Tuberculosis Flashcards
What is the 2nd leading cause of death from an infectious disease worldwide?
TB
What factors increase the likelihood of TB contraction?
Poor access to BCG and TB drugs
Overcrowding e.g. cities, prisons
Poor nutrition
Areas of high moving populations
List some high incidence areas of TB
South east asia
Africa
Russia
South America
List some high incidence areas of TB in the UK
London
Glasgow
Birmingham
What organism is responsible for TB?
Mycobacterium tuberculosis Mycobacterium bovine (in cows)
Describe some Mycobacteria spp that cause diseases other than TB
M. avium intracellulare
M. kansasii, M. malmoense, M. xenopii
M.leprae
Describe the organisms responsible for TB
Mycobacterium, acid and alcohol fast bacilli
Non motile slow growing aerobic bacilli Unusual very thick cell wall made up of: - lipids - peptidoglycans - arabinomannans
Resistant to acid, alkali and detergents
Resistant to neutrophils and macrophages
What stain is used to identify TB?
Ziehl Neilson strain for AAFB organisms
Aniline based red dyes stick to cell wall
How is TB transmitted?
M. tuberculosis is airborne, and able to survive for very long periods though is eliminated by UV radiation and dilution
M.bovine is ingested from infected cows milk and deposited in cervical and intestinal lymph nodes
Describe the immunopathology of TB
APC recognises TB, presents in LNs Cells migrate to site of infection Macrophages/epitheloid cells fuse to form Langhans giant cells These compartmentalise infections Central caveating necrosis
What T cell is responsible for TB destruction?
Th1
Why is the Th1 response a double edged sword?
Reduces number of mycobacterium
Causes tissue destruction
Describe primary infections of TB
Usually children Travels in lymphatics to all over body Settles in hilar lymph nodes Erythema nodosum Primary complex - lesion + enlarged LN Ghon focus - calcified scar of lesion
Describe the basis of tuberculin tests
Intradermal administration of tuberculoprotein (PPD) resulting in inflammation and induration after 48hrs if patient has had previous exposure to TB
What is the name of tuberculin tests?
Mantoux/Heaf
Describe the effects of disease progression following primary infection
Primary focus enlarges to form cavities Enlarged hilar LNs compress bronchi Discharge secreted into bronchi Lead to persistent productive cough Tuberculous pneumonia
What causes secondary disease?
Re-activation of latent disease
Re-infection
What systems does TB affect?
Pulmonary Los Bone and joints Genitourinary Infertility Pericardium : constrictive pericarditis Abdomen: ascites Adrenal: addisons disease Skin: lupus vulgaris
List some respiratory symptoms of TB
Cough Sputum Haemoptysis Pleuritic pain SOB
List some systemic symptoms of TB
Malaise
Fever
Weight kiss
Night sweats!!!
List some important PMH relevant to TB
DM
Immunosuppressive disease
previous TB
List some drugs related to TB
Immunosuppressive drugs
List some aspects pf personal social history relevant for TB
Alcoholism
IVDA
Poor social circumstances
Living in poor overcrowded area
List some signs only seen in advanced disease
Crepitations - crackles
Bronchial breathing
Clubbing
List some conditions that would suggest high index of suspicion for TB
Immunosuppressed eg. HIV, corticosteroids Malnutrition Alcoholism Vagrants Previous gastric surgery Malignancy DM Adolescence/elderly Recent immigrants from high risk areas
What investigations are used for TB?
3 sputum collections over 3 days for: - Ziehl Neilson stain - 8 week culture - sputum PCR CXR - bilateral shadows on apices, calcified CT of thorax Bronchoscopy with bronchoalveolar lavage Pleural aspiration and biopsy in effusions
List the possible surgical options for TB
Phrenic crush Artificial pneumothorax Pneumoperitoneum Thoracoplasty Lung resection
What is the current drug therapy for TB?
For 2 months: - Rifampicin - Isoniazid - Ethambutol - Pyrazinamide For next 4 months: - Rifampicin - Isoniazid
When are TB patients determined to be non-infectious?
2 weeks later
What are some side effects of rifampicin?
Orange bodily secretions Induces liver enzymes: - prednisone - anticonvulsants - oral contraceptive Hepatitis
What are some side effects of isoniazid?
Hepatitis
Peripheral neurpathy
What are some side effects of Ethambutol?
Optic neuropathy
What are some side effects of pyrazinamide?
Gout
When screening for TB in person <16yo with no BCG, how do you proceed?
Tuberculin test
If positive
What in addition to chemotherapy should be carried out after diagnosing TB?
Screening
HIV test if from HIV prevalent country
