Tuberculosis Flashcards
Inhalation of M. tuberculosis has 1 of which 4 outcomes?
What % have which outcomes?
When does reactivation TB usually occur?
- Immediate clearance
- Rapid progression to active TB (primary disease)
- Reactivation of latent TB
- Latent infection (with or without subsequent reactivation)
90% clear/become latent
10% develop primary disease —> more common in immuosup
Reactivation TB usually occurs within 5 years
Which stains detect AFBs on microscopy?
Ziehl-Neelsen or Kinyoun stains
How long may it take to cultivate a positive M. tuberculosis culture and why?
May take 2-6 weeks
Due to VERY slow growth rate (generation time is 20-24 hours)
What % of people experience reactivation of latent TB?
And what RFs increase this chance?
5-15% of people with latent TB experience reactivation
Risk factors:
- Immunsup: HIV, transplant, TNF-alpha blockers
- Diseases: silicosis, dialysis
- Environment: close contacts
Common clinical features of primary tuberculosis?
Fever! (for weeks) Pleuritic chest pain Rarer sx: fatigue, cough, arthralgia, pharyngitis Night sweats Travel history/ contacts
Patients may also have disease at more distant sites –> cervical LNs, meningitis, pericarditis, miliary dissemination
Radiological findings in active pulmonary TB?
CXR and CT
CXR: hilar lymphadenopathy!!!/mediastinal lympadenopathy, pleural effusions, consolidation
Consolidation is usually either segmental or lobar & assoc. with ipsilateral hilar LN.
CXR changes may progress over time –> worsening appearances, cavitation
POSTPRIMARY/REACTIVATION TB USUALLY INVOVLES APICAL/POSTERIOR SEGMENTS OF UPPER LOBES >80%
CT: lymphadenopathy (commonly with caseous necrosis), usually dense & homogenous consolidation, cavities in 10%, effusions in 10%
Rarer: large masses, PTx
Common clinical features of reactivation TB
Usually insidious…
Fever Night sweats Fatigue Weight loss Dyspnoea Cough --> worsens as disease progresses (may develop haemoptysis)
Advanced disease… pleuritic chest pain/ dyspnoea with extensive parenchymal involvement, painful ulcers of mouth/GI tract due to swallowing secretions, anorexia/wasting/malaise
Tuberculomas (in lungs)
Exam usually normal unless advanced
Pulmonary complications of TB
Haemoptysis Extensive pulmonary destruction PTx Bronchiectasis Fistulas Tracheobronchial stenosis Malignancy Chronic aspergillosis Respiratory failure Septic shock
All more common after reactivation TB disease
Common ddx to consider for a patient presenting with TB symptoms
- Other mycobacterium pneumonia
- Lymphoma/malignancy
- Fungal infection
- Lung abscess
- Septic emboli
- Meiloidosis (burkholderia - similar sx and imaging findings)
Why test people for latent TB?
A. People at risk of new infection - HCWs, homeless shelters, other high endemic areas, close contacts
B. Risk of progression from latent to active because of comorbidities
Diagnosis of active TB?
History + radiology
PLUS (options):
- Isolate M TB from bodily secretion (sputum MCS - takes up to 6 weeks, BAL, pleural fluid, tissue/lung biopsy)
- Sputum AFB smears (3 x consecutive mornings)
- Nucleic acid amplification testing (NAA) of sputum - positive NAA with or without sputum AFB is considered sufficient for TB diagnosis (should be back within a few days)… AKA TB PCR!
…. From reading it seems that more weight is given to the NAA result than the AFB smears
REPORT to public health authority
What if you can’t get sputum for AFB smears, NAA and MCS?
- Try hypertonic saline + chest physio
- Bronchoscopy - with BAL and tissue sample
Requirements before starting TB treatment?
- Patient weight
- FBE, LFTs, UECs
- Visual acuity & colour vision
- HIV testing, HBV/HCV testing
- Discuss contraception (COCP interaction)
When is a patient presumed non infectious from TB?
Around 2 weeks of daily rx with standard short course therapy…
LONGER if: Extensive cavitations Suspected drug resistant TB Smear positive Who do not improve with therapy
Note that children <10 considered non infectious & extrapulmonary TB in the absence of lung disease is NOT infectious
What is drug resistant TB? Types and commonness
Standard rx not appropriate
Isoniazid-monoresistant TB in 10% of cases in Australia
Multidrug resistant RB (at least isoniazid & rifampicin) uncommon in Australia)
