TB Flashcards
What pathogen causes TB?
mycobacterium tuberculosis
Pulmonary TB symptoms
persistent cough
weight loss
pyrexia (can be worse at night)
failure of antibiotic therapy
haemoptysis
Extrapulmonary TB symptoms
depends on location
bone = pain at site
bowel = abdominal pain
nodal = swelling at site, pyrexial
CNS = focal neurology, headache
endometrial = amenorrhoea
TB risk factors
ethnic minority groups
homeless
drug + alcohol abuse (associated with overcrowding, poor living conditions and malnutrition)
close contact with infected patient
immunosuppression
young or old age
What would be seen on biopsy in TB?
caseating necrotising granuloma
Describe how a sputum sample is collected and tested for TB?
3 morning samples
Ziehl-Neelsen staining (acid-fast bacilli staining)
Typical drug regime for TB
Rifampicin, Isoniazid, Pyrazinamide, Ethambutol x2 months
then Rifampicin/isoniazid x4 months
What is MDR-TB?
multidrug-resistant TB
resistant to Rifampicin and Isoniazid
How is MDR-TB diagnosed?
culture of organism
DNA probe to check for Rifampicin + Isoniazid resistance
How is contact tracing carried out for TB?
household contacts in all cases of pulmonary TB
<65 = Tuberculin test
>65 = CXR
Who is screened for TB?
HIV patients
patients on immunosuppressant drugs eg. biologics
occupational health screening eg. healthcare workers
Describe Tuberculin testing
purified protein derivative of TB
intradermal injection
mantoux single intradermal injection
indicates immune recognition of TB
Describe IGRA for TB screening?
Interferon gamma releasing assays
IFN-Y released from primed T-lymphocytes when exposed to Tuberculin specific proteins
T-spot test
Qwantiferon-Gold test
not used for active case diagnosis
What is latent TB? What tests will be +ve?
+ve Tuberculin test
+ve IGRA test
no evidence of active TB )eg. on CXR)
5-10% lifetime risk of active TB
How is latent TB treated?
Rifampicin/Isoniazid or Isoniazid monotherapy
How can TB be prevented?
seek out latent cases and treat
BCG vaccine (universal or selective)
What does BCG stand for in BCG vaccine?
bacille calmette-guerin
Describe BCG vaccination
intradermal vaccine
effective in children (prevents TB meningitis)
Who is given the BCG vaccine in the UK?
targeted in areas where rate => 40/100000 where family born
given at birth (up to 4-6 weeks)
nonName some atypical mycobacteria
M. Kansasii
M. Malmoense
M. Avium Intercellulare
M. Cheloneii
M. Marinum
M. Scrofulae
M. Abscessus
(also called non-tuberculous mycobacteria)
What are some differences between TB and atypical mycobacteria?
non-tuberculous mycobacteria has:
- prolonged treatment
- lower cure rate, higher relapse rate
- non-notifiable
- diagnosis = 2 +ve sputum samples`
Isoniazid side effects
peripheral neuropathy (pyridoxine given to prevent this)
liver toxicity
Rifampicin side effects
liver toxicity
hepatic enzyme (p450) inducer
turns bodily fluids red/orange colour
Ethambutol side effects
visual disturbance (colour blindness, loss of acuity etc)
avoid in chronic kidney disease
Pyrazinamide side effects
liver toxicity
Second line TB treatments (in drug-resistant cases)
amikacin
macrolides
quinolones
capreomycin
