Resp L6.2 Flashcards
1) How does Tb occur?
2) What can make a patient more contagious ?
1)- Results from inhalation of droplet nuclei containing M. Tb
(coughing etc)
-Ingestion of M.tb by alveolar macrophages
-replication of bacilli inside macrophages (triggers: inflammatory response, activation of t helper 1 cells)
2) PATIENTS WITH PULMONARY CAVITY LESIONS MORE CONTAGIOUS DUE TO LARGE NO OF BACTERIA WITHIN LESIONS
What is the bacteria which causes Tb (pulmonary tubercuolosis)?
What are common symptoms?
1) Mycobacterium tubercuolosis (M. Tb)
2) Cough, Chest Pain, Fever, Anorexia, Night sweapts, Haemoptysis
3) What is the differnce between Latent Tb and Active Tb?
4) What 2 factors can cause active Tb instead of latent Tb?
Latent - granuloma formation. (M. Tb surrounded with marcophages forming granuloma/tubercle). Graunuloma acts as containment strategy. Keeps M. tb bacteri dormant preventing spread. Latent Tb - no symptoms (carry bacteria in inactive form)
Active Tb - Immune system failure -immunse system cannto contain M. tb in granulomas. Bacteria multiply, symptoms (cough, chest pain, fever, )
Contagious, spread to others.
4) Failed immune system activation (IMPAIRED CELLULAR IMMMUNITY)and
Immunosuppresion
What is primary progressive Tb?
What can cause impared cellular immunity?
Weakened immune system
Increases risk of reactivating latent Tb
-HIV infection
-Immunosuppression
-Organ transplantation
Reason for reactivation: TB reactivation is a type IV delayed hypersensitivity reaction, mediated by T cells. When T cells compromised, they cannot control bacteria.
Reactivation leads to Granulomatous necrosis (caseous histological apperance)
Describe the formation of a granuloma
-granuloma
-tubercle
-ghon focus
-ghon complex
-ranke complex
Go through the progression of Tb
(Primary, secondary, millary)
- Primary:
-initial infection with M. Tb
-may progress to active disease
CAN BE SEEN AT LOWER, MID LOBES OF LUNGS - Secondary Tb (reactivation Tb)
-Primary Tb infection heals, latent Tb
-If immune system weakens later, latent Tb reactivates, causing secondary Tb
CAN BE SEEN UPPER LOBES OF LUNGS - Millary Tb: WIDESPREAD DISSEMINATION OF BACTERIA THROUGH BLOODSTREAM
-Rare
-Tb bacteria spread from lungs to other parts of body through blood.
-M Tb distrovuted to other organs (spleen, liver, BRAIN(meninges))
-Children higher risk
How do we diagnose active Tb?
Diagram for Tb testing
What groups of people can chest X-Ray finding look different in for Tb patients?
Upper lobe infiltrates(abnormal areas in upper parts of lung) seen on X-ray - typical sign in Tb patients
-Children
-People with weakened immune systems (such as those who are immunocompromised, have HIV, or have diabetes)
Chest X-Ray of patient with Tb
Ranke complex - sign of healed primary Tb. Later stafe of Ghon complex, which develops during primary Tb infection
The calcification of both the Ghon lesion and the lymph nodes indicates that the TB infection has been controlled and is no longer active. It shows that the immune system successfully walled off the bacteria and that the tissue is healing or has healed.
Radiological Significance:
The calcified areas can be seen on a chest X-ray (CXR) and typically indicate that the person had a prior TB infection that is now inactive or latent.
Chest X-Ray of patient with Tb
image on the left demonstrates bilateral consolidation in the lower zones, while the image on the right shows miliary tuberculosis, described as widespread, randomly distributed, innumerable tiny nodules in both lungs without consolidation.
BILATERAL CONSOLIDATION
-consolidation: filling of lung air spaces with fluid, pus, blood cells, lungs appear whiter (denser) on X-ray. Bilateral lower zone consolidation seen in conditions including
-Pneumonia
-pumonary edema
1) How does Miliary Tb occur?
2) State symptoms of Miliary Tb
3) Miliary TB CXR
1) - M. tb gains entry to blood stream
- Widespread dissemination throughout body
-Multiple foci of infection in different organs
-High fatality rate
-Most common in young children with HIV (immunocompromised patients)
2) - Fever unknown origin
-Weakness
-Malaise
1) What is the AFB smear in Tb?
Sputum Acid-Fast Bacilli (AFB) Smear in Tuberculosis (TB)
Test looks for AFB in sputum samples. Consistent with M. Tb
How it works:
-Sputum sample stained with special dye
-AFB retain dye even after exposore to acidic media, characteristic of Tb bacteria
Results
If sputum is positive for AFB, the
results will be graded from 1+ to
3+ or 4+ depending on number
of organisms seen and grading
scale. Smear positivity and its
grading may help estimate the
degree of infectiousness and
burden of TB
Around 40% to 50% of cases are AFB smear negative
What is a sputum culture?
Most sensitive, specific test
Should always be performed
used to:
Confirm the presence of Mycobacterium tuberculosis (M. tb). Perform drug susceptibility testing (DST) to guide appropriate treatment, especially in cases of drug-resistant TB.
Growth on solid media may take 4 to 8
weeks; growth in liquid media may be
detected in 1 to 3 weeks. Growth on
solid media if positive is reported on
quantitation scale (1+ to 4+).
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Investigations to order (Active TB)
15% to 20% have negative cultures
How to investigate for Active TB?
Do we always see abnormal chest X-Ray in
TB?
Extrapulmonary TB
Other investigations
Tuberculosis testing - Latent TB
Mantoux test- TST
Mantoux test- TST
LATENT TB Test Interpretation
The Mantoux tuberculin skin
test (TST) is one method of
determining whether a person is
infected with M. tb
The test is performed by
injecting 0.1 mL of tuberculin
purified protein derivative into
the inner surface of the forearm
The skin test reaction should be
read between 48- 82 hours after
administration
How do we manage Latent TB?
What is contact tracing?
What are the three steps?
What is Multidrug-Resistant TB (MDR-TB)?
How is it caused?
caused by Mycobacterium tuberculosis strains that are resistant to at least two of the most powerful first-line TB drugs:
Isoniazid (INH) Rifampin (RIF)
Incomplete Treatment:
Poor Quality Drugs:
Lack of Availability:
Incorrect Dosage or Duration:
Differential diagnosis of TB
