19. TUBERCULOSIS

Question 1

Mycobaterium tuberculosis:

Answer 1

an immobile, gram-positive aerobe and facultative anaerobe.

Question 2

Pathogenesis of tuberculosis:

Answer 2

Immunity in tuberculosis is cell-mediated.
M. tuberculosis binds to alveolar macrophages.
Th1 cells proliferate, express specific receptors for the mycobacterial antigen and convert to immunocytes or memory T cells; the time from sensitization to immunocyte-conversion is 6-8 weeks and is called allergy virage.
Allergic reaction involves the same cells that mediate the immunity in tuberculosis - sensitized Th1 lymphocytes, activated macrophages, cytotoxic cells with cytokine release.
Primary bacteremia and specific granuloma develop along with the associated immune phenomena.
Caseous necrosis is the hallmark of tuberculous granuloma.

Question 3

Symptoms in patients with active disease:

Answer 3

Patients with active disease characteristically present with fever, weight loss, night sweats, and a productive cough (with or without hemoptysis) that does not respond to conventional antibiotic therapy.

Question 4

Mycobacterium species cauing TB:

Answer 4

M. tuberculosis (95%)
M. bovis
M. africanum

Question 5

TB treatment regiment:

Answer 5

• Intensive phase - rifampin, isoniazid, pyrazinamine, ethambutol for 4 months
• Continuation phase - rifampin + isoniazid for 4 months

Question 6

Staining of M. tuberculosis:

Answer 6

Ziehl-neelsen stain - acid-fast bacilli appear pink

Question 7

Tuberculin skin test:

Answer 7

• Measure after 72 hours
• 0-5mm -> negative reaction
• 6-14mm -> normergenic reaction
• > 15mm -> hyperergic reaction

** interferon gamma resistance assay test