Tuberculosis Flashcards
By how much is the worldwide TB incidence rate falling by what percentage per year
About 2%
TB deaths have fallen by what percentage since 2000
29%
How many people are estimated to by infected by TB worldwide
2 billion
Examples of countries with high prevalence of TB
India, China, Indonesia, Philippines, Pakistan, Nigeria, Bangladesh, South Africa
Number of TB deaths per year
Around 1.6 million
Is TB more common in men or women
Men by 2x
Vulnerable groups to TB in the UK
People from high prevalence countries HIV positive Immunosuppressed Elderly and neonates Diabetics Those with chaotic lifestyle (1 in 10)
Mycobacteria causing TB present in
Soil and water
Examples of bacteria that cause TB
M. tuberculosis
M. africanum
M. bovis
Problem with culturing bacteria
Very slow growing - long wait to make diagnosis
Features of mycobacteria causing TB
Non-motile
Slow growing
Aerobic
Very thick fatty cell wall - causes resistance
Transmission of TB
Airborne
Exceptionally, M. Boris can be spread by
Consumption of unpasteurised infected cows’ milk
Immunopathology of TB
T cell mediated - eliminates mycobacteria but also results in tissue destruction.
Macrophages, epithelioid cells, laghan’s giant cells -> granuloma
3 fates of primary infection
Progressive disease
Contained latent
Cleared cured (immune memory)
Mycobacteria is spread via
Lymphatic system to draining hilarious lymph nodes
Primary TB can progress to
Tuberculosis bronchopneumonia
Milliary TB
Tuberculosis bronchopneumonia
Primary focus enlargement
Enlarged hilar lymph nodes compress bronchi - lobar collapse
Enlarged lymph node discharge into bronchus
Poor prognosis = high mortality
Miliary TB
Hematogenous spread of bacteria to multiple organs
Widespread small granulomata
Post primary disease hypothesis
TB bacteria entering a dormant stage
Balanced stage of replication and destruction by immune mechanisms
Clinical presentation of TB
Cough
Fever
Night sweats
Weight loss
Classical post-primary TB x-ray presentation
In the apices, fluffy/nodular upper zone, cavitation (10-30%)
When to consider CT scan
Normal chest x-ray but clinical suspicion Miliary TB Cavitation and other differential Lymphadenopathy, alternative diagnosis Targets for BAL
Primary TB x-ray presentation
Pneumonic lesion with enlarged hilar nodes - pleural effusion, mediastinal lymphadenopathy, miliary
Sampling bacteria methods
Sputum Induced sputum Bronchoscopy with BAL Endobronchial ultrasound with biopsy Lumbar puncture in CNS TB Urine in urogenital TB Aspirate/biopsy from tissue
Clinical mamagement - TB drugs
Isoniazid Pyrazinamide Rifampicin Ethambutol Streptomycin
Rules of TB treatment
Multiple drug therapy
Single agent treatment leads to resistance
Therapy for 6 months
TB therapy job for committed specialists only
Legal requirement to notify all cases
Test for HIV, Hep B and C
Standard treatment for TB
4 drugs for 2 months then 2 drugs for 4 months (4:2/2:4) Standard 12 tablets per day Pyridoxine with isoniazid Steroids Vitamin D substitution
Side effects of rifampicin
Orange ‘Irn Bru’ urine/tears/lenses
Hepatitis
Induces liver enzymes
All normal hormonal contraceptive methods ineffective
Side effects of isoniazid
Hepatitis
Peripheral neuropathy
Side effects of pyrazinamide
Hepatitis
Gout
Side effects of ethambutol
Optic neuropathy
BCG vaccination is
Given selectively to groups
Groups that are given BCG vaccination
Neonates or unvaccinated children under 5 whose parents/grandparents born in TB prevalent country
Unimmunised contacts of cases
Unimmunised high risk employees
BCG vaccination most effective when given to
Neonates
BCG vaccination is ineffective over the age of
16
Latent TB screening
Contacts of people with active pulmonary or laryngeal TB aged <65
New entrants from high epidemic areas
Outbreaks
Pre-biologics
Asymptomatic, normal chest x-ray and positive tests
Treatment of latent TB
Rifampicin and isoniazid for 3 month, or one alone for 6 months
Rifapentine and isoniazid once weekly for 13 weeks (chaotic lifestyle)
