Lecture 19 Pathogenic shigella and E coli Flashcards
What species are part of your normal flora of your stomach?
- E. coli non-pathogenic species
- Klebsiella
- Enterobacter
- Proteus
- Serratia
What is not part of the human flora?
- Salmonella
- Shigella
- Yer sinia
- Pathogenic E. coli
What type of diseases are caused by bacteria not part of the human flora.
•Cause a wide variety of disease •endotoxic shock, UTI, diarrhea, HUS
How is E. Coli identified,
- Gram negative
- Lactose fermentation.
- indole positive
- most are normal colonic flora
What are the type of diseases caused by E. coli?
- Urinary Tract Infection (UTI)
- Gastroenteritis
- Septicemia - usually following UTI or gastroenteritis
- Neonatal meningitis
What E. Coli infections are not caused by a person’s own flora?
gastroenteritis and neonatal meningitis
What plates can be used to identify E. Coli?
- CHROMagar
- MacConkey
What is unique about CHROMagar?
Has a unique specific metabolism for multiple organisms, can grow multiple organism on plate and identify the different types.
What is a common theme between pathogenic E. Coli?
-secretion and new DNA. Not normal flora. Uses different mechs to cause disease.
What are the surface structures of E. Coli?
- O antigen
- H antigen (flagella)
- BFP pili
- CFA pili
- Type 1 pili
- K antigen capsule
- P pili
What are BFP pili?
bundle forming pili: found in EPEC strains
What is CFA pili?
colonization factor antigen: pili used by ETEC strains for binding to host cells
What are type 1 pili?
common pili binds via FimA to mannose residues on epithelial cells
How does EPEC cause diarrheal disease?
BFP used to form cluster of cells, injects effector proteins, causes pedestal formation.
How does EHEC cause diarrhea?
causes pedestal formation and injects Stx-shiga toxin into the cells.
How does EHEC cause disease?
uses CFA pili to bind then secretes two types of enterotoxins: ST (heat stable) and LT (heat labile).
How does EAEC cause disease?
forms a biofilm on the surface of the cells, produces cytotoxins and enterotoxins to cause diarrhea.
How does EIEC cause diarrhea?
binds, then invades cells, then escapes into the cytoplasm. Similar to Shigella.
How does DAEC cause diarrhea?
binds as single cells.
What is UPEC E. Coli?
- Uropathogenic E.coli:
- causes most cases of Pyelonephritis (kidney infection)
- infection starts from spreading to colon to bladder
What makes UPEC so good at causing infection?
-P pili and FimH
What are some characteristics of ETEC?
- prevalent in developing world (traveler’s diarrhea and infantile diarrhea
- spread via food
- attacks small bowel causing watery diarrhea
- no histological or inflammatory changes to GI tract.
- treatment is hydration
What are the toxins produced by ETEC?
- LT - Heat Liable (similar to cholera) .
- ST - heat stable
What are characteristics of EPEC?
- Most prevalent in the developing world
- Attacks small bowel
- Causes severe watery diarrhea, nausea and vomiting, dehydration
- Treatment: hydration
- EPEC has been used to study the interaction of a bacterial pathogen with the host target cell
How does EPEC form a intimate attachment?
- adheres and injects EspA-needle complex
- Tir translocated to cytoplasm
- Tir appears on surface of cell
- intamin can bind to TIR
What are the characteristics of EHEC?
- possible deaths
- bloody diarrhea
- HUS Hemolytic Uremic Syndrome
- small number
- small number can cause infection
- can survive acidity in the stomach.
What are the two virulence factors of EHEC?
- adhesins to epithelial cells
2. Shiga like toxins
What is EHEC’s Shiga like toxins?
- encoded by bacteriophage
- blocks protein synthesis and lead to cell death in kidneys
- some brain damage
- Stx-1, stx-2
What is a common source of EHEC?
- in cattle, they are not affected by the toxin
Why don’t you use abx on EHEC?
-can become toxin bombs
What are the characteristics of EAEC?
- cause watery diarrhea
- attacks small bowel
- chronic diarrhea in immunocompromised
What is the pathogenic mech of EAEC?
- induction of mucus secretion which traps bacteria
- Bundle forming pili
- Presence of cytotoxin not proven
What are the characteristics of EIEC?
- most common in developing world
- attacks large bowel
- causes watery diarrhea that progresses to bloody diarrhea
- invades intestinal cell, multiplies within the cell, spreads to adjacent cells
- cause disease similar to shigella
- some suggest that shigella and EIEC are the same organism, just different LPS
- EIEC use same invasion genes as shigella
What are the characteristics of shigella?
- reservoir is human GI
- causes >200 million cases/year in diarrhea worldwide
- highly contagious
- serogroup based on O-antigen
- low inoculum causes disease
- person to person or through food
- HUS is a complication
- occurs in children more
What are the four serogroups of shigella ?
GroupA Shigella dysenteriae
GroupB Shigella flexneri GroupC Shigella boydii GroupD Shigella sonnei
Which strains of Shigella causes the more severe diseases?
S. dysenteriae and S. Flexneri
What is the pathogenesis of Shigella?
- acid tolerant
- invades cell of the large bowel leading to ulceration and abscesses
- type III secretion
- progresses in cells, spreads cell to cell
- all strains produce toxins
what is the mech of shiga toxin?
- A-B toxin
- binds Gb3 glycolipid
- internalized and stransported to the golgi
- A subunit is released to the cytoplasm
- A blocks tRNA binding
- blocks protein synthesis
Are there any effective vaccines for shigella and E. Coli?
no
