Tuberculosis Flashcards
Causative agent
Mycobacterium tuberculosis
Infection begins when…
bacteria reach lung alveoli
Histopathological changes
- granulomatous inflammation can form caseating and non-caseating tubercles
- tuberculous granuloma –> central caseous necrosis, transformed macrophages, lymphocytes, plasma cells, fibroblasts
Clinical features
pulmonary TB
extrapulmonary Tb –> pleuritis, peripheral lymphadenopathy, tubercular meningitis, skeletal TB, GI TB, renal, skin
Active TB disease
-symptoms
-there may be none
- systemic: fever, night sweats, weight loss, fatigue, chills, feeling weak/tired, loss of appetite
- pulmonary: coughing (>3w.), chest pain, hemoptysis
Active TB disease
- radiographic appearance (4)
- complications
- upper lobe consolidation
- cavitary lesions
- tuberculomas - single or multiple focal lesions, peripheral derivatives
- lymphadenopathy
- effusions
- miliary pattern (dissemination of bacilli, nodular opacities, scattered diffusely throughout both lungs )
Active TB disease
-differential of a miliary pattern (5)
- sarcoidosis
- metastatic neoplastic disease
- pneumoconiosis
- atypical mycobacteria
- fungal or viral infection
Active TB disease
-diagnosis
- 1st step - x-ray
- microscopy: Ziehl-Neelsen dyed (acid-fast bacteria) –> one smear is not enough, at least 2 are necessary. However, not all acid-fast bacteria are M.tuberculosis.
- culture: gold standard –> solid (egg or agar based) or liquid (Middle brook) medium
- CT - when it is necessary to differentiate between other diseases
- PCR - fast but too expensive
Which segments of the lung are more vulnerable because they are more ventilated?
S1, S2, S6
Active TB disease
-when to suspect?
- addiction
- lack of social skills
- long term stress
- malnutrition
- prolonged starvation
- homelessness
- having lived in Asia/ Latin America/ Easter Europe/ Africa
- sustained cough >3w.
When should an x-ray be performed?
- before a diagnosis is set
- after 2m. of intensive treatment
- every 2-4m. of continuation phase
- in the 5th month of treatment
- before and after treatment
Classification
A15 - resp. tuberculosis confirmed bacteriological and/or histo
A16 - resp. tuberculosis not confirmed bacteriological and/or histo
A17 - tuberculosis of the nervous system
A18 - tuberculosis of other organs (bones, joints, skin, eyes…)
A19 - miliary tuberculosis
TB case definitions (5)
New case - never treated or never taken anti-TB for less than 1m.
Relapse - previously treated –> declared cured or completed treatment –> diagnosed again
Treatment after failure - have been treated or treatment
failed at the end of their most recent course of treatment
Treatment after loss to follow up
Other previous treatment
Drug resistance classification (5)
- Primary drug resistance - due to infection with resistant bacilli
- Acquired drug resistance - among those previously treated or from exogenous reinfection with resistant bacilli
- Multi-drug resistance (MDR) - resistant to at least isoniazid and rifampicin
- Extensive drug resistance (XDR) - isoniazid and rifampicin, a fluoroquinolone, and one or more of the following injectable drugs: amikacin, capreomycin, or kanamycin
- Rifampicin resistance - with or without resistance to other TB drugs
Treatment
- phases and duration
- what happens in each phase
Phase 1 (1+2, lasts 2, sometimes 3 months) –> intensive phase
Phase 2 (3, lasts 4-7m.) –> continuation phase
- within 2w. –> intercellular M.tuberculosis is destroyed –> patient is less dangerous to others
- within 1-2m. –> M. tuberculosis multiplying slowly in macrophages is destroyed - Pyrazinamide
- within 4m. –> M.tuberculosis is destroyed, but mycobacteria transitioning to a semi-dormant phase are almost unaffected
Treatment
-1st line drugs (5)
Isoniazid (H) - 5mg/kg Rifampicin (R) - 10mg/kg Etambutol (E) - 15mg/kg Streptomycin (S) - 15m/kg --> not used anymore because there are too many adverse effects Pirazinamid (Z) - 25mg/kg
Phase 1 drugs
Intensive phase
2(3) HRZE
Phase 2 drugs
Continuation phase
4(7) HRE
Which drugs are pregnancy, childbirth, and lactation safe?
H, R, E
Which drugs are renal failure safe?
H, R
Other treatments
- glucocorticoids –> especially in pleurisy
- nutrition doesn’t play such a big role
- first TB treatment and then cancer treatment
Latent tuberculosis
- when a person is infected but does not have active tuberculosis
- positive tuberculin and IGRA test but no clinical, radiological or bacteriological evidence of the disease
Latent tuberculosis
-diagnosis
- asymptomatic and not contagious
- x-ray
- Tuberculin test –> Mantoux (more than 5mm is positive)
- if tuberculin test is negative then –> IGRA test (blood test - measure interferon-gamma produced by lymphocytes) and QuantiFERON test (measure ING-g concentration)
Latent tuberculosis
-treatment options
Preferred regimens
- Isoniazid PLUS rifapentine weekly for 3 months
- OR rifampin daily for 4 months
- OR isoniazid PLUS rifampin daily for 3 months
Alternative regimen:
-isoniazid daily for 6 or 9 months
