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Term 4: Infectious Diseases > 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) *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 (6days) = 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 #2 Listeria

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 are the toxins produced by Bacillus cereus?

A

-Heat labile -heat stable

43
Q

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

A

3 mo: -Neisseria meningitides -H. influenzae

44
Q

“Loeffler coagulated serum & Cystine-tellurite blood agar”

A

-Diphtheria

45
Q

“Bull neck”

A

-Diphtheria

46
Q

“pseudomembrane in oropharynx”

A

-Diphtheria

47
Q

“tumbling club-shaped bacillus”

A

Listeria monocytogenes

48
Q

“soft cheese & cold cuts”

A

Listeria monocytogenes

49
Q

“black eschar”

A

-cutaneous anthrax

Term 4: Infectious Diseases (21 decks)

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