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Term 4: ID practice > Diphtheria, Listeria, & Bacillus > Flashcards

Diphtheria, Listeria, & Bacillus Flashcards

1
Q

What organism are we thinking when we hear “leather throat” and “Bull neck?”

A

Diphtheria

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2
Q

What are the microbiological characteristics of Diphtheria?

A
  • Club shaped
  • Gram positive (sometimes gram variable in resp sample)
  • Granules (polymetaphosphate) visible when stained with methylene
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3
Q

What media can we culture Diphtheria on?

A
  • Loeffler coagulated serum
  • Cystine-tellurite blood agar (black colonies)
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4
Q

How does Diphtheria spread?

A
  • human -> human
  • Droplets or direct contact with skin abrasions
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5
Q

Where does diphtheria colonize?

A

Mucous membranes

-mostly tonsils and pharynx

**no invasion

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6
Q

How does diphtheria cause disease?

A

-virulence factor = exotoxin

= diphtheria toxin

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7
Q

How does diphtheria toxin work?

A
  • kills cells via inhibition of protein synthesis
  • enters cells via receptor-mediated endocytosis
  • Mucosal necrosis
  • toxin can travel in blood
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8
Q

What are the symptoms of Diphtheria?

A
  • Soar throat -fever (doesn’t exceed 102)
  • “pseudomembrane” of necrotic epithelium
  • death by suffocation or toxic myocarditis in heart (arrythmia & myocarditis)

*paralysis in 10-20% of pts, also neuropathy

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9
Q

What is Bull Neck?

A
  • caused by diphtheria
  • lymphadenopathy and edema
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10
Q

Is diphtheria catalase positive or negative?

A

-Positive

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11
Q

How do we treat diphtherai?

A

*Tx must be prompt!

  • Antitoxin (DAT)
  • Antibiotics (penicillin & erythomycin)
  • Tdap

*vaccination makes disease very rare

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12
Q

Where does Listeria like to live?

A
  • food-borne pathogen
  • cheeses, cold cuts and hot dogs

**think bluebell outbreak

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13
Q

What organisms do we worry about with soft unpasteurized cheeses?

A
  • Listeria
  • Brucella
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14
Q

Who is susceptible to infection by Listeria?

A
  • Immunocompromised: elderly & AIDS, transplant patients
  • pregnant women, can cross to fetus
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15
Q

What is the microbiology of Listeria?

A
  • Gm + bacillus
  • Resistant to high salt and bile concentrations
  • covered in flagella
  • can multiply at 4 degrees celcius
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16
Q

Is listeria catalase positive or negative?

A

Positive

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17
Q

Why is listeria scary in the fridge?

A

It can multiply at 4 degrees celcius

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18
Q

How does listeria invade?

A
  • enters M-cells and gets to bloodstream
  • Uses surface protein invasin/internalin to bind to macrophage and invade
  • listeriolysin O releases the bacterium from the phagosome
  • actin filaments allow bacteria to cross from one cell to another
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19
Q

What cells do you need to get rid of a listeria infection?

A

-T-cells, because it is a facultative intracellular pathogen

**cell mediated immunity important! not there in neonates and immunocompromised/HIV

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20
Q

What does listeriolysin O of lysteria do?

A

-allows organism release from a phagosome

21
Q

Why is there no vaccine for Listeria?

A

-antibody immunity will not save us

22
Q

What diseases are caused by listeria?

A
  • Maternal listeriosis (33%)
  • perinatal listerosis
  • focal infection (GI, Liver)
  • sepsis & meningitis in immunocompromised
23
Q

What is the difference between presentation of early onset and late onset perinatal listerosis?

A

Early (<6 days) = bacteremia

Late (>6 days) = meningitis

24
Q

How is listeria treated?

A
  • sensitive to most Abx, not B-lactams
  • must be a drug that can penetrate eukaryotic cells
25
Q

What are the microbiologic features of Bacillus?

A
  • Gm +
  • encapsulated, spore-forming (white)
  • grow in long end-to-end chains (looks like fungus)
  • non-motile
26
Q

What culture medium does bacillus grow on?

A
  • simple carbon and nitrogen sources
  • grows pretty much everywhere
27
Q

How is B. antrhacis distinguished from B. cereus?

A
  • anthracis requires thiamin to grow
  • cereus = hemolysis on blood agar
28
Q

How is bacillus anthracis inoculated in humans?

A
  • cutaneous (black eschar)
  • intestinal
  • Pulmonary
29
Q

What are the x-ray findings of inhalational anthrax?

A

-mediastinal widening

30
Q

Why have anthrax infections decreased since the 60’s?

A

Animal vaccination

31
Q

How does B. anthracis cause disease?

A
  • spores phagocytosed by macrophates and transported to lymphatics
  • releases 3 exotoxins: EF, LF, and PA
  • death is due to septicemia, toxemia, and shock
32
Q

What are the virulence factors (& toxins) of B. anthracis?

A

-Antiphagocytic capsule (very protective)

Tripartite toxin:

  • Lethal factor (LF)
  • Edema Factor (EF)
  • protective antigen (PA) binds to cell and activates toxin release
33
Q

What is the treatment for anthrax?

A
  • susceptible to penicillin (but usually too late)
  • anthrax vaccine
34
Q

What disease does Bacillus cereus cause?

A

-food poisoning

35
Q

What are the virulence factors produced by Bacillus cereus?

A
  • Emetic toxin = vomiting 6hrs after
  • Gastrointestinal toxin = diarrhea
36
Q

What invasive diseases are caused by Bacillus cereus?

A
  • soft tissue disease = cellulitis in leukemics/immunocompromised
  • eye infection
  • pulmonary infection
37
Q

Fried rice and diarrhea! what organism we thinkin?

A

Bacillus cereus

38
Q

What are the two most common causes of meningitis in people over 50?

A

1 Strep pneumoniae

39
Q

“mediastinal widening”

A

Bacillus anthracis

40
Q

“large Gm+ rods in chains”

A

Bacillus anthracis

41
Q

“re-heated fried rice”

A

Bacillus cereus

42
Q

What organisms cause pediatric meningitis at less than 3 months of age and greater than 3 months?

A

**< 3 mo: **

  • Group B strep
  • E. coli
  • Listeria monocytogenes

>3 mo:

  • Neisseria meningitides
  • H. influenzae
43
Q

“Loeffler coagulated serum & Cystine-tellurite blood agar”

A

-Diphtheria

44
Q

“Bull neck”

A

-Diphtheria

45
Q

“pseudomembrane in oropharynx”

A

-Diphtheria

46
Q

“tumbling club-shaped bacillus”

A

Listeria monocytogenes

47
Q

“soft cheese & cold cuts”

A

Listeria monocytogenes

48
Q

“black eschar”

A

-cutaneous anthrax

Term 4: ID practice (22 decks)

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