Tuberculosis Flashcards
how is TB distributed in the UK?
• it is more common in more deprived areas of the world?
What is happening to the TB incidence worldwide?
• it is reducing
2/3 of TB cases are found in how many countries?
• 8 countries
Where are most of the cases of TB found in the UK?
• London (clusters in cities)
What groups are vulnerable to TB?
• People from high prevalence countries, HIV positive, Immunocompromised, Elderly, Neonates, Diabetics, Homeless, Alcohol dependency, IV drug use, Mental health problems, prisoners
What is the characteristic of TB?
• It is non motile, it is very slowly growing and it is aerobic, uniquely has a very thick fatty cell wall (resistant to acids, alkalis, detergents, neutrophil and macrophage destruction)
How does TB spread?
• Airborne, someone with TB bacteria in their lungs coughs, TB bacteria attached to aerosol droplets which can remain suspended in air for many hours, especially if there is poor air circulation, someone breathes this bacteria in, requires prolonged close contact.
How is TB not spread?
• Shaking hands, sharing food, touching surfaces, sharing toothbrushes, kissing
What is the primary infection of TB?
• no preceding exposure or immunity, Mycobacteria spread via lymphatics to draining hilar lymph nodes. Usually no symptoms, can be fever, malaise
What are the three outcomes of primary infection?
• Progressive disease - ineffective immune response from the patient, Contained latent - activates when the patient becomes immunocompromised, Cleared + cured
What happens during progressive disease after primary infection?
• Primary infection prgresses to TB bronchopneumonia, primary focus continues to enlarge, enlarged hilar lymph nodes compress bronchi, lobar collapse, enlarged lymph nodes discharged into bronchus, poor prognosis
What happens in post-primary disease?
• TB bacteria enetering a dormant stage with low or no replication over prolonged periods of time, Balnced stage of replication and destruction by immune mechanisms
What are the main clinical presentations of TB?
- Cough
- Fever
- Sweats
- Weight loss
- All three symptoms
How to identify TB?
- Sputum; 3 samples, 8-24hr gap, at least 1 morning sample
- induced sputum
- Bronchoscopy with BAL
- Endobronchial ultrasound with biopsy
- lumbar puncture in CNS TB
- Urine in urogenital TB
- Aspirate/biopsy from tissue (bone, lymph node, joint, brain, abscess)
What are the drugs used for TB?
• Isoniazid, Pyrazinamide, Rifampicin, Ethambutol
Immunosupressive drugs
What are the rules for TB treatment?
- multiple drug therapy is essential (single treatment leads to drug resistant organisms within 14 days)
- Therapy must continue for at least 6 months
- TB therapy is a job for committed specialists only
- Legal requirement to notify all cases
- Test for HIV, Hepatitis A, B and C
What are the main side effects of treatment for TB?
- hepatitis
- rash
- Rifampicin - ornage irn bru urine, tears, lenses, induces liver enzymes, all hormonal contraceptive methods ineffective
- Isoniazid - Peripheral neuropathy
- Pyrazinamide - Gout
- Ethambutol - Optic neuropathy
What is the microorganism responsible?
Mycobacteria
What are the other mycobacterium that don’t cause tb?
Mycobacteria other than tuberculosis (MOTT) (about 30% of UK isolations)
Mycobacterium avium-intracellulare (HIV)
M. kansasii, M. malmoense, M. xenopii
Mycobacterium leprae leprosy
What removes mycobacteria outdoors?
UV radiation and infinite dilution
Which type of droplet nuclei impact in the alveoli and slowly proliferate?
Small nuclei, Larger droplet nuclei impact on large airways and cleared
How is infection of mycobacterium bovis spread?
Consumption of infected cows’ milk
- deposited in cervical, intestinal lymph nodes
What stimulates the macrophages to become activated?
Th1 helper cells from the lymph node, these Th1 cells are activated by antigen presenting cells.
These Th1 cells after receiving the signal from the antigen presenting cell then clonially proliferate in the lymph node
What are Th1 cells?
Type 1 T helper (Th1) cells produce interferon-gamma, interleukin (IL)-2, and tumour necrosis factor (TNF)-beta, which activate macrophages and are responsible for cell-mediated immunity and phagocyte-dependent protective responses.
Which specific chemical activates macrophages?
Interferon gamma CD40 - which is produced by Th1 cells in the lymph node
What is the result of activated macrophages?
Damaged epithelioid cells
Langhan’s giant cells
Accumulation of macrophages, epithelioid & Langhan’s cells GRANULOMA
Central caseating necrosis (may later calcify)
What disease is caseus necrosis usually indicative of ?
TB
What is meant by the 2 edged sword of the Th1 cell mediated immunological response?
Eliminates / Reduces number of invading mycobacteria
Tissue destruction is a consequence of activation of macrophages
What is the pathology for a resistant and susceptible host?
Tissue destruction
Organism contained
Disease
Who is normally affected by the primary infection?
Usually children, 80% Infected focus in alveolus, (lymph nodes, gut)
Where do mycobacteria spread to once they are in the alveoli?
Spread via lymphatics to draining hilar lymph nodes
Then there is haematogenous seeding of mycobacteria to all organs of the body (lung, bone, genitourinary system)
What is the mantoux test?
Injection of tuberculin into the transdermal layer of skin. After 48-72 hours amount of induration present can identify possible health problems.
What is responsible for the induration in the mantoux test?
Intra dermal administration of tuberculoprotein (PPD - Purified protein derivative) results in lymphocytic and macrophage based area of inflammation/induration after 48 hours
how does TB affect the CSF and the pleura?
Can cause meningeal TB (severe, CSF high protein, lymphocytes)
AND
Tuberculosis pleural effusion
What are the sites of post primary disease from TB?
Pulmonary disease
Lymph nodes, usually cervical
Bone and joint; spine, hip, etc
Genito-urinary; kidney, ureter, bladder
Males; infertility - vas deferens
Females; infertility - uterus, Fallopian tubes
Pericardium; constrictive pericarditis
Abdomen; ascites, ileal TB ® obstruction
Adrenal ® Addison’s disease
Skin; lupus vulgaris
Just about any other tissue!
What are the features of TB usually after 6-12 months?
Miliary , meningeal, pleural TB
What are the features of TB after 1-5 years?
Post primary disease - pulmonary and skeletal
What are the features of TB after 10 years?
Genitourinary, Cutaneous T
What are the symptoms for Post primary TB?
Respiratory; cough, sputum, haemoptysis, pleuritic pain or breathlessness
Systemically unwell
malaise, fever, weight loss (“night sweats”) - very characteristic of TB
What is characteristic PMH for Post-primary Pulmonary Tuberculosis?
Diabetes, Immunosuppressive diseases, Previous TB
What is the PSH for post primary pulmonary TB?
Alcohol – poor nutrition, immune system is suppressed, IVDA (intravenous drug users? Immnue system suppressed), poor social circumstances, Immigrants from high incidence areas
What are the signs for Post-primary Pulmonary Tuberculosis?
May be none at all - extensive TB can be present without physical signs!
If more advanced, may be crackles, bronchial breathing.
Finger clubbing is rare unless very chronic infection
What are the means of diagosing TB?
Sputum analysis
Chest radiograph
CT scan of thorax
Bronchoscopy with alveolar lavage, transbronchial biopsy
Pleural aspiration and biopsy if peural effusion
How do we analyse sputum samples for TB?
ZN stain - immediate answer if AAFB
Culture
Sputum PCR
What features of a chest radiograph confirms presence of TB?
Patch shadowing, often in apices/upper zones, or apex or lower lobes
Cavitation
Calcification if chronic or healed TB
What happens after the fluid is collected from the pleural aspiration?
FLuid cytology (lymphocytes)
Fluid for AAFB and culture
Biopsy histology
1 biopsy sent in Saline for culture
What is treatment of tuberculosis?
Vitamin D causes macrophages to release Cathelecidin which is a very potent antibiotic.
Surgery - Collapse of the cavity by: Phrenic crush (crushing the phrenic nerve causes the diaphragm on that side to become paralysed and rise up, closing the cavity), artificial pneumotorax (collapses the lung and therefore the cavity), pneumoperitoneum, thoracoplasty (Six to eight ribs were broken and pushed into the thoracic cavity to collapse the lung beneath), lung resection (removal of a segment of lung).
How are drugs used against TB?
Multiple used to prevent resistant organisms forming,
Therapy at least 6 months, slowly growing organism
ONLY SPECIALISTS TREAT
Likelihood of infection with TB depends on?
Duration of contact
Intensity of infection
How do you screen for TB using tuberculoprotein?
If younger than 16 and no BCG there should be no immunity to Tuberculoprotein
What other test besides the mantoux test can determine the presence of TB?
Heaf test
How would you treat a patient who is heaf positive (2-4) exposed to TB?
If their X-ray is normal they are at risk of disease (miliary, or meningeal)
Chemoprophylaxis to kill mycobacteria
Rifampicin + Inh (isoniazid) 3 months
Inh 6 months
If their X-ray is abnormal - Treat as primary TB
What should you do 6 weeks after a heaf negative result?
2nd heaf test
If it is negative - BCG
If it is positive - follow procedures with a chest X-ray and follow up procedure
If older than 16 with an abnormal chest X-ray?
Investigate for TB and treat if necessary
