Mycobacteria, etc. (Acid fast)

Question 1

Mycobacterium tuberculosis

Answer 1

Acid fast. High lipid content- Mycolic acid (wax). Cord factor (inhibits migration of leukocytes). Intracellular parasite of macrophages.

“Fever, night sweats, weight loss, hemoptysis (throwing up blood). Ghon complex (initial infection in lungs is containted within Gohn complex, pulmonary granuloma). Latent TB. Host immune response – cavitary lesions. Reactivation pulmonary TB (lungs). Extrapulmonary TB (elsewhere). Pott’s disease in vertebrae.
Lab diagnosis: Ziehl-Neelson stains mycobacterium red with blue background. 2 types of IGRA: T-spot test, Quantiferon-TB gold.”

Question 2

Mycobacterium leprae

Answer 2

Grows at low body temp.

Multiple nodular skin lesions that can coalesce producing disfiguring results (leonine facies). Armadillos (natural reservoir). Poor cell-mediated immunity. Infects skin and peripheral nerves (temp. lower than body).

Question 3

Nocardia asteroides

Answer 3

Cat (+). Partially acid fast. Branching filaments (looks like fungus).

Pneumonia in immunosuppressed - esp. transplant patients. Directly into skin by walking barefoot.