Mycos (-plasma, -bacterium) Flashcards
What characterizes mycobacterium structurally?
Acid-fast –> due to high lipid laden walls. Cell walls don’t dissolve in acid, so red stain doesn’t wash off. “Fast red car” –> acid fast organisms stain red.
What is mycolic acid?
Large fatty acid bound to carbohydrate, forming a glycolipid. Found in mycobacterium tuberculosis.
What is cord factor?
In virulent strains of mycobacterium tuberculosis, inhibits macrophage maturation and induces release of TNF-alpha.
What are sulfatides?
In mycobacterium tuberculosis, inhibits phagolysosomal fusion, facilitates intracellular survival.
What population does mycobacterium avium intracellulare cause disease in?
AIDs patients with CD4 count < 50.
- Disseminated infection with fever, weight loss, hepatitis, and diarrhea.
What ppx is there for MAI?
Azithromycin with CD4 count >50.
What population does mycobacterium scrofulaceum cause disease in?
cervical lymphadenitis in children.
What population does mycobacterium marinum cause disease in?
Hand infection in aquarium handlers.
What is Hansen disease caused by?
Mycobacterium leprae.
In what temperature does M. leprae grow best in?
Cool temperatures - infects skin and superficial nerves - glove/stocking loss of sensation. Cannot be grown in vitro.
What is the reservoir of M. leprae in the US?
armadillos
What is the presentation of lepromatous form of M. leprae?
Presents diffusely over the skin, with lionlike facies - contagious.
What is the immune response to lepromatous form of M. leprae?
Low cell-mediated immunity, humoral th2 response.
What is the presentation of the tuberculoid form of M. leprae?
Few hypoesthetic, hairless skin plaques.
What is the immune response to the tuberculoid form of M. leprae?
High cell-mediated immunity with largely Th1 type immune response.
What is the treatment for tuberculoid form of M. leprae?
Dapsone, rifampin.
What is the treatment for lepromatous form of M. leprae?
Dapsone, rifampin, clofazimine.
What is special about the structure of mycoPLASMAS?
No cell wall - not seen on gram stain! Pleomorphic - round to oblong shaped. Very small (smaller than some viruses). Bacterial wall contains sterols for stability.
What do mycoplasmas need to grow?
Cholesterol required for membrane synthesis. Eaton Agar.
Why is penicillin ineffective against mycoplasmas?
No cell wall.
What kind of hemolysis does Mycoplasma cause?
Cold agglutins; IgM. Binds to “I” antigen of RBCs at cold temperatures. 1st or 2nd week of mycoplasma infection.
What does Mycoplasma pneumoniae classically cause?
“Walking” pneumonia: insidious onset, headache, non-productive cough, patchy/diffuse interstitial infiltration that looks worse on Xray than the patient looks.
In what patients is M. pneumoniae infection more common?
Patients <30 yrs old.
Military recruits, prisons.
What is the treatment for M. Pneumoniae?
macrolides, doxycycline, or fluoroquinolones.
What organism can cause non-gonococcal urethritis with yellow mucoid discharge from the urethra?
Ureaplasma urealyticum.
What does ureaplasma require for growth?
Cholesterol and urea. Urease metabolizes urea into ammonia and CO2.
