Diphtheria, Listeria, & Bacillus Flashcards
What organism are we thinking when we hear “leather throat” and “Bull neck?”
Diphtheria
What are the microbiological characteristics of Diphtheria?
- Club shaped
- Gram positive (sometimes gram variable in resp sample)
- Granules (polymetaphosphate) visible when stained with methylene
What media can we culture Diphtheria on?
- Loeffler coagulated serum
- Cystine-tellurite blood agar (black colonies)
How does Diphtheria spread?
- human -> human
- Droplets or direct contact with skin abrasions
Where does diphtheria colonize?
Mucous membranes
-mostly tonsils and pharynx
**no invasion
How does diphtheria cause disease?
-virulence factor = exotoxin
= diphtheria toxin
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
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
What is Bull Neck?
- caused by diphtheria
- lymphadenopathy and edema
Is diphtheria catalase positive or negative?
-Positive
How do we treat diphtherai?
*Tx must be prompt!
- Antitoxin (DAT)
- Antibiotics (penicillin & erythomycin)
- Tdap
*vaccination makes disease very rare
Where does Listeria like to live?
- food-borne pathogen
- cheeses, cold cuts and hot dogs
**think bluebell outbreak
What organisms do we worry about with soft unpasteurized cheeses?
- Listeria
- Brucella
Who is susceptible to infection by Listeria?
- Immunocompromised: elderly & AIDS, transplant patients
- pregnant women, can cross to fetus
What is the microbiology of Listeria?
- Gm + bacillus
- Resistant to high salt and bile concentrations
- covered in flagella
- can multiply at 4 degrees celcius
Is listeria catalase positive or negative?
Positive
Why is listeria scary in the fridge?
It can multiply at 4 degrees celcius
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
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
What does listeriolysin O of lysteria do?
-allows organism release from a phagosome
Why is there no vaccine for Listeria?
-antibody immunity will not save us
What diseases are caused by listeria?
- Maternal listeriosis (33%)
- perinatal listerosis
- focal infection (GI, Liver)
- sepsis & meningitis in immunocompromised
What is the difference between presentation of early onset and late onset perinatal listerosis?
Early (<6 days) = bacteremia
Late (>6 days) = meningitis
How is listeria treated?
- sensitive to most Abx, not B-lactams
- must be a drug that can penetrate eukaryotic cells
