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) *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 (6days) = meningitis
How is listeria treated?
-sensitive to most Abx, not B-lactams -must be a drug that can penetrate eukaryotic cells
