Tuberculosis Flashcards
What organism causes tuberculosis?
Mycobacterium tuberculosis
Mycobacterium tuberculosis is a bacterium known for causing tuberculosis.
What unique component is found in the cell wall of Mycobacterium tuberculosis?
Mycolic acid
Mycolic acid contributes to the bacterium’s resistance to gram staining.
What type of staining is required for Mycobacterium tuberculosis?
Acid-fast stain
This staining method is necessary due to the unique cell wall composition.
What virulence factor does Mycobacterium tuberculosis produce?
Cord factor
Cord factor is a key factor that enhances the virulence of the bacterium.
What symptoms can tuberculosis present that are similar to lung cancer?
B symptoms, hemoptysis
B symptoms include fever, night sweats, and weight loss.
What living conditions or backgrounds are associated with an increased risk for tuberculosis?
Living in a homeless shelter or immigrant status from endemic area
Endemic areas include regions with high rates of tuberculosis, such as rural India and Albania.
What gross lung changes can tuberculosis cause?
Cavitations and calcification
These changes are observable during gross examination of the lungs.
What type of inflammation does tuberculosis cause on histological examination?
Caseating granulomatous inflammation
This type of inflammation is characteristic of tuberculosis infections.
What are Ghon foci/complexes?
Textbook descriptors for TB lesions
These terms refer to specific lung lesions associated with tuberculosis.
What complication can tuberculosis cause in the pericardium?
Constrictive pericarditis
This condition can also involve calcification.
What is miliary TB?
Disseminated TB affecting multiple organ systems
Miliary TB can lead to various serious complications.
List some complications of disseminated TB.
- Psoas abscess
- Pott disease
- Adrenal insufficiency
- Meningitis
- Osteomyelitis
- Arthritis
These complications can arise due to the spread of tuberculosis beyond the lungs.
What is the first step in the diagnosis of tuberculosis?
PPD test (type IV hypersensitivity)
The PPD test helps to identify if a person has been exposed to the tuberculosis bacterium.
What is the next best step if the PPD test is positive?
CXR
CXR stands for chest X-ray, which is used to check for active tuberculosis.
What should be done if the PPD test is positive but the CXR is negative?
Treat for latent TB or give TB prophylaxis
This involves administering isoniazid (INH) for 9 months along with vitamin B6.
What is the treatment for latent TB?
Isoniazid (INH) for 9 months + vitamin B6
Vitamin B6 is given to prevent neuropathy due to INH-related deficiency.
What is the next step if both the PPD and CXR tests are positive?
Treat for active TB
This treatment typically involves a regimen known as RIPE.
What does RIPE stand for in the treatment of active TB?
Rifampin, Isoniazid, Pyrazinamide, Ethambutol
This is the standard treatment course for active tuberculosis.
How long is the total treatment duration for active TB?
6 months
The treatment consists of 2 months of RIPE followed by 4 months of RI.
What is the nature of the BCG vaccine?
Live-attenuated
The BCG vaccine is used to provide some protection against tuberculosis.
How does a history of BCG vaccination change management based on PPD guidelines?
It does not
USMLE emphasizes that BCG vaccination does not alter PPD test interpretation.
How long after TB exposure will someone’s sputum cultures become positive?
2-5 weeks
This timeframe is critical for understanding the infectious period after exposure.
What is required for stimulation of alveolar macrophages to control TB?
interferon-g
Interferon-g is crucial for the immune response against tuberculosis.
What increased susceptibility to TB infections?
IFN-g deficiency or IL-12 receptor deficiency
IL-12 normally increases IFN-g levels.
What role does TNF-a play in relation to TB?
It is required to suppress TB
TNF-a is critical in controlling tuberculosis infections.
What drugs pose a risk of TB and should be avoided in silicosis patients?
infliximab, adalimumab, etanercept
These drugs can suppress the immune system, increasing susceptibility to TB.
What is considered a positive PPD test for individuals with a history of close contact to someone with active TB?
> 5mm
This threshold is used for high-risk individuals.
What is the PPD test positivity threshold for immunocompromised patients?
> 5mm
Includes AIDS patients and organ transplant recipients.
What is the PPD test positivity threshold for health care workers or prisoners?
> 10mm
This threshold applies to those in high-risk environments.
What is the PPD test positivity threshold for everyone else?
> 15mm
This is the general threshold for the broader population.
If a PPD test is positive, what should be done?
Never repeat it
Repeating a positive test can lead to unnecessary anxiety and confusion.
What must be done if a PPD test is negative?
It must be repeated in 1-2 weeks
This is to account for potential false-negatives.
