Diphtheria, Listeria, & Bacillus Flashcards Preview

Term 4: Infectious Diseases > Diphtheria, Listeria, & Bacillus > Flashcards

Flashcards in Diphtheria, Listeria, & Bacillus Deck (49)
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1

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

Diphtheria

2

What are the microbiological characteristics of Diphtheria?

-Club shaped -Gram positive (sometimes gram variable in resp sample) -Granules (polymetaphosphate) visible when stained with methylene

3

What media can we culture Diphtheria on?

-Loeffler coagulated serum -Cystine-tellurite blood agar (black colonies)

4

How does Diphtheria spread?

-human -> human -Droplets or direct contact with skin abrasions

5

Where does diphtheria colonize?

Mucous membranes -mostly tonsils and pharynx **no invasion

6

How does diphtheria cause disease?

-virulence factor = exotoxin = diphtheria toxin

7

How does diphtheria toxin work?

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

8

What are the symptoms of Diphtheria?

-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

9

What is Bull Neck?

-caused by diphtheria -lymphadenopathy and edema

10

Is diphtheria catalase positive or negative?

-Positive

11

How do we treat diphtherai?

*Tx must be prompt! -Antitoxin (DAT) -Antibiotics (penicillin & erythomycin) *vaccination makes disease very rare

12

Where does Listeria like to live?

-food-borne pathogen -cheeses, cold cuts and hot dogs **think bluebell outbreak

13

What organisms do we worry about with soft unpasteurized cheeses?

-Listeria -Brucella

14

Who is susceptible to infection by Listeria?

-Immunocompromised: elderly & AIDS, transplant patients -pregnant women, can cross to fetus

15

What is the microbiology of Listeria?

-Gm + bacillus -Resistant to high salt and bile concentrations -covered in flagella -can multiply at 4 degrees celcius

16

Is listeria catalase positive or negative?

Positive

17

Why is listeria scary in the fridge?

It can multiply at 4 degrees celcius

18

How does listeria invade?

-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

19

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

-T-cells, because it is a facultative intracellular pathogen **cell mediated immunity important! not there in neonates and immunocompromised/HIV

20

What does listeriolysin O of lysteria do?

-allows organism release from a phagosome

21

Why is there no vaccine for Listeria?

-antibody immunity will not save us

22

What diseases are caused by listeria?

-Maternal listeriosis (33%) -perinatal listerosis -focal infection (GI, Liver) -sepsis & meningitis in immunocompromised

23

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

-Early (6days) = meningitis

24

How is listeria treated?

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

25

What are the microbiologic features of Bacillus?

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

26

What culture medium does bacillus grow on?

-simple carbon and nitrogen sources -grows pretty much everywhere

27

How is B. antrhacis distinguished from B. cereus?

-anthracis requires thiamin to grow -cereus = hemolysis on blood agar

28

How is bacillus anthracis inoculated in humans?

-cutaneous (black eschar) -intestinal -Pulmonary

29

What are the x-ray findings of inhalational anthrax?

-mediastinal widening

30

Why have anthrax infections decreased since the 60's?

Animal vaccination