Tubersculosis

Question 1

What is Tuberculosis?

Answer 1

-Bacterial infection spread through

Question 2

State the types of myobacteria

Answer 2

-M.tuberculosis, M.africanum, M.bovis , non-tubersculosis myobacteria, NTM infections/Atypical mycobacteria, M.leprae(leprosy)

Question 3

What type of bacteria is myobacteria? State the stain used

Answer 3

• bacillus, aerobic + thick fatty cell wall
• AAFB ( not all are TB)
• Ziehl Nielson stain

Question 4

Resistance of myobacteria

Answer 4

-resistant to acids, alkalis + detergents, neutrophil + macrophage destruction

Question 5

How is TB spread?

Answer 5

• inhalation
• pulm + laryngeal TB spreads
• M.bovis spread by consuption of unpasteurized infected cows milk

Question 6

Describe the mechanism of TB

Answer 6

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

Question 7

Describe primary infection of TB

Answer 7

• spreads via lymphatics to draining hilar lymph nodes
• no symptoms; fever/malaise.
• Erythema, nodosum
• Initial lesion + local lymph node ( primary complex)
• fibrosis + calcification

Question 8

What conditions can primary infection lead to?

Answer 8

• 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

Question 9

What is Post primary disease

Answer 9

• TB bacteria enters dormant stage with low/no replication over long period of time
• balanced state of replication + destruction by immune mechanisms

Question 10

Presentation of TB

Answer 10

-cough
-fever
-sweats
-weight loss
CRP normal in 15%, ESR normal in 21%

Question 11

Diagnosing active pulmonary TB (post-primary, reactivated)

Answer 11

CXR:

• apices soft/fluffy, cavitation
• Lymphadenompathy(rare)
• normal CXR (13% cases, HIV)

Question 12

When to consider CT in post-primary TB ( reactivated)

Answer 12

• normal CXR
• mililary TB
• cavitation + other differential
• lymphadenopathy
• targets for BAL

Question 13

Diagnosing primary TB

Answer 13

CXR:

• mediastinal lymphadenopathy
• pleural effusion
• miliary

-pneumonic lesion + enlarged hilar nodes = primary TB

Question 14

Investigation of TB

Answer 14

• 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

Question 15

Treatment of TB

Answer 15

• 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

Question 16

PMH and SH risk factors of TB

Answer 16

PMH:

• immunosuppresion( HIV/AIDS, corticosteroids, anti-rejection meds)
• diabetes
• gastric surgery
• malignancy

SH

• vagrant/homeless
• IVDA
• alcoholism
• malnutrition
• from high incidence area

Question 17

Treatment of TB - state drugs used

Answer 17

• 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

Question 18

Side effects of drugs

Answer 18

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

Question 19

BCG vaccine

Answer 19

-neonates, unvaccinated children >5yrs

Question 20

Latent TB (LTBI) - screeening and treatment

Answer 20

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)

Question 21

-Describe the global districbution of TB + its impact on TB in the UK

Answer 21

• High incidence in:
• sub-saharan africa
• s. asia(china/india)

Within UK high incidence in:
-London, birmingham

Question 22

Vulnerable groups in UK - TB

Answer 22

HIV/AIDS, immunocompressed, elderly, neonates, diabetics(likely to get infection)

-homeless, alcoholics, IDU, mental health problems