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MS 2 - Unit 6 > Microbiology - Shigella, E. coli, Toxigenic Gastroenteritis, Salm - Rebecca Greenblatt > Flashcards

Microbiology - Shigella, E. coli, Toxigenic Gastroenteritis, Salm - Rebecca Greenblatt Flashcards

1
Q

What medium is important for growing Shigella?

A

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)
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2
Q

What is the route of transmission of Shigella?

A

Fecal-oral;

human-restricted

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3
Q

Is Shigella anaerobic?

A

Facultative anaerobe;

Facultative intracellular

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4
Q

Shigella encodes what for invading host cells?

A

Type III Secretion System

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5
Q

What is the IU for Shigella?

A

Very low - like 100 IUs –. means they are good at surviving passage through the stomach

Shigella enterocolitis = bacillary dysentery = shigellosis all the same thing

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6
Q

What are the symptoms of shilgellosis?

A

Bloody diarrhea
Local inflammation
Small ulcerations of the ileum

People low on vitamin A and zinc have a worse prognosis

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7
Q

People who contract shigellosis are at risk for what complication?

A

Reactive arthritis - conjunctivitis, urethritis, arthritis

Tx with NSAIDS, can persist for 2 years (more commonly 6 months)

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8
Q

What is the pathogenesis for Shigella?

A

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

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9
Q

What is the primary virulence factor for Shigella?

A

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

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10
Q

Neutrophils are seen in methylene blue stains of fecal samples with what infections?

A

Shigella
Salmonella
Campylobacter

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11
Q

Neutrophils are NOT seen in methylene blue stains of fecal samples with what infections?

A

Vibrio cholerae
E. Coli
C. perfringens

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12
Q

HUS shows what in blood samples?

A

Schistocytes
Decreased platelets
Increased PMNs
Increased lactate dehydrogenase

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13
Q

In _______, antibiotic treatment decreases HUS risk.

A

Shigella

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14
Q

In _______, antibiotic treatment increases HUS risk.

A

E. Coli (EHEC = enterohemorrhagic E. Coli)

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15
Q

If malnourishment is suspected, what supplements should be included in the tx of Shigella?

A

Vitamin A and zinc

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16
Q

Fluoroquinolones should NOT be used in what population?

A

Children

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17
Q

What antibiotics are indicated in the treatment of Shigella?

A 
test for Ab sensitivity; 
ceftriaxone, 
fluoroquinolone, 
azithromycin,
cefixime 
usually work in adults
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18
Q

What is the phylogenetic grouping of E. Coli?

A

Gram negative rod
Enterobacteriacae
Ferments lactose

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19
Q 
E. Coli is:
H2S \_\_\_\_
Urease \_\_\_\_
Lactose \_\_\_\_\_
\_\_\_\_\_ anaerobe
A 
H2S negative
Urease negative
Lactose fermenter 
Facultative anaerobe
Can be mobile or not
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20
Q

Give the virulence factor for uropathogenic E. Coli.

A

Fimbrae

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21
Q

Give the virulence factor for enterotoxigenic E. Coli (ETEC).

A

Enterotoxin - pili - watery diarrhea

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22
Q

Give the virulence factor for enterohaemorrhagic E. Coli (EHEC).

A

Shiga-like toxin - bundle forming - bloody diarrhea with risk of HUS if reaches bloodstream

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23
Q

What is HUS?

A

acute renal failure, microangiopathic hemolytic anemia,
thrombocytopenia;
CNS symptoms possible;
10% DIC and lethality

PMNs↑, TNFα↑,
IL1↑, IL6↑,
von Willebrand factor↑

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24
Q

What is the MAIN issue causing the severity of HUS?

A

Capillary Occlusion: fibrin –platelet thrombi in renal microvasculature

Also GB3 receptor on CNS, kidney, RBC surfaces

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25
Q

Lactate dehydrogenase is a marker for:

A

kidney failure

26
Q

For E. Coli infection, culture stool sample on:

A

Blood agar and differential medium ie MacConkey’s

27
Q

What is the phylogenetic grouping of Salmonella?

A

Gram (-) rod
Enterobacteriacae
Non-lactose fermenting
H2S POSITIVE (producing)

28
Q

What medium is best to grow Salmonella on?

A

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

29
Q

Salmonella is responsible for what complications?

A

Enterocolitis
Enteric Fevers (typhoid fever)
Septicemia
Risk of reactive arthritis (Reiter’s Syndrome)

30
Q

What virulence factor is Salmonella known for?

A

Pili

Salmonellae selectively attach to specialized epithelial cells (M cells) of the Peyer patches.
The bacteria are then internalized by receptor-mediated endocytosis

31
Q

What medications increase the risk of contracting salmonella infection?

A

Antacids - bc gastric acid is protective

32
Q

What virulence factor is common to all the enterobacteriacae?

A

T3SS to subvert the M cell (immune evasion/host cell evasion)

33
Q

Salmonella needs a large or small IU to infect?

34
Q

What types of salmonella cause typhoid fever?

A

S. typhi

S paratyphi

35
Q

What is the mode of transmission of S. typhi

S paratyphi?

A

Human-restricted;

fecal-oral

36
Q

What virulence factor protects S. typhi, S paratyphi from humoral immunity?

A

Vi capsule

37
Q

Typhoid can be asymptomatically carried in what reservoir?

A

Gall bladder

38
Q

What do TB, Cryptococcus and Histoplasma and Typhoid (Salmonella) all have in common?

A

They all survive endocytosis and subsequently use the macrophage for systemic transport (Trojan Horse)

39
Q

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

40
Q

What physical finding is present in 25% of typhoid fever cases?

A

Rose spots (blanchable)

41
Q

A patient with SCD and salmonella infection can develop what complication?

A

Salmonella osteomyelitis (septicemia)

42
Q

What is the best way to culture typhoid?

A

Bone marrow aspirate

43
Q

For the enteric fever/septicemia associated with salmonella, what antibiotics are recommended?

A

Ceftriaxone

Ciprofloxacin

44
Q

What is the phylogency of Yersinia entercolitica and pseudotuberculosis?

A

Gram negative rod
Does not ferment lactose
Urease positive

**motile in cold, but not warm

45
Q

What is unique about Yersinia enterobacteriacae pathogenesis?

A

May spread locally to local lymph nodes –> mesenteric lymphadenitis (false appendicitis)

46
Q

Yersinia entercolitica and pseudotuberculosis both ?predispose what complication?

A

Reactive arthritis

47
Q

Yersinia entercolitica virulence is enhanced in the presence of iron overload because:

A

It does not produce its own siderophores

48
Q

Yersinia pseudotuberculosis can cause what disease in children?

A

Izumi fever

49
Q

What kind of agar should you grow Yersinia entercolitica and pseudotuberculosis

A

Cefsulodin-irgasan-novobiocin (CIN) agar

50
Q

What is the phylogeny of Listeria?

A

Gram positive
Non-spore forming
Facultative anaerobic
Beta-hemolytic

51
Q

How does listeria look on agar?

A

Blue-green sheen on non-blood agar;

grows well in cold

52
Q

What kind of motility does listeria have?

A

Tumbling motility - temperature-sensitive flagella

53
Q

Pregnant patients should avoic what foods to avoid infection with listeria?

A

Soft cheeses

Lunchmeats

54
Q

What virulence factors does listeria have?

A

Listerolysin;

ActA (actin rockets - way to avoid humoral immunity)

55
Q

Immunosuppressed patients who contract listeria can develop what complications?

A

Pregnancy complications;
Meningitis

Less commonly endocarditis, septic arthritis, osteomyelitis, rarely pneumonia

56
Q

Listeria uses what organ in pregnancy from which to seed?

A

Placenta

Commonly causes preterm labor, may cause abortion, stillbirth, intrauterine infection

57
Q

How should you culture listeria?

A

CSF wet mount - look for motile bacteria

58
Q

Listeria is resistant to what antibiotics?

A

All cephalosporins

59
Q

M cells are found in the:

A

Peyer’s patches

60
Q

Antibiotic choices for treating listeria are:

A

ampicillin+gentamicin or trimethoprim+sulfamethoxazole

MS 2 - Unit 6 (34 decks)

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