Flashcards in Microbiology - Shigella, E. coli, Toxigenic Gastroenteritis, Salm - Rebecca Greenblatt Deck (60):
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?
Is Shigella anaerobic?
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?
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?
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?
Neutrophils are NOT seen in methylene blue stains of fecal samples with what infections?
HUS shows what in blood samples?
Increased lactate dehydrogenase
In _______, antibiotic treatment decreases HUS risk.
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?
What antibiotics are indicated in the treatment of Shigella?
test for Ab sensitivity;
usually work in adults
What is the phylogenetic grouping of E. Coli?
Gram negative rod
E. Coli is:
Can be mobile or not
Give the virulence factor for uropathogenic E. Coli.
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,
CNS symptoms possible;
10% DIC and lethality
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
Lactate dehydrogenase is a marker for:
For E. Coli infection, culture stool sample on:
Blood agar and differential medium ie MacConkey's
What is the phylogenetic grouping of Salmonella?
Gram (-) rod
H2S POSITIVE (producing)
What medium is best to grow Salmonella on?
Salmonella-Shigella agar medium
H2S turns the agar black (how you know it's Salmonella);
Lactose fermenters like E. Coli turn pink on this medium, just like MacConkey's
Salmonella is responsible for what complications?
Enteric Fevers (typhoid fever)
Risk of reactive arthritis (Reiter’s Syndrome)
What virulence factor is Salmonella known for?
Salmonellae selectively attach to specialized epithelial cells (M cells) of the Peyer patches.
The bacteria are then internalized by receptor-mediated endocytosis
What medications increase the risk of contracting salmonella infection?
Antacids - bc gastric acid is protective
What virulence factor is common to all the enterobacteriacae?
T3SS to subvert the M cell (immune evasion/host cell evasion)
Salmonella needs a large or small IU to infect?
What types of salmonella cause typhoid fever?
What is the mode of transmission of S. typhi
What virulence factor protects S. typhi, S paratyphi from humoral immunity?
Typhoid can be asymptomatically carried in what reservoir?
What do TB, Cryptococcus and Histoplasma and Typhoid (Salmonella) all have in common?
They all survive endocytosis and subsequently use the macrophage for systemic transport (Trojan Horse)
Penetration of gut is resisted by the ________ allele; protective effect against typhoid fever, cholera, and tuberculosis may explain persistence of allele despite lethality to homozygotes
What physical finding is present in 25% of typhoid fever cases?
Rose spots (blanchable)
A patient with SCD and salmonella infection can develop what complication?
Salmonella osteomyelitis (septicemia)
What is the best way to culture typhoid?
Bone marrow aspirate
For the enteric fever/septicemia associated with salmonella, what antibiotics are recommended?
What is the phylogency of Yersinia entercolitica and pseudotuberculosis?
Gram negative rod
Does not ferment lactose
**motile in cold, but not warm
What is unique about Yersinia enterobacteriacae pathogenesis?
May spread locally to local lymph nodes --> mesenteric lymphadenitis (false appendicitis)
Yersinia entercolitica and pseudotuberculosis both ?predispose what complication?
Yersinia entercolitica virulence is enhanced in the presence of iron overload because:
It does not produce its own siderophores
Yersinia pseudotuberculosis can cause what disease in children?
What kind of agar should you grow Yersinia entercolitica and pseudotuberculosis
Cefsulodin-irgasan-novobiocin (CIN) agar
What is the phylogeny of Listeria?
How does listeria look on agar?
Blue-green sheen on non-blood agar;
grows well in cold
What kind of motility does listeria have?
Tumbling motility - temperature-sensitive flagella
Pregnant patients should avoic what foods to avoid infection with listeria?
What virulence factors does listeria have?
ActA (actin rockets - way to avoid humoral immunity)
Immunosuppressed patients who contract listeria can develop what complications?
Less commonly endocarditis, septic arthritis, osteomyelitis, rarely pneumonia
Listeria uses what organ in pregnancy from which to seed?
Commonly causes preterm labor, may cause abortion, stillbirth, intrauterine infection
How should you culture listeria?
CSF wet mount - look for motile bacteria
Listeria is resistant to what antibiotics?
M cells are found in the: