Session 7 - TB Flashcards
What was the biggest advance in TB treatment in the 1900’s?
• Development of the BCG vaccine
Where is TB most prevalent?
• India and China
What area has the highest incidence of TB?
Subsahran Africa
Outline two usual treatments of TB
- Thoracoplasty (crushing of the chest, reduces area for TB to thrive)
- Exercise
Phrenic nerve crush - Paralyzed diaphragm, reduces ability of lung to expand
What does the BCG vaccine prevent?
• Childhood TB
Why are Mycobacteria hard to stain?
• Lipid-rich cell wall that retains some dyes, and resists decolourisation with acid
What is TB latency?
- First encounter may not cause disease
* Mycobacterium lives in system, can be reactivated spontaneously or as a result of a new encounter
When is risk of developing TB greatest after initial infection?
- First 2 years - 5%
* Rest of lifetime - 5%
What are the two main stages of tuberculosis infection?
- Primary complex
* Post-primary infection
What is the primary complex in TB?
• Infection begins with local scarring
What is post primary infection of TB?
- Refers to development of TB beyond the first few weeks
* Infection may spread throughout the body via blood (miliary spread) or develop into localised infection (meningitis)
Outline the pathology of TB infection
- Mycobacterium Tuberculosis phagocytosed
- Escapes from phagolysosome to multiply in the cytoplasm
- Causes intense immune response, which damages lung
How does intense immune response damage the body?
- Local tissue destruction - Cavitation in the lung
* Cytokine mediated systemic effects - Fever and weight loss
Why are the symptoms of late stage TB so varied?
Can effect every organ in the body, mimicking inflammatory and malignant disease
Give five main structures which can be affected by TB
- Pulmonary tuberculosis
- Tuberculous meningitis
- Lymph node tuberculosis (Often painless, most commonly in non-asians)
- Kidney infection
- Lumbosacral spine
- Inflammation of large joints
Give some symptoms of pulmonary tuberculosis
- Chronic cough
- Haemoptysis
- Fever
- Weight loss
- Recurrent bacterial pneumonia
What does tuberculous menigitis present with?
- Fever
* Slowly detriorating level of conciousness
What are the symptoms of kidney infection with TB?
- Signs of local infection
- Fever
- Weight loss
- Ureteric fibrosis
- Hydronephropathy
What are the two main symptoms of lumbosacral spine infection with TB?
- Vertebral collapse
* Nerve compression
What can inflammation of the large joints due to TB cause?
• Destructive arthritis
Outline what occurs after mycobacterium tuberculosis enters lung tissue in terms of immune response
- Ingested by macrophages, escapes from paholysosome to multiply in cytoplasm
- Immune response provoked via IL-12
- IL2 drives the release of IFN-y and TNF-a from Natural Killer and CD4+ T helper cells
- Cytokines activate and recruit more macrophages from the site of infection, resulting in formation of Granulomas
Give some primary changes in TB
- Few symptoms
* Lymph nodes often enlarge
Outline some post-primary changes in TB
• Cough (not always productive)
• Fever (towards the end of the day or at night)
Weight loss and general debility
What does chest x-ray of post primary TB cause?
- Patchy solid lesions
- Cativated solid lesions
- Streaky fibrosis
Flecks of calcification
Give six signs of respiratory TB
- Non-specific
- Pallor
- Fever
- Weight loss
- Clubbing
- Palpable lymph nodes
Give seven symptoms of respiratory TB
• Primary usually asymptomatic • Post Primary ○ Tiredness and malaise ○ Weigth loss and anorexia ○ Fever ○ Cough ○ Breathlessness
Haemoptysis
Give six x-ray changes in Respiratory TB
- Shadowing
- Cavities
- Consolidation
- Calcification
- Cardiomegaly
- Miliary seeds
Who is pleural TB more common in?
Males
Give two mechanisms by which pleural TB occurs?
• Hypersensitivity response in primary infection
• Tuberculosis epyema with ruptured cavited
○ Burrows through chest wall
What is lymph node tuberculosis?
• More common in children, women and Asians. Painless, occurs most commonly in the neck
What are two types of osteo-articular TB?
- Tuberculous Spondylitis
* Poncet’s disease
What is tuberculosis spondylitis?
- Most common form of osteoarticular TB
- Starts in sub-chondral bone and spread to vertebral bodies and join space, before following the longitudinal ligaments anterior and psoterior to the spine
- Mainly occurs in the lower thoracic and lumbar spine and can be very high
What is poncet’s disease?
• Aseptic polyarthritis
Knees, ankles and elbows
What is miliary tuberculosis?
• Bacili spread through blood stream during primary infection of reactivation
• Lungs are always involved
○ Spread throughout both lungs, as it is in the blood
○ Many visible through the lungs on an x-ray
Give four symptoms of miliary tuberculosis
- Headaches which suggest meningeal involvement
- Few respiratory symptoms
- Ascites may be present
- Retinal involvement in children
What are the three factors which need to be investigated to give a TB diagnosis?
- Clinical features
- Radiological features
- Microbiology
Give three of the main clinical features of TB
- Cough
- Night fever
- Weight loss
What are five main radiological features of TB?
- Shadowing
- Cavities
- Consolidation
- Cardiomegaly
- Miliary seeds
What does microbiology need to achieve in order to diagnose TB?
- Identification of bacillus
- Direct smear and subsequent culture of the appropriate body fluid
- Important to isolate organism and determine it susceptibility to drugs
Outline treatment of patients with TB
- Initially treated with four drugs for 2 months
* 2 drugs are then dropped, and the other two continue to be used to treat
Why are multiple drugs used in TB?
• To combat resistance (5-10% patients TB resistant to isoniazid)
Why are there problems with compliance, and what can be done to solve these problems?
• Long drug regime with several different pills to take
Patients instead put on directly observed therapy
What does directly observed therapy do?
• Increases adherence to antibiotic treatment
What are four drugs given in the initial phase of TB treatment?
- Riampicin
- Isoniazid
- Pyrazinamide
- Ethambutol
What are the two drugs given in the continuation phase of TB treatment?
- Rifampicin
* Isoniazid
Give six side effects of rifampicin
- Hepatitis
- Rash
- Flu-like symptoms
- Shock
- Acute Renal Failure
- Thrombocytopenic purpura
What three side effects of pyrazinamide
• Rash, hepatitis, athralgia
Give a side effect of ethambutol
• Optic neuritis
Describe the mechanism of multidrug-resistant TB
- Caused by incompleted treatment
- Residence in a country with a high incidence of MDRTB
- Failure to response clinically to an adequate regimen
How is multidrug resistant TB treated?
• A grueling regimen of several drugs at once
What is the BCG vaccine?
- Attenuated Live Bovine Tuberculosis Bacillus
* Bacteria retain a strong enough antigenicity to act as a vaccine for human TB
What are two issues with BCG?
- Has variable efficacy depending on genetic variation of population and BCG strain
- Efficacy lasts 15 years at most
What were UK regulations on vaccination up to 2005?
- All children ages 13 were immunised along with all neonates born into high risk groups
- Now only high risk groups given, as cost effectiveness has fallen due to falling incidence rates of TB
Give five groups which are at risk of TB
- HIV patients
- Those suffering from malnutrition
- People living in overcrowded accommodation
- IV drug abusers
- Smokers
- Diabetics
- Asians
What is the link between HIV and TB?
- Much more likely to develop TB if already have HIV
- Risk estimated to be 20-37 times greater in HIV infected people than uninfected people
- Leading cause of morbidity and mortality among HIV patients
Describe what occurs when a case of TB is suspected
- Contact is immediately made with TB radiology
- Patient goes straight to TB clinic and given a questionnaire and asked to give sputum samples
- Treatment within 7 days
