specific receptors (Gb3) on enterocytes and renal cells

• A subunit enters cells

• A cleaves rRNA

• Translation ceases

• Cells die

Hemolytic Uremic Syndrome

• RBC damage– anemia

• Loss of platelets

• Bloody diarrhea

• Kidney damage

• Liver damage

LT

• heat labile enterotoxin

  • ADP ribosylates stimulatory G protein for adenylate cyclase

  • Increases cAMP

ST

• heat stable enterotoxin

  • Binds guanylate cyclase; increases cGMP

EAEC work by

• Form biofilms on surface of cells

• Activate IL-8; chemotaxis and inflammation

• Pet– disturbs actin cytoskeleton; kills cells

UPEC

• Distinct fimbriae– type I and Pap
• Internalized bacteria colonies
• Hemolysin; causes apoptosis of cells
• Sat– vacuoles in cells, death of cells

Hemolysin

UPEC toxin causing apoptosis in host cells.

Esp proteins

Disrupt tight junctions in enterocytes.

IL-8

Cytokine inducing neutrophil recruitment and inflammation.

Actin cytoskeleton rearrangement

Process altered by EPEC and EHEC attachment.

cAMP

Cyclic AMP, a secondary messenger in cells.

cGMP

Cyclic GMP, involved in signaling pathways