Lecture 10 - Tuberculosis Flashcards
What demographics are at risk of developing TB?
Non-UK born (south Asia and sub-Saharan Africa
HIV + other immunocompromising conditions
Homelessness
Drug use
Prisoners
Close contacts of TB
Young people and old
What are the 2 most common species of bacteria causing Tuberculosis in the Mycobacterium family?
Mycobacterium tuberculosis
Mycobacteria bovis (TB in cattle and humans)
What type of bacteria are mycobacterium ?
Non motile Rod shaped (bacilli)
Obligate aerobe
What structural features of the mycobacterium (bacilli) make it difficult for the body to eliminate?
Long-chain fatty acids with glycolipids in the cell wall:
-structural rigidity
-acid alchol fast meaning they don’t stain
Replicate slowing
How is TB transmitted?
Respiratory droplets via coughing and sneezing
What is the infectious dose for TB infection?
Only 1-10 bacilli needed
How easily can TB infection be acquired?
Highly contagious but not easily acquired
Need prolonged exposure and close contact
What settings is TB infections common?
Schools
Provisions
Families
What is the pathogenesis of TB?
Inhaled bacteria
Bacilli engulfed by alveolar macrophages (TB infection)
Drain to lymph nodes
Can then progress to active Primary disease or bodies T cells surroud and contain the infection causing latent infection
What can then happen once the TB infection has become a latent infection?
Body heals and eliminates
Reactivation leading to symptomatic Post Primary TB
What are the risk factors for reactivation of contained TB to Post primary TB?
Anything that compromises the immune system:
HIV
Substance abuse
Immunosuppressive therapy
TNFa antagonists
Organ transplant
Silicosis
Haematological malignancy
How does Primary TB infection differ to Latent TB infection?
Primary TB:
Active multiplying tubercle bacilli
CXR abnormal
Symptomatic (cough, fever and weight loss)
A case of TB
Sputum smears and cultures maybe positive
Latent TB infection:
Inactive non multiplying tubercle bacilli
CXR normal
Non symptomatic
Sputum smears and cultures negative
NOT a case of TB
Where is the main site of TB infection?
Pulmonary TB (lungs)
What sort of patients is extra pulmonary TB often seen in?
HIV infected or immunosuppressed patients
Young children
What is Miliary TB?
Where the TB disseminates all over the body through the blood
What histological changes occur in TB?
Ceseaous necrosis/granulomas
Where T lymphocytes/macrophages surround bacilli
Look at the xray of a patient with TB on slide 19
What are some symptoms of pulmonary TB?
Cough
Haemoptysis
Fever
Night sweats
Weight loss and anorexia
Tiredness and malaise
What investigations would be done with pulmonary TB?
CXR (when the primary TB damages lungs))
Microbiology stamps
Histology of lymph nodes
What are some radiological findings with TB infection?
Consolidation often at upper apex/lobes
Cavitation in the consolidation
Ill defined and patchy
Look at the last slide at the first x-ray what is this showing?
Pleural effusion with a TB infection
What is the main staining method to diagnose TB?
What is the problems with it?
Ziehl-Neislon stain (but its not very sensitive)
Cant differentate between MTB and NTM and live or dead organisms
What is the gold standard for TB diagnosis?
TB culture
How can TB then be identified from a culture?
Whole genome sequencing
Drug susceptibility
