Tuberculosis Flashcards
Tuberculosis as a g_____ c______ disease, caused by m_____
granulomatous caseating
mycobacteria
What are the 4 species known as mycobacterium tuberculosis complex? (MTC that cause TB)
M. tuberculosis
M africanum
M microti
M bovis
Where does M bovis come from?
Unpasteurised milk
Where is TB most common?
South Asia (China, India, Pakistan)
Subsaharan Africa
Approximately how many people worldwide have TB? (mostly latent)
1.7 billion
How is TB spread?
Airborne
What are risk factors for TB?
Country and travel eg to India
Immunocompromised eg HIV
Homeless/crowded housing
IVDU
Smoking
Alcohol
Age
Are mycobacteria tuberculosis complexes (MTC) motile?
No, non-motile
Are mycobacteria tuberculosis complexes (MTC) spore forming?
No, non-spore forming
Are mycobacteria tuberculosis complexes (MTC) slow growing?
Yes, 15-20 hours
Are mycobacteria tuberculosis complexes (MTC) susceptible to phagolysosome killing?
No, they are resistant due to mycotic acid capsule
Mycobacteria tuberculosis complexes (MTC) are acid-____ bacteria that have a thick, waxy wall that is resistant to most staining methods.
acid-fast
What stain turns mycobacterium tuberculosis bright red?
Ziehl-Neelsen stain
The waxy cell wall of mycobacterium tuberculosis also makes it resistant to weak d_____
disinfectants
True or false: Mycobacterium tuberculosis needs oxygen to survive
True, strict aerobe
What happens when an alveolar macrophage engulfs m. tuberculosis?
Bacteria produces a protein preventing the lysosome fusing to the vesicle containing the bacteria, so it can’t break it down. Proliferates causing a localised infection = primary tuberculosis
What are symptoms of primary tuberculosis
Most asymptomatic
Some have flu-like symptoms
How long after initial infection of m tuberculosis for cell-mediated immunity to kick in?
around 3 weeks
What is the cell-mediated immune response to primary tuberculosis?
Immune cells surround TB infection, forming granuloma to wall off and prevent it spreading
What does caseous necrosis refer to in TB?
The tissue in the middle of the granuloma dying
caseous = cheese-like as dead tissue looks soft and white like cheese
What is the primary lesion in response to TB infection called?
Ghon focus (pulmonary caseating granuloma)
In upper parts of lung
Ghon ____ spreads to nearby lymph nodes, creating Ghon c_____
focus
complexes
Where do Ghon complexes normally occur?
Usually subpleural and occur in the lower lobes
What happens to the tissue encapsulated by the granuloma?
Undergoes fibrosis and often calcification producing scar tissue
What is a calcified Ghon complex called?
Ranke complex
Sometimes, the TB is killed of, leaving some scar tissue. In other cases, the TB is walled off but lies dormant. What factors may lead to the TB reactivating?
When the immune system is compromised eg AIDs or aging
Where does TB spread to after being reactivated?
One or both of the upper lobes of the lungs due to best oxygenation.
What happens when TB is reactivated and it spreads to the upper lobes?
Memory T cells recognise it and release cytokines
This causes more areas of caseous necrosis to form
The reactivation of TB and areas of caseous necrosis can form cavities, allowing the bacteria to spread through a____ and l_____ channels to other parts of the lungs
airways and lymphatic channels
What is TB in the airways called?
bronchopneumonia
What is it called when TB spreads through the vascular system to other parts of the body?
Systemic miliary TB
Where does TB commonly spread to in systemic miliary TB?
kidneys
Meninges
Lumbar vertebrae
Adrenal glands
Liver
Cervical lymph nodes
(K, My Love, A Lager, Cheers Love)
What does TB in the kidneys cause?
Sterile pyuria (WBCs in urine)
What does TB in meninges cause?
Meningitis
What does TB in the lumbar vertebrae cause?
Pott disease
(causes bone destruction, deformity and paraplegia)
what does TB in the adrenal glands cause?
Addison’s disease
What does TB in the liver cause?
Hepatitis
What does TB in the cervical lymph nodes cause?
Lymphadenitis in neck (scrofula)
What are symptoms of TB?
Characteristic night sweats and weight loss
Pyrexia (fever)
Chest pain
Patient looks unwell
Skin changes
Joint pain
How is TB diagnosed?
Mantoux skin test
Interferon gamma release assay (IGRA)
Sputum or bronchoalveolar lavage, and culture (positive will show bright red when stained with Ziehl Neelsen)
Chest XR
Biopsy
What is the Mantoux skin test?
Tuberculin (component of TB) is injected between layers of the dermis
T cells recognise tuberculin and produces small, localised reaction with 48-72 hours showing large area of induration
What does a positive Mantoux test mean?
Tee patient has been exposed to TB at some point
Interferon Gamma Release Assay (IGRA) is more s____ to TB than a Mantoux test and is unlikely to be positive from the BCG vaccine
specific
What happens after a positive sign of Mantoux or IGRA?
Chest XR to see whether TB is active
What mnemonic is used to describe how TB is treated?
RI2PE6
What does RI2PE6 stand for (treatment of TB)?
Rifampicin (2 months)
Isoniazid (2 months)
Pyramidine (6 months)
Ethanbutamol (6 months)
What is a side effect of Refampin?
Haematuria
What is a side effect of Isoniazid?
Peripheral neuropathy (tingling hands and feet)
What is a side effect of Pyrazinamide?
hepatitis
What is a side effect of Ethambutol?
Eye problems (optic neuritis)
True or false: adults with reactivated TB are most infectious
True
Adults with reactivated TB are typically kept in n_____ p_____ rooms with visitor wearing specific protective masks
negative pressure
