Enteric Bac 1 Flashcards
What is the gram stain of Shigella?
Gram neg rod
Does shigella need a high dose or low dose to infect?
Low dose
What complications are pts at risk of developing with shigella infection?
Reactive arthritis–reiter’s syndrome
Hemolytic-Uremic Syndrome–HUS
Pts who develop reactive arthritis as a complication of shigella infection are positive for?
HLA-B27
What does the plasmid of Shigella carry in order to parasitize enough iron to grow to large numbers?
Genes for siderophores–iron-chelating molecules
Where does the shigella enter the ileum and colon?
M cells of Peyer’s patch
Uses a type III secretion system
What is the type 3 secretion system virulence factor of shigella involved in?
Injects M cell–enhances bacterial translocation and decreases inflammatory response
What is the IcsA virulence factor of shigella involved in?
Bacterial use of host actin to cross into neighboring cells directly
What is the IpaB virulence factor of shigella involved in?
Induces macrophage apoptosis–> no phagocytosis, increases inflammatory response
When does HUS begin?
When shiga toxin escapes into blood stream
What is seen on PE of pt with shigella infection?
Fever
Dehydration
Severe HA
Progression from watery to bloody diarrhea
What is seen on the bloodwork of a pt with HUS from shigella?
Schistocytes
Decreased platelets
Increased PMNs
Increased lactate dehydrogenase
If neutrophils are present on methylene blue stain of fecal sample then whats the ddx?
Shigella
Salmonella
Campylobacter
If neutrophils are NOT present on methylene blue stain of fecal sample then whats the ddx?
V. cholerae
E. coli
C. perfringens
Does Abx treatment in shigella increase or decrease HUS risk?
Decreases HUS risk–opposite of EHEC
What is the gram stain for E. coli?
Gram negative rod
What virulence factor is present in E. coli that allows for adherence to host cell?
Fimbriae
What virulence factor is present with E. coli allowing molecules to force cell to form actin bundle, causing inflammation?
Type 3 and/or 4 secretion systems
What virulence factor is present with E. coli that allows actin-based cell-to-cell motility just like in shigella?
IcsA
What is the pathogenesis of gastroenteritis caused by E. coli?
Watery diarrhea–bacteria use timbre to attach to gut lining–attach to jejunum and ileum
LT–Enterotoxins force host cells to release fluids, potassium and Chloride
What is the pathogenesis of bloody gastroenteritis caused by e. coli?
EHEC attach to the mucosal epithelial cells of the colon
Lysogenic phage STX encodes Shiga toxin–Becomes active in the gut cells, shuts down protein synthesis and destroys some
Causes inflammation and bloody diarrhea
Toxin may reach blood stream causing HUS
What is seen with HUS caused by E. coli?
Fever Dehydration Thrombocytopenia Uremia requiring dialysis Blood smear--Schistocytes, low platelets, High PMNs, elevated serum level of lactate dehydrogenase
If Abx are used for tx of enterohemorrhagic diarrhea caused by E. coli what is the pt at risk of developing?
HUS–opposite of shigella
What is seen with staph aureus, bacillus cereus food poisoning and food borne botulism?
Rapid onset—HOURS, not days
