Tubersculosis Flashcards
What is Tuberculosis?
-Bacterial infection spread through
State the types of myobacteria
-M.tuberculosis, M.africanum, M.bovis , non-tubersculosis myobacteria, NTM infections/Atypical mycobacteria, M.leprae(leprosy)
What type of bacteria is myobacteria? State the stain used
- bacillus, aerobic + thick fatty cell wall
- AAFB ( not all are TB)
- Ziehl Nielson stain
Resistance of myobacteria
-resistant to acids, alkalis + detergents, neutrophil + macrophage destruction
How is TB spread?
- inhalation
- pulm + laryngeal TB spreads
- M.bovis spread by consuption of unpasteurized infected cows milk
Describe the mechanism of TB
Activated macrophages > epithelioid cells > Langhan’s giant cells
Accumulation of macrophages, epithelioid+Langhan’s cells
> GRANULOMA
The Th1 cell mediated response reduces number of invading mycobacteria
Macrophages defence to TB is poor and will end up destroying tissue - caseating necrosis
Describe primary infection of TB
- spreads via lymphatics to draining hilar lymph nodes
- no symptoms; fever/malaise.
- Erythema, nodosum
- Initial lesion + local lymph node ( primary complex)
- fibrosis + calcification
What conditions can primary infection lead to?
- TB bronchopneumonia
- Granuloma and caseous necrosis - ghon focus ( cavitation)
- enlarged hilar lymph compresses bronchi, lobar collapse
- enlarged hilar lymph node discharges into bronchus
- Systemic miliary TB which id the spread of TB to multiple organs
What is Post primary disease
- TB bacteria enters dormant stage with low/no replication over long period of time
- balanced state of replication + destruction by immune mechanisms
Presentation of TB
-cough
-fever
-sweats
-weight loss
CRP normal in 15%, ESR normal in 21%
Diagnosing active pulmonary TB (post-primary, reactivated)
CXR:
- apices soft/fluffy, cavitation
- Lymphadenompathy(rare)
- normal CXR (13% cases, HIV)
When to consider CT in post-primary TB ( reactivated)
- normal CXR
- mililary TB
- cavitation + other differential
- lymphadenopathy
- targets for BAL
Diagnosing primary TB
CXR:
- mediastinal lymphadenopathy
- pleural effusion
- miliary
-pneumonic lesion + enlarged hilar nodes = primary TB
Investigation of TB
- sputum sample ; 8-24hr gap + at least 1 morning sample
- induced sputum
- bronchoscopy with BAL
- endobronchial ultrasound(EBUS) with biopsy
- lumbar puncture in CNS TB
- Urine in urogenital TB
- Aspirate/biopsy from tissue ( lymph node, bone, joint, brain, abscess)
- matoux or IGRA NOT used for diagnosing active TB
Treatment of TB
- multiple drug therapy due to resistance within 14 days
- must occur for 6 months minimum
- Legal requirement to notify all cases
- test for HIV, HepB, HepC
PMH and SH risk factors of TB
PMH:
- immunosuppresion( HIV/AIDS, corticosteroids, anti-rejection meds)
- diabetes
- gastric surgery
- malignancy
SH
- vagrant/homeless
- IVDA
- alcoholism
- malnutrition
- from high incidence area
Treatment of TB - state drugs used
- rifampicin, isoniazid(taken with pyridoxine B6 to reduce neuropathy), pyrazinamide, ethambutol
- RIPE
Steroids: ( CNS, milliar, pericardial
-6month course of treatment; all 4 for first 2 months, rifampicin and isoniazid for last 4 months
Side effects of drugs
Rifampicin:
- orange urine/tears/lenses
- induces liver enzymes; prednisolone, anticonvulsants
- horemonal contraceptive ineffective
- Hepatitis
Isoniazid
- hepatitis
- peripheral neuropathy ( pyroxidine b6)
Pyrazinamide
- hepatitis
- Gout
Ethambutol
-optic neuropathy
All 4 can cause rash
BCG vaccine
-neonates, unvaccinated children >5yrs
Latent TB (LTBI) - screeening and treatment
Screen
- contacts of people with active pulmonary/laryngeal TB ages <65yrs (hepatoxicity increases with age)
- ‘pre biologics’ TNF-alpha inhibitors
Asymptomatic with normal CXR/examination and +ve:
-mantoux skin test, interferon gamma release assay(IGRA)
Treatment of LTBI(need to rule out active TB)
- Rifampicin + isoniazid for 3 months or
- isoniazid only for 6 months or
- rifampicin for only 6b months or
- rifapentine + isoniazide weekly for 12 weeks (underserved population)
-Describe the global districbution of TB + its impact on TB in the UK
- High incidence in:
- sub-saharan africa
- s. asia(china/india)
Within UK high incidence in:
-London, birmingham
Vulnerable groups in UK - TB
HIV/AIDS, immunocompressed, elderly, neonates, diabetics(likely to get infection)
-homeless, alcoholics, IDU, mental health problems
