Lecture 17 - TB And Chronic Resp Infection

Question 1

TB diagnostic investigation

Answer 1

• 3 spontaneous sputum samples collected
• sputum smear is positive for acid fast bacilli
• sputum is sent for culture: positive after 8 ays for M. Tb
• durg susceptibility testing performed showeing the organism if scusceptible to first line TB med

Question 2

In Australia now, how many people of affected people die of TB

Answer 2

• 3% of people, when treatment fail

Question 3

Global and australian TB burden

Answer 3

• TB remains leading infectious cause of death globally
• 9.6 million new cases and 1.5 million deaths
• 0.4 million deaths among people living with HIV
• 58% of all TB occurs in asia-pacific
• Australia has 1.200-1.400 cases of TB each year

Question 4

Biology of MB.TB

Answer 4

• Mycobacteria are aerobic, non-motile bacteria that stain positive with acif fast alcohol stain
• lipid-rich hydrophobic cell wall, thicher than most other bacteria
• cell wall is impermeable to antibiotics and disinfectants
• this allows the pathogen to evade the human immune system

Question 5

Macroscopic pulmonary TB

Answer 5

• caseous granuloma - big cavities due to inflammation over time
• apices of lung most affected by TB because a lot more ventilation compared to perfusion

Question 6

Immunological response of TB

Answer 6

• after bacteria enters lung, TB is phagocytosed by AM and taken up by neutrophils and dendritic cells
• innate and adaptive immune factors play an important role
• a variety of host cell types are required to contain the bacteria
• Immunological impairment reduces the capacity to prevent disease

Question 7

Testing for latent TB infection: Mantoux Test

Answer 7

• TST indicates the person has been exposed to antigens in M TB
• can have false positive results from BCG vaccination or other non-Tb mycobacteria
• use a ball point pen to read it

Question 8

Interferon gamma release assay (IGRA)

Answer 8

• newer assay that use more specific MTB antigen
• looks for ESAT-6 and CFP-10
• absent from BCG and most non-TB mycobacteria
• measures IFN-g release by antigens using enzyme-linked immunoassay
• quive a quantitative outcome
• neither TST or IGRA are specific predictors of subsequent progression to TB

Question 9

Latent TB vs TB disease

Answer 9

• both caused by MB
• both have TST positive
• CXR: normal vs abnormal
• Sputum smear and culture: Negative vs positive
• No symptoms vs symptoms
• not infection vs infectious

Question 10

Clinical presentation of TB

Answer 10

• migrant background
• pulmonary TB comprises 70% of TB: prolonged cough with sputum, haemoptysis, low grade fevers and night sweats, weight loss
• Extrapulmonary TB - lymph nodes, dypnoea, abdominal pain, haematuria, GI symptoms, bone pain

Question 11

Risk factors for developing TB

Answer 11

• environmental
• host-related factors: immunological impairment, underlying disease, medication
• bacterial factors

Question 12

Diagnostic approach to TB

Answer 12

• confirmation of diagnois
• sputum collection (morning ones are most sensitive)
• sputum smear and culture
• nucleic acid amplification test
• bronchoscopy if sputum samples are non-diagnostis
• tissye biopsy

Question 13

Management of TB goal

Answer 13

• eradicate infection with MB TB
• prevent development of drug resistance
• prevent relapse

Question 14

Management guidelines

Answer 14

• at least 3 drugs to which the bacteria is susceptible, for a minimum of 6 months
• TB is a notifiable disease

Question 15

Standard TB regimen

Answer 15

• 2 months of : Isoniazid, Rifampicin, Pyrazinamide, Ethambutol
• 4 months of isoniazid and Rifampicin

Question 16

TB contact tracing

Answer 16

• TST or IGRA

- exclude active disease with chest XRAY

Question 17

Treatment of latent TB

Answer 17

• single antibiotic for 6-12 months

- treatment with isoniazid reduces risk of progressing to TB by 60-90% in infected contacts of drug susceptible TB

Question 18

Causes of bronchiectasis

Answer 18

• abnormal widening of the bronchi and their branches resulting in an increase risk of infection
• congenital causes: CF, primary ciliary dysfunction, a-1 antitrypsin deficiency
• acquired causes: infections, foreign body, TB, aspiration, rheumatic disorders, non-tb mb

Question 19

Clinical features of bronchiectasis

Answer 19

• cough and daily production of mucopurulent sputum lasting from months to years
• dyspnoea, wheeze, chest pain

Question 20

Common bacteria occuring in bronchiectasis

Answer 20

• H.influenza, Moraxella catarrhalis, staph, aureus, pseudomonas, aeroginosa, strep pneumonia
• atypical organisms: nont tb mb, aspergillus

Question 21

NTM in bronchiectasis

Answer 21

• NTM are one of several chronic infections that can occur in bronchiectasis
• NTM are ubiquitous in the envt
• associated with biofilm formation
• hydrophobic nature results in preferential aerosolozation from water
• many resist high temp and low pH

Question 22

Diagnostic investigation of bronchiectasis

Answer 22

• blood test for ingection
• test for CF: CFTR
• Sputum
• chest imaging: HRCT is used to define bronchiectasis
• pulmonary function test: obstructive pattern
• consider additional tests

Question 23

Management of bronchiectasis

Answer 23

• antibiotics for 10-14 days
• airway clearance

Prevent exacerbations

• antibiotics: long term macrolyde
• airway hydration, airway clearance techniques
• immunization against influenza and pneumococcus
• pulmonary rehab
• surgery