Microbiology - Shigella, E. coli, Toxigenic Gastroenteritis, Salm - Rebecca Greenblatt Flashcards
What medium is important for growing Shigella?
MacConkey’s selective differential medium
- -will not grow gram + things (ie listeria)
- -will turn pink in presence of organic acids (E. Coli ferments lactose –> medium turns pink, Proteus does not ferment lactose –> colony remains white)
What is the route of transmission of Shigella?
Fecal-oral;
human-restricted
Is Shigella anaerobic?
Facultative anaerobe;
Facultative intracellular
Shigella encodes what for invading host cells?
Type III Secretion System
What is the IU for Shigella?
Very low - like 100 IUs –. means they are good at surviving passage through the stomach
Shigella enterocolitis = bacillary dysentery = shigellosis all the same thing
What are the symptoms of shilgellosis?
Bloody diarrhea
Local inflammation
Small ulcerations of the ileum
People low on vitamin A and zinc have a worse prognosis
People who contract shigellosis are at risk for what complication?
Reactive arthritis - conjunctivitis, urethritis, arthritis
Tx with NSAIDS, can persist for 2 years (more commonly 6 months)
What is the pathogenesis for Shigella?
Shigella invade epithelium of distal ileum and colon epithelium (M cells –> macrophages –> T3SS) and secrete exotoxins
Exotoxin pathway kills adjacent cells
Cell necrosis, apoptosis, host inflammatory response and hemorrhage lead to the bloody diarrhea
What is the primary virulence factor for Shigella?
Shiga toxin
Also siderophores allow it to chelate iron, and pili allow for attachment
IcsA is involved in bacterial use of host actin to cross into neighboring cells directly
IpaB induces macrophage apoptosis ➔ no phagocytosis, increases inflammatory response
Neutrophils are seen in methylene blue stains of fecal samples with what infections?
Shigella
Salmonella
Campylobacter
Neutrophils are NOT seen in methylene blue stains of fecal samples with what infections?
Vibrio cholerae
E. Coli
C. perfringens
HUS shows what in blood samples?
Schistocytes
Decreased platelets
Increased PMNs
Increased lactate dehydrogenase
In _______, antibiotic treatment decreases HUS risk.
Shigella
In _______, antibiotic treatment increases HUS risk.
E. Coli (EHEC = enterohemorrhagic E. Coli)
If malnourishment is suspected, what supplements should be included in the tx of Shigella?
Vitamin A and zinc
Fluoroquinolones should NOT be used in what population?
Children
What antibiotics are indicated in the treatment of Shigella?
test for Ab sensitivity; ceftriaxone, fluoroquinolone, azithromycin, cefixime usually work in adults
What is the phylogenetic grouping of E. Coli?
Gram negative rod
Enterobacteriacae
Ferments lactose
E. Coli is: H2S \_\_\_\_ Urease \_\_\_\_ Lactose \_\_\_\_\_ \_\_\_\_\_ anaerobe
H2S negative Urease negative Lactose fermenter Facultative anaerobe Can be mobile or not
Give the virulence factor for uropathogenic E. Coli.
Fimbrae
Give the virulence factor for enterotoxigenic E. Coli (ETEC).
Enterotoxin - pili - watery diarrhea
Give the virulence factor for enterohaemorrhagic E. Coli (EHEC).
Shiga-like toxin - bundle forming - bloody diarrhea with risk of HUS if reaches bloodstream
What is HUS?
acute renal failure, microangiopathic hemolytic anemia,
thrombocytopenia;
CNS symptoms possible;
10% DIC and lethality
PMNs↑, TNFα↑,
IL1↑, IL6↑,
von Willebrand factor↑
What is the MAIN issue causing the severity of HUS?
Capillary Occlusion: fibrin –platelet thrombi in renal microvasculature
Also GB3 receptor on CNS, kidney, RBC surfaces