Tuberculosis Flashcards
Mycobacterium tuberculosis:
doesn’t gram stain
-culture takes 2-3 weeks
TB info:
1/3 of world pop. is infected
*** leading cause of death in HIV pts
TB risk factors:
Close contacts of persons known or suspected to have active TB
Foreign-born persons from areas where TB is common
Populations with increased incidence of latent M. tuberculosis infection or TB disease, such as homeless, IVDA, HIV patients
Residents or health care workers (HCWs) exposed to high-risk patients (hospitals, homeless shelters, prisons, nursing homes, etc)
Children < 5yo with positive TB test
People who are immunocompromised (HIV, substance abuse, diabetes, silicosis, severe kidney disease, low body weight, organ transplant recipients, head/neck cancer patients, steroid treatment, RA or Crohn’s
TB transmission:
- spread via airborne droplet nuclei
- 1-3 bacilli per droplet
- remains in air for hours
TB pathogenesis:
- droplet inhaled and travels to alveoli where it multiplies
- some enter bloodstream and travel to other areas such as brain
- normally contained within 2-8 weeks by body. if not it spreads
Latent TB infection (LTBI)
- can stay latent or can breakdown and produce TB disease
- Latent detected via TST or interferon-gamma release assay
- LTBI pts are not infectious
Active TB:
- 10% of patients
- can occur soon after infections or years later
- can spread disease
- positive cultures confirm diagnosis
- reactivation occurs within 2 years in 50% of infected pts.
Most common site of TB:
- Lungs (usually infectious)
- Apices most common site of reactivation
- Caseating granulomas
Miliary TB:
Bacilli can spread to all parts of body, and fatal if untreated
-Millet seed appearance on CXR
CNS TB:
-usually occurs as meningitis, but can occur in brain or spine
GHON complex
- radiodense area on CXR
- stable granuloma
- found in 20% of LTBI
extra pulmonary TB:
usually not infectious, unless person has
Concomitant pulmonary disease,
Extrapulmonary disease in the oral cavity or larynx, or
Extrapulmonary disease with open site, especially with aerosolized fluid.
who should be tested:
Contacts of persons known or suspected to have infectious TB disease
People who have come to the United States within the last 5 years from areas of the world where TB is common (ex: Asia, Africa, Eastern Europe, Latin America, and Russia)
Persons who visit areas of the world where TB is common
People who live or work in congregate settings whose clients are at increased risk for TB disease
Health care workers who serve clients who are at increased risk for TB disease
Populations defined as high risk for LTBI or active TB disease, such as medically underserved, low-income persons, or persons who abuse drugs or alcohol
Infants, children, and adolescents exposed to adults at increased risk for infection or disease
testing methods for TB infection in US:
Mantoux tuberculin skin test (TST)
Interferon Gamma Release Assays (IGRAs):
QuantiFERON-TB Gold In-Tube (QFT-GIT)®, and
T-Spot.TB®
administering TST:
Inject 0.1 ml of PPD (5 tuberculin units) into forearm at 5 – 15 degree angle between skin layers Produce wheal (raised area) 6–10 mm in diameter Follow universal precautions for infection control
Reading TST:
Trained health care worker assesses reaction 48–72 hours after injection
Palpate injection site to find raised area
Measure diameter of induration across forearm; only measure induration, not redness
Record size of induration in millimeters; record “0” if no induration found
≥5 mm induration is classified as positive in
HIV-infected persons
Recent contacts of infectious TB
Persons with fibrotic changes on chest radiograph consistent with prior TB
Patients with organ transplants and other immunosuppressed patients
≥10 mm induration is classified as positive in
Recent arrivals from high-prevalence countries
Injection drug users
Residents and employees of high-risk congregate settings
Mycobacteriology laboratory personnel
Persons with conditions that increase risk for progressing to TB
Children <5 years of age, or children and youth exposed to adults at high risk
≥15 mm is classified as positive in
Persons with no known risk factors for TB
Interferon Gamma Release Assays (IGRAs)
IGRAs detect M. tb infection by measuring immune response in blood
Cannot differentiate between TB and LTBI
other tests needed
May be used for surveillance/screening, or to find those who will benefit from treatment
FDA-approved IGRAs are QFT Gold In-Tube and T- Spot.TB test
Evaluation of Persons with Positive TB Tests
Facilities should consult with local health department before starting testing program to ensure evaluation and treatment resources are available
Persons with positive test should be evaluated for disease
If disease is ruled out, consider for LTBI treatment
If patient not willing or able to take treatment, educate on TB signs and symptoms
BCG Vaccination:
Vaccine made from live, attenuated (weakened) strain of M. bovis
Early version first given to humans in 1921
Many TB-prevalent countries vaccinate infants to prevent severe TB disease
BCG not generally recommended in the U.S.
Use BCG only after consultation with local health department and TB experts
Interpretation of TB Test Results in BCG-Vaccinated Persons
TST or IGRA not contraindicated for BCG-vaccinated persons
Results used to support or exclude diagnosis of infection
In BCG-vaccinated, interpret TST with same criteria used for non BCG vaccinated
Who should be evaluated for TB?
Cough lasting more than 3 weeks
Unexplained wt loss
Hemoptysis
Additional symptoms: fever, chills, night sweats
Medical Evaluation for TB
Medical history Physical examination Test for TB infection Chest radiograph Bacteriologic examination
Medical Hx:
Symptoms of disease; how long
History of TB exposure, infection, or disease
Past TB treatment
Demographic risk factors for TB
Medical conditions that increase risk for TB disease
Symptoms of pulmonary TB:
Prolonged productive cough (3 weeks or longer) Hemoptysis Loss of appetite Unexplained weight loss Night sweats, fever Fatigue Chest pain
Symptoms of possible extrapulmonary TB:
Blood in the urine (TB of the kidney) Headache/confusion (TB meningitis) Back pain (TB of the spine) Hoarseness (TB of the larynx) Loss of appetite, unexplained weight loss Night sweats, fever Fatigue
Physical Examination of TB:
Provides valuable information about the patient’s overall condition
Cannot be used to confirm or rule out TB disease
May have dullness to percussion, rales, increased vocal fremitus
CBC with TB:
elevated WBC
CXR with TB:
Chest abnormalities suggest, but do not confirm, TB disease
Posterior-anterior view is standard
Apical/posterior areas of upper lobe or superior areas of lower lobe often show patchy or nodular infiltrates
May see cavitation with air-fluid levels as infection progresses
In immunosuppressed (e.g., HIV infected), lesions may have atypical appearance
Less likely to have + TST or fever
HIV pts pulmonary TB may have atypical radiograph:
Less common: cavitary disease (with higher CD4 counts)
More common: infiltrates, adenopathy, or normal radiograph (with lower CD4 counts)
With signs/symptoms, negative radiograph does not rule out disease
With no signs/symptoms and positive TB test, negative radiograph may rule out TB in HIV-negative person
Testing/ specimens:
Specimen collection AFB smear classification NAA testing Culture and identification Drug-susceptibility testing
Specimen collection, processing, and review
All persons suspected of TB disease should have sputum cultured
Collect at least 3 sputum specimens at 8- to 24-hour intervals, at least 1 in the morning
Follow infection control precautions during specimen collection
Collection methods include coughing, sputum induction, bronchoscopy, gastric aspiration
First evidence of mycobacteria in testing come from:
detecting AFB in smears
- results in 24
- provides preliminary presumptive diagnosis of TB
Nucleic Acid Amiplification testing in TB:
NAA tests rapidly identify a specimen via DNA and RNA amplification
Benefits may include
Earlier lab confirmation of TB disease
Earlier respiratory isolation and treatment initiation
Improved patient outcomes; interruption of transmission
Perform at least 1 NAA test on each pulmonary TB suspect
A single negative NAA test does not exclude TB
*Gold Standard for confirming TB:
Culture
- culture all specimens even if smear or NAA is negative
- 4-14 days
- culture monthly until 2 consecutive negative cultures
Drug-susceptibility testing:
Conduct drug-susceptibility testing on initial M. tb isolate
Promptly forward results to the health department
Repeat for patients who
Do not respond to therapy or
Have positive cultures despite 3 months of therapy
New TB test: XPERT MTB/RIF Assay:
Test detects M. tb complex and rifampin resistance simultaneously
Results in 2 hrs
Sputum sample
TB 1st Line drugs:
Isoniazid Rifampin Pyrazinamide Ethambutol Rifabutin* Rifapentine
- = Not approved by the U.S. Food and Drug Administration for use in the treatment of TB
Second line TB drugs:
Streptomycin Cycloserine p-Aminosalicylic acid Ethionamide Amikacin or kanamycin* Capreomycin Levofloxacin* Moxifloxacin* Gatifloxacin*
*= Not approved by the U.S. Food and Drug Administration for use in the treatment of TB
RIPE=
Rifampin/rifapentine
Isoniazid
Pyrazinamide
Ethambutol
