Tuberculosis Flashcards
definition of TB
contagious chronic bacterial infection caused by Mycobacterium tuberculosis
- primarily affect lungs , can affect any part of the body
How is Tb classified?
primary
post-primary
disseminated tuberculosis
What is primary tuberculosis
Primary infection stage
What is postprimary tuberculosis
–Reactivation TB
–Reinfection TB
–Secondary TB
What is Disseminated tuberculosis
–Extrapulmonary TB
–Miliary TB
–Tuberculosis-disseminated
How does primary tuberculosis manifest
- Begins when inhaled bacilli implant in the alveoli
- bacilli multiply over 3-4 wks initial response is inflammatory
- influx of leukocytes and macrophages move into the infected area to engulf-but not fully kill- the bacilli
- Pulm. capillaries dilate, interstitium fill with fluid and alveoli swell with edema, and then eventually consolidate
Clinically this phase coincides with a + tb skin test
pathology of primary tuberculosis
surrounds infected area produces a protective wall called tubercle or granuloma on X-ray small, sharply defined opacities
As it progresses the combination of the tubercles and lymph notes: Ghon complex
What is the fxn of tubercle
contain TB preventing further spread if the central core breaks down it fills with necrotic tissue AKA caseous lesion (B)
What is the ghon complex
primary pulmonary lesion where infection is encased
What is the Primary TB Symptoms
- if bacilli are isolated within the tubercles and immunity develops–> TB can be dormant for months/years
- Most are asymptomatic
- Only indication of TB is +skin test or blood test
what is the post-primary TB
the reactivation of TB months or years after initial infection
–> due to live tubercle bacilli remain dormant
–> TB can be reactivated with depressed immune systems or if individual have high risk factors
What if TB is uncontrolled
cavitation of granulomas develop& pt. progresses
–> lead to Cavitary Fibrocaseous
What is Cavitary Fibrocaseous TB?
- erosion into a bronchus
- cavity formed
- o2 tension favours growth of organism
What are the clinical manifestation of progressive pulmonary Tb?
- night sweats
- malaise
- anorexia &weight loss
- low grade fever, chills
- chest pain
- cough with purulent sputum with increasing frequency
- pulmonary hemorrhage as disease progresses – hemoptysis
- increasing dyspnea
What are other complication of TB
Gradual wasting of the body called consumption
–> pt is contagious at this stage
severe cases a deep turbercle can rupture and allow air and pus into the pleura
–>broncho-pleural fistula: pneumothorax
persistent cavity may be colonized by aspergillosis (fungus)
what is Disseminated/Miliary TB?
- Refers to the escape of tiny granulomas (pinhead size) from tubercle that travel to sites throughout the body by means of bloodstream & lymphatics
- can lead to necrotizing infection and organ damage, typically with ↑oxygen tension in other sits
what is the Anatomic Alterations of the Lungs
- Alveolar consolidation
- Alveolar-capillary destruction
- Caseous tubercles or granulomas
- Cavity formation
- Fibrosis and secondary calcification of the lung parenchyma
- Distortion and dilation of the bronchi
- Increased bronchial airway secretions
How is TB transmitted?
- Requires close, frequent and prolonged exposure to a source
- through inhalation of aerosols (airborne) –N95 mask fit tested
and these factors must be present:
–Viable bacilli in sputum or larynx of source
–Aerosolization of sputum by cough, bronchoscopy
–Adequate concentration of bacilli in air
–A susceptible host
–A sufficient length of time the host is breathing bicillary-laden air
What is the etiology
- caused by Mycobacterium tuberculosis
- Highly aerobic organisms
- non-motile, non-sporulating
- rod-shaped, acid-fast bacillus
- Resists staining, has a hard, waxy outer coat which protects against phagocytes, drugs
- slow growing aerobe - multiplies faster where there is high oxygen tension
e. g. Apex of lung, hilar regions
What is the Populations at Risk?
- close contacts with persons known to have TB (especially HCP), Public Health
- foreign-born
- medically unsupervised low-income, crowded populations (homeless shelters, LTC & correctional facilities
How to diagnosis for TB
- Mantoux tuberculin skin test
- Sputum Culture
- QuantiFERON®-TB Gold Test
What is the TB skint est guideline
Who
- a recently diagnosed individual with active TB
- Persons at ↑ risk of exposure
- people with impaired immunity
- healthcare workers susceptible to frequent exposure to TB
How i the mantoux test performed?
Mantoux skin test Injection of purified protein derivative (PPD) of TB
- subcutaneous/intradermal injection of M. tuberculosis on forearm
- Look for presence or absence of induration
**an induration of 10mm or greater is considered positive
this only tells if patient is exposed and infected with TB germ (not WHEN)
What is Tb skin test Interpretation
•Wheal less than 5 mm: negative
Wheal 5 mm to 9 mm: considered suspicious, retest req’d
Wheal 10 mm or greater: positive
- positive rxn is fairly sound evidence of recent or past infection or disease
- doesn’t confirm active TB
what is the false negatives TB interpretation
–Active TB persons –Poor technique –Recent viral infections - corticosteriods -metabolic disturbancecs –Age extremes
What is the false positives TB interpretation
–BCG vaccine
-Reaction to other non-tuberculousis mycobacterium
(M.avium, M kansasii)
What is the 2 step TB skin test include
- for high risk groups
- Helps rule out false negatives
- If +ve after the 1 st test, assess for active disease; start treatment
- If -ve, give the 2nd test in 1-4 wks
if there is positive rxn, it’s called the booster phenomenon, ie: exposed to TB in the past - this is not a new exposure
What is BCG
Bacille Calmette-Guerin
its a vaccine
characteristic of BCG
- live weakened bacterium M. Bovis
- TB skin test is always positive if vaccinated as adult
What is the contraindication for skin test
- blistering from past skin tests
- burns or eczema
- patients with clear presentation or Hx of TB, or previous Tx for TB
- major viral infection or recent live virus vaccination in past month
