What organism are we thinking when we hear "leather throat" and "Bull neck?"
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?
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?
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?
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
What are the microbiologic features of Bacillus?
-Gm + -encapsulated, spore-forming (white) -grow in long end-to-end chains (looks like fungus) -non-motile
What culture medium does bacillus grow on?
-simple carbon and nitrogen sources -grows pretty much everywhere
How is B. antrhacis distinguished from B. cereus?
-anthracis requires thiamin to grow -cereus = hemolysis on blood agar
How is bacillus anthracis inoculated in humans?
-cutaneous (black eschar) -intestinal -Pulmonary
What are the x-ray findings of inhalational anthrax?
Why have anthrax infections decreased since the 60's?
How does B. anthracis cause disease?
-spores phagocytosed by macrophates and transported to lymphatics -releases 3 exotoxins: EF, LF, and PA -death is due to septicemia, toxemia, and shock
What are the virulence factors (& toxins) of B. anthracis?
-Antiphagocytic capsule (very protective) Tripartite toxin: -Lethal factor (LF) -Edema Factor (EF) -protective antigen (PA) binds to cell and activates toxin release
What is the treatment for anthrax?
-susceptible to penicillin (but usually too late) -anthrax vaccine
What disease does Bacillus cereus cause?
What are the virulence factors produced by Bacillus cereus?
-Emetic toxin = vomiting 6hrs after -Gastrointestinal toxin = diarrhea
What invasive diseases are caused by Bacillus cereus?
-soft tissue disease = cellulitis in leukemics/immunocompromised -eye infection -pulmonary infection
Fried rice and diarrhea! what organism we thinkin?
What are the two most common causes of meningitis in people over 50?
#1 Strep pneumoniae #2 Listeria
"large Gm+ rods in chains"
"re-heated fried rice"
What are the toxins produced by Bacillus cereus?
-Heat labile -heat stable
What organisms cause pediatric meningitis at less than 3 months of age and greater than 3 months?
3 mo: -Neisseria meningitides -H. influenzae
"Loeffler coagulated serum & Cystine-tellurite blood agar"
"pseudomembrane in oropharynx"
"tumbling club-shaped bacillus"
"soft cheese & cold cuts"