IOD-TB

Question 1

MT?

Answer 1

mycobacterum tuberculosis-small bacillus rod and lipid rich walls
slow growing and have latency
Has efficiently established latent infection has enabled it to spread to nearly one-third of individuals worldwide.

Question 2

pathology?

Answer 2

spread by resp route
terminal air spaces at periphery of lungs underneath pleural surface
bacilli engulfed by alveolar macrophages but cannot be destroyed so it multiplies and releases more
spreads into blood and kidneys, spleen, adrenals bones and meninges

Question 3

how many people are asymptomatic?

Answer 3

95%

Question 4

T cell immunity?

Answer 4

macropahges activate CD4+ T helper cells via MHCII
Th1 make IFNg activating macrophages and aggregate to form granulomas these wall off viable organisms in anoxic and acidic environments to kill bacteria
caseous necrosis and seals off by fibrous scar tissue that can calcify
giant cells form as many macrophages fuse to contain the metabolically active bacteria

Question 5

Signs?

Answer 5

calcified scar in lung parenchyma and hilar LN-ghon complex

Question 6

Active TB?

Answer 6

result of initial infection

reactivation of latent disease

Question 7

rf for active?

Answer 7

immunocompromised

immigration, elderly, alcoholics, DM

Question 8

patho of active?

Answer 8

Th2-inappropriate amount of immune cells are recruited-intense but ineffective immune response-damage

Question 9

pulmonary?

Answer 9

chronic
unwell, persistent cough and constitutional symptoms
airway erosion-necrotic material drained sso cavity forms with organisms-spread when cough

Question 10

diagnosis of active?

Answer 10

history
CT/CXR-
labs-
3 cough/sputum samples-via cough or saline/nebuliser or endoscopy
slide-for acid and alcohol fast bacilli
first line-auramine-fluorescent or NAAT-specific and quick
gold standard-Ziehl-neelsen stain-3-6 wks

Question 11

extrapulmonary?

Answer 11

15%
haematogenous dissemination of bacilli to many organs
walled off into small granulomas where mycobacteria remain dormant and reactivate later
LN and kidneys
miliary Tb-wide dissemination

Question 12

steps in extrapulmonary?

Answer 12

2 months-rifampicin, isoniazid, pyrazinamide, ethambutol
4 months- Isoniazid and Rifampicin
If there is central nervous system involvement the continuation phase of treatment is extended to 10 months making a 12 month full treatment plan.

TB treatment is taken all together on an empty stomach 1 hour before breakfast; compliance is essential for cure.

notified
contact tracing

Question 13

Natural history?

Answer 13

primary infection
immune clearance
establishment of latent infection
reactivation of TB causing disease
infectious TB spread by coughing

Question 14

outcomes?

Answer 14

eradicated into calcified form
1 in 10 reactivate to form abcessses travelling into airways and blood
deposit where blood flow changes-BBB and lumbar spine

Question 15

signs?

Answer 15

Cough (2-3 weeks or longer)
Fevers
Unexplained weight loss
Drenching night sweats
Lymphadenopathy

Question 16

Epidemiology?

Answer 16

history of prior TB infection or disease,
known or possible TB exposure,
and/or past or present residence in or travel to an area where TB is endemic).
immunocompromised?

Question 17

CXR findings

Answer 17

pulmonary-upper lobe consolidation-larger airways and cavities
miliary (blood)-small nodules across lung fields
Tree and leaf sign on CT

Question 18

cultures?

Answer 18

Conventional culture can detect as few as 10 bacteria/mL
the sensitivity and specificity of sputum culture are about 80 and 98 % respectively
Culture is required for drug susceptibility testing and for species identification.
Culture is on solid media (Lowenstein-Jensen) or liquid culture (Middlebrook)

Question 19

NAA info?

Answer 19

Xpert MTB/RIF assay / Xpert MTB/RIF Ultra assay
landmark development in TB diagnostics

One Xpert MTB/RIF test on sputum detects 90% of pulmonary TB
99% of smear-positive disease
75% of smear-negative disease

High sensitivity of Xpert MTB/RIF for rifampicin resistance –rpoB mutations

Confirmatory drug sensitivity testing is needed

Question 20

Urine test?

Answer 20

Urine-based detection of mycobacterial cell wall glycolipid lipoarabinomannan (urine LAM)
point-of-care assay for diagnosis of TB.
Cheap and quick
Value in HIV positive patients with low CD4 count

Question 21

link to HIV?

Answer 21

Depletion of CD4 cells leads to reactivation of latent TB infeciton and impairs containment of active infection making disseminatin and extrapulmonary disease more likely.
TB increases the transcriptional activity of HIV and accelerates and promotes its progress driving futher immune supression.

Question 22

what does co-infection lead to?

Answer 22

depletion of M tuberculosis-specific CD4 T lymphocytes and type-1 cytokine production

dysfunction of the CD4 T lymphocyte–macrophage immune axis

impairs the host’s ability to form granulomas.
Usually when CD4 cells are below 1000 but above 500

Question 23

GOV aims?

Answer 23

decrease incidence
increase vaccinations and tracing
reduces resistant TB

Question 24

Epidemiology facts?

Answer 24

High in Africa, East Asia and UK
High notifications in UK
Rates decreasing with vaccine
linked to SE status, prison IV drug use, homelessness-1.5x to die from it
UK born individuals get TB in the UK
Romania has highest rate of drug-resistant TB

Question 25

DOT?

Answer 25

Directly observed treatment is known as DOT.
Each DOT case is assessed by the TB specialist team regarding the patient’s ability to adhere to the six-month treatment regimen.
DOT is initiated for those at risk of being unable to adhere to treatment.
A professional case worker, person trained to be a DOT observer, or a trusted family member or friend will watch the patient take their TB treatment.
Primary care providers, such as GP practices
or pharmacists, may be asked to provide DOT.

Question 26

contact

tracing?

Answer 26

TB nurses
close contacts-CXR, Symptom list, BCG/mantoux, G interferon assay test-immune memory of human TB
1% of contacts screened have active TB
10% of contacts screened have latent TB infection
60% of child contacts under 2 years will go onto develop active TB.