GI Bacteria Flashcards
(39 cards)
What is common about the structure of all the GI infecting bacteria?
They are all gram negative. Except Listeria and C.Diff
What bacteria can still grow at refrigerator temperatures?
Listeria. Humans are infected with L. Monocytogenes
What is the specific patient population of Listeria that cause the most problems?
Immunocompromised individuals. Neonates, Elderly, Pregnant women, and suppressed/defective immune system.
What is unique about life cycle of Listeria?
Can survive stomach acid, enters M-cell phagosome to escape into cytoplasm and replicate. ActA for actin mobility into other cells. Gram Positive
Where does Listeria come from?
undercooked meat, unpasterized milk, cheese, and unwashed vegetables.
Can Listeria be passed onto an unborn child, if so what happens?
Yes, the mother can pass on Listeria to the fetus and can cause abortion/still born, if late onset in child then meningitis/sepsis.
What are the disease symptoms of Listeria in immunocompromised adult and regular competent adult?
Competent adult - self limited mild GI illness few days
Immunocompromised individual - high mortality and meningitis
What class is Salmonella associated with?
Enterobacteriaceae Family
How does Salmonella invade a host?
Invades M-cells, replicates inside the “spacious” vacuole, modifying it and preventing immune response. Has pathogenicity island genes that encode virulence factors allowing invasion of host.
How are Typhoid/Enteric fever different from Salmonella invasion?
Typhoid/Enteric can invade macrophages and then spread systemically causing bacteremia.
How is the infectious dose different from Salmonella and Typhoid/Enteric fever?
Salmonella you need a high dose and Typhoid/Enteric Fever you need a very low dose, so it is very contagious.
What are the clinical differences between Salmonella and Enteric Fever?
Salmonella - 6-48 hour onset, self-limited GI symptoms
Enteric Fever - 10-14 days after infection - GI phase comes after the systemic symptoms
If someone gets bacteremia from Salmonella what should be concerning?
That they are immunocompromised.
What are characteristics of Shigella?
Gram Negative, Enterobacteriaceae, does not ferment lactose, no flagella, and low inoculation dose. Human only pathogen.
Where does Shigella replicate and how?
Localizes in the colon, invades M-cells - Ipa proteins induce uptake of bacterium Type III secretion, lysis the vacuole, replication in cytoplasm and apoptosis of phagocyte causing strong inflammation.
What are symptoms caused by Shigella and why?
Produces Shiga Toxin that deadenylates 28S rRNA in binding site preventing protein synthesis and cell death.
Dysentery - bloody mucous diarrhea
How can you tell between Shigella and Salmonella?
Salmonella is motile, produces H2S, and lactose negative.
Shigella - no flagella, does NOT produce H2S, and is also lactose negative.
Treatment of Shigella?
Self-Limited and shouldn’t give Abx, unless severe. Vaccination can be used if traveling to south america, africa, or southern asia.
Characteristics of E.Coli?
Gram Negative, Low inoculation dose, and family of Enterbacteria.
What is the difference between EHEC and EPEC?
EHEC/EPEC - both cause attaching/effacing lesions via Type III secretion to allow bacterium binding to epithelium in GI.
EHEC ONLY - Stx1/Stx2 toxins as well
What are symptoms caused by EHEC?
Range from mild to severe symptoms.
Hemorrhagic Colitis after 3-4 days of inoculation.
Hemolytic Uremic Sydrome in children - acute renal failure and hemolytic anemia.
How do you identify EHEC from regular E.Coli?
Culture - EHAC unable to ferment sorbitol, but regular E.Coli can. EHAC = colorless E.Coli = pink
Can also detect the Shiga toxin by assay.
Treatment of EHEC?
Prevention and supportive care. Abx can cause increased toxin release.
What are the physical characteristics of Campylobacter?
Gram Negative, curved rod, spiral/comma shape, Grows at warmer temp 42C/slow growth, motile with flagella.
