Escherichia coli Flashcards
Describe E.coli
Gram- rod, facultative anaerobe, oxidase negative; Ferments glucose and lactose
Discuss enterotoxigenic e. coli (ETEC).
Not usually invasive, causes cholera-like diarrhea. Colonizes small intestine by adhering to microvilli
What are ETEC’s virulence factors?
- Heat-liable toxin (LT)
2. Heat-stable toxin (ST)
Give an in depth description of ETEC’s LT-1
Almost identical to cholera toxin in both action and receptor binding; Also is a AB subunit toxin.
Give an in depth description of ETECs LT-2
Also resemble cholera toxin but not to the extent of LT-1; Associated with animal disease.
Give an in depth description of ETEC’s STa?
Cysteine rich peptide; Blocks guanylate cyclase in apical cell membrane. Causes an increase in cGMP leading to water loss.
Give an in depth description of ETECs STb?
Associated with animal disease; Causes increase in bicarbonate secretion, altering pH.
Describe Enteroinvasive E.coli (EIEC)
Much like shigella, strictly human pathogenic. Bloody and watery diarrhea; Contains same invasion proteins as shigella.
Describe Enteropathogenic E. coli (EPEC)
Produces characteristic attachment and effacing lesions; Extracellular.
What are EPECs virulence factors?
- Bundle-forming pili
- Intimin receptor
- EPEC (Type 3) secreted proteins
Give an in depth description of EPECs bundle forming pili.
Type 4 class pili. Mediates adherence to host cell; Allows microcolony formation
What are the 3 components of the Locus for enterocyte effacement?
Intimin, Tir, and Esp
What role does intimin play in EPECs virulence?
Binds Tir
What role does Tir play in EPECs virulence?
Receptor for intimin
What role does Esp play in EPECs virulence?
Activates signal transduction and actin rearrangements in the cell.
