Tuberculosis Flashcards
What organism causes tuberculosis?
Mycobacterium tuberculosis (vast majority in U.S.)
M. tuberculosis organisms are also called tubercle bacilli
Other myobacteria that can cause tuberculous disease include: M. bovis M. africanum M. microti M. Canetti
What is a common type of Mycobacteria that does not cause TB?
M. avium
Mycobacteria that do not cause TB are often called nontuberculous mycobacteria. Nontuberculous mycobacteria are NOT usually spread from person to person
Where does TB disease usually occur?
in the lungs (pulmonary TB), but can also occur in other places in the body (extrapulmonary TB)
What is disseminated TB
When tubercle bacilli enter the bloodstream and are carried to all parts of the body, where they grow and cause disease in multiple sites
LTBI
Latent TB Infection:
When someone is infected with TB and their immune system keeps the bacilli under control, it is referred to as LTBI. People with LTBI do not have symptoms of TB, and they cannot spread TB to others
TB Disease
In some people with LTBI, the immune system cannot keep the tubercle bacilli under control and the bacilli begin to multiply rapidly, resulting in TB disease (AKA Active Disease). People with TB disease can spread TB to others
When can TB Disease occur?
Very soon after infection or many years after infection
Risk factors for LTBI
About 10% of people with LTBI will develop TB disease at some point, but the greatest risk is in the first year or two after infection. Certain medical conditions also put some people at higher risk
Risk factors for people infected with both M. Tuberculosis and HIV
With people infected with both, risk of developing TB disease is about 7 to 10 % per year.
For people only infected with M. tuberculosis, the risk of developing TB disease is 10% over a lifetime
State of Bacilli - LTBI vs TB Disease (pulmonary)
LTBI - inactive tubercle bacilli in the body
TB Disease - Active tubercle bacilli in the body
Test Results - LTBI vs TB Disease (pulmonary)
Tuberculin skin tests or interferon-gamma release assay tests results usually positive for both
Chest X-ray results - LTBI vs TB Disease (pulmonary)
LTBI - Chest x-ray usually normal
TB Disease - Chest x-ray usually abnormal
Sputum Smears and Cultures Results - - LTBI vs TB Disease (pulmonary)
LTBI - Sputum smears and cultures negative
TB Disease - Sputum smears and cultures may be positive
Symptoms - LTBI vs TB Disease (pulmonary)
LTBI - No symptoms
TB Disease - Symptoms such as cough, fever, weight loss
Infectiousness - LTBI vs TB Disease (pulmonary)
LTBI - Not infectious
TB Disease - Often infectious before treatment
Diagnosis - LTBI vs TB Disease (pulmonary)
LTBI - Not a case of TB
TB Disease - A case of TB
Symptoms of TB Disease
Most people will have symptoms:
TB (Pulmonary)
- Cough lasting 3 weeks or more
- Pain in the chest when breathing or coughing
- Coughing up sputum or blood
General symptoms of TB disease (pulmonary or extrapulmonary):
- Weight Loss
- Loss of appetite
- Fatigue
- Malaise
- Fever
- Night Sweats
Other symptoms depend on the part of the body that is affected by the disease.
Drug-resistant TB
Drug-resistant TB is caused by M. tuberculosis organisms that are resistant to at least one of the first line TB treatment drugs
What are the first-line TB treatment drugs
- isoniazid
- rifampin
- pyrazinamide
- ethambutol
Primary resistance
When drug-resistant TB can be transmitted person to person
Secondary resistance
Develops during TB treatment, either because patient was not treated with appropriate regimen or patient did not follow the treatment regimen as prescribed.
What are the two best first line TB treatment drugs
- isoniazid
- rifampin
XDR TB
Extensively drug-resistant TB
Occurs if the tubercle bacilli are resistant to isoniazid and rifampin, plus resistant to any fluoroquinolone (e.g. levofloxacin and moxifloxacin) and at least one of three injectable second-line drugs (e.g. amikacin, kanamycin, or capreomycin).
What are the three injectable second line drugs for TB
- amikacin
- kanamycin
- capreomycin
MDR TB
Multidrug-resistant TB
If tubercle bacilli are resistant to at least isoniazid and rifampin
Poly-resistant TB
Resistant to at least two TB drugs, but not both isoniazid and rifampin