Tuberculosis (TB) and the BCG vaccine Flashcards
What groups should receive the BCG vaccine in the UK
- infants living in TB prevalent areas
- infants with a parent/grandparent from a country where TB is prevalent
- contacts of a case of respiratory TB
- patients who were born/have lived in a TB prevalent country for at least 3 months
- healthcare workers
- prison staff
- those who work with homeless people
The TB vaccine is a live attenuated vaccine. TRUE/FALSE?
TRUE
contains live attenuated Mycobacterium bovis
Contraindications to a BCG vaccine
previous BCG vaccination
past history of TB
HIV
pregnancy
positive tuberculin test (Heaf or Mantoux)
Why is the BCG vaccine not given over the age of 35?
no evidence that it works for people of this age group.
Clinical features of Primary TB infection
- may be asymptomatic
- fever
- pleuritic pain (secondary to pleural effusion)
- retrosternal pain (secondary to enlarged bronchial lymph nodes)
Clinical features of secondary/reactivated TB
- cough
- productive haemoptysis
- weight loss
- fatigue
- night sweats
- fever
Treatment of active TB in initial phase (first 2 months)
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol
Continuation phase treatment in TB
Rifampicin
Isoniazid
Treatment of latent TB
3 months of isoniazid (with pyridoxine) and rifampicin
OR
6 months of isoniazid (with pyridoxine)
For how long are patients with meningeal tuberculosis treated
At least 12 months
(with steroids)
In what groups may you use Directly Observed Therapy (3 week dosing regimen)
- homeless people with active TB
- patients likely to have poor concordance
- prisoners with active or latent TB
Immune reconstitution disease typically occurs how long after starting TB treatment? How does it present?
- typically 3-6 weeks after starting treatment
- presents with enlarging lymph nodes
Adverse effects of rifampicin
potent liver enzyme inducer
hepatitis
orange secretions
flu-like symptoms
Adverse effects of Isoniazid
peripheral neuropathy
hepatitis
agranulocytosis
liver enzyme INHIBITOR
Adverse effects of pyrazinamide
hyperuricaemia (causing gout)
arthralgia
myalgia
hepatitis
How can isoniazid induced peripheral neuropathy be prevented?
pyridoxine (Vitamin B6)
Adverse effects of ethambutol
optic neuritis
Main technique used to screen for latent TB
Mantoux
in recent years an interferon-gamma blood test has been introduced
Describe how a mantoux test is carried out
0.1 ml of purified protein derivative (PPD) injected intradermally
result 2-3 days later
Size of induration 2-3 days following Mantoux test:
< 6mm
Negative
=> unvaccinated individuals may be given the BCG
Size of induration 2-3 days following Mantoux test:
6 - 15mm
Positive
- Should not be given BCG
- May be due to previous TB infection or BCG
Size of induration 2-3 days following Mantoux test:
> 15mm
Strongly positive
- Suggests tuberculosis infection.
What causes a false negative mantoux test
miliary TB
sarcoidosis
HIV
lymphoma
very young age (e.g. < 6 months)
CXR findings in active TB
- upper lobe cavitation (reactivated TB)
- bilateral hilar lymphadenopathy
Investigations used to diagnose TB
- Sputum smear (rapid)
=> Ziehl-Neelsen stain where all mycobacteria are stained (not very sensitive) - Sputum culture (takes weeks)
=> most sensitive - Nucleic acid amplification tests (NAAT)
Most common site for secondary TB
Lung
Sites of extra-pulmonary TB infection
CNS (TB meningitis)
vertebral bodies (Pott’s disease)
cervical lymph nodes
renal
gastrointestinal tract
