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Bacteriology > GI Bacteria > Flashcards

GI Bacteria Flashcards

1
Q

What is common about the structure of all the GI infecting bacteria?

A

They are all gram negative. Except Listeria and C.Diff

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2
Q

What bacteria can still grow at refrigerator temperatures?

A

Listeria. Humans are infected with L. Monocytogenes

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3
Q

What is the specific patient population of Listeria that cause the most problems?

A

Immunocompromised individuals. Neonates, Elderly, Pregnant women, and suppressed/defective immune system.

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4
Q

What is unique about life cycle of Listeria?

A

Can survive stomach acid, enters M-cell phagosome to escape into cytoplasm and replicate. ActA for actin mobility into other cells. Gram Positive

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5
Q

Where does Listeria come from?

A

undercooked meat, unpasterized milk, cheese, and unwashed vegetables.

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6
Q

Can Listeria be passed onto an unborn child, if so what happens?

A

Yes, the mother can pass on Listeria to the fetus and can cause abortion/still born, if late onset in child then meningitis/sepsis.

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7
Q

What are the disease symptoms of Listeria in immunocompromised adult and regular competent adult?

A

Competent adult - self limited mild GI illness few days

Immunocompromised individual - high mortality and meningitis

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8
Q

What class is Salmonella associated with?

A

Enterobacteriaceae Family

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9
Q

How does Salmonella invade a host?

A

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.

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10
Q

How are Typhoid/Enteric fever different from Salmonella invasion?

A

Typhoid/Enteric can invade macrophages and then spread systemically causing bacteremia.

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11
Q

How is the infectious dose different from Salmonella and Typhoid/Enteric fever?

A

Salmonella you need a high dose and Typhoid/Enteric Fever you need a very low dose, so it is very contagious.

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12
Q

What are the clinical differences between Salmonella and Enteric Fever?

A

Salmonella - 6-48 hour onset, self-limited GI symptoms

Enteric Fever - 10-14 days after infection - GI phase comes after the systemic symptoms

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13
Q

If someone gets bacteremia from Salmonella what should be concerning?

A

That they are immunocompromised.

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14
Q

What are characteristics of Shigella?

A

Gram Negative, Enterobacteriaceae, does not ferment lactose, no flagella, and low inoculation dose. Human only pathogen.

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15
Q

Where does Shigella replicate and how?

A

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.

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16
Q

What are symptoms caused by Shigella and why?

A

Produces Shiga Toxin that deadenylates 28S rRNA in binding site preventing protein synthesis and cell death.
Dysentery - bloody mucous diarrhea

17
Q

How can you tell between Shigella and Salmonella?

A

Salmonella is motile, produces H2S, and lactose negative.

Shigella - no flagella, does NOT produce H2S, and is also lactose negative.

18
Q

Treatment of Shigella?

A

Self-Limited and shouldn’t give Abx, unless severe. Vaccination can be used if traveling to south america, africa, or southern asia.

19
Q

Characteristics of E.Coli?

A

Gram Negative, Low inoculation dose, and family of Enterbacteria.

20
Q

What is the difference between EHEC and EPEC?

A

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

21
Q

What are symptoms caused by EHEC?

A

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.

22
Q

How do you identify EHEC from regular E.Coli?

A

Culture - EHAC unable to ferment sorbitol, but regular E.Coli can. EHAC = colorless E.Coli = pink
Can also detect the Shiga toxin by assay.

23
Q

Treatment of EHEC?

A

Prevention and supportive care. Abx can cause increased toxin release.

24
Q

What are the physical characteristics of Campylobacter?

A

Gram Negative, curved rod, spiral/comma shape, Grows at warmer temp 42C/slow growth, motile with flagella.

25
Q

Source of Campylobacter?

A

Primarily undercooked chicken, higher rate in the summer months.

26
Q

What are unique symptoms of Campylobacter?

A

Acute enteritis, bloody stools, ulcerative mucosa, and inflammation of bowels.

27
Q

What bacterium can cause autoimmune diseases like Guillian-Barre and Reactive Arthritis?

A

Campylobacter, due to being similar antigen configuration to the tissues involved, typically weeks after infection.

28
Q

How can you identify Campylobacter?

A

Fresh fecal samples with darting motile bacterium with RBCs and WBCs present.

29
Q

Physical characteristics of Helicobacter Pylori?

A

Gram Negative, curved rods, multiple flagella motile

30
Q

What allows H. Pylori to survive in the acid environment of the stomach?

A

Urease expression that converts NH3 to CO2 and remains close to the epithelium where pH is more neutral.

31
Q

What virulence factor genes of H. Pylori cause gastric/peptic ulcers?

A

VacA - forms anion channels altering tight junctions from large vacuoles.
Type IV Secretion System injecting CagA to induce the cell to produce IL-8 eliciting inflammatory response damaging tissue disrupting epithelium.

32
Q

What can H. Pylori cause long term?

A

Increases chances of cancer due to chronic inflammation. Gastric Adenocarcinoma and Gastric B-Cell Lymphoma

33
Q

How do you test for H.Pylori infection?

A

Urea breath test. Ingest radioactive urea and then test breath for radioactive CO2.

34
Q

What are characteristics of Vibrio?

A

Gram Negative, requries NaCl for growth, Oxidase Positive. Curved rods, single flagella.

35
Q

How does the Cholera toxin work?

A

A:5B toxin, binds GM1 receptor, A-subunit activates Gs stimulating secretion of Cl- and water. No destruction of cells.

36
Q

What else is encoded on the bacteriophage of Vibrio?

A

Cholera Toxin
Toxin Coregulated pilus - adherence
Zot - disrupts tight junctions
Ace - increases fluid secretion

37
Q

Where is Vibrio have highest incidence?

A

South America, Africa, and Asia

38
Q

What are common symptoms and treatment for Vibrio?

A

2-3 days after infection significant watery diarrhea with high mortality. Treatment is just to replace fluids.

39
Q

How is Vibrio contracted and prevented?

A

Contaminated water/food in underdeveloped countries and vaccine can be used to prevent binding of the toxins and colonization.

Bacteriology (14 decks)

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