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TB Flashcards

1
Q

How is TB transmitted?

A

Inhalation of droplet nuclei containing M.tuberculosis

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2
Q

What is a ghon complex?

A

Primary TB lesion with regional lymph involvement

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3
Q

What is ghon focus?

A

Granuloma caused by TB

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4
Q

What are the possibilities progression of TB primary infection?

A

Local progression –> disseminated disease –> miliary TB

Latent –> reactivation 10%

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5
Q

List risk factors for active TB disease? (6)

A

Diabetes
Alcohol
Malnutrition
CKD requiring dialysis
Smoking
TNF A inhibitors

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6
Q

Define Latent TB

A

State of persistent immune response to stimulation by M.tub antigens with no clinically manifest active TB

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7
Q

What is the test for latent TB?

A

IGRA/Quantiferon gold
TST Mantoux test

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8
Q

What are causes of false positive TST?

A

Previous TB vaccination with the bacille Calmette-Guérin (BCG) vaccine

Infection with nontuberculosis mycobacteria (mycobacteria other than M. tuberculosis)

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9
Q

Classical symptoms of pulmonary TB

A

Cough +/- haemoptysis (suggestive of cavities)
Fever
Night sweats

85% of all TB is pulmonary - cough duration usually longer than 2 weeks

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10
Q

Differential for cavitiating disease

A

Staph
Klebsiella
TB
Nocardia
Actinomyeisis
Cryptococcus neoformans
Histoplasmosis
Blastomyocisis
Paracoccidymyosis
Paragnomis
Squamous cell carcnimoa
Polyangitis Granulomatous

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11
Q

Define miliary TB

A

Massive lymphohaematogenous dissemination of M.tuberculosis

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12
Q

What is the CSF features in TB?

A

Straw coloured exudates
Elevated LDH
Elevated protein
Lymphocyte predominance
Can have low glucose

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13
Q

What is the second commonest TB?

A

Lymph node aka Cold abscess

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14
Q

Pathophysiology of CNS TB/explain the clinical presenation (3 points)

A

Classically basal meninges affected - inflammatory exudates in the basal cisterns obstruct CSF flow and cause hydrocephalus

Localised necrotising granulomatous inflammation can get tuberculomas.

Vasculitiis can cause MCA stroke syndrome/basal ganglia and internal capsule infaarcts

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15
Q

What are the 3 stages of TB meningitis?

A

Stage 1 - prodromal phase no definite neurologic symptoms

Stage 2 - meningeal irritation with slight /no neurological defecit

Stage 3 - severe cognitive defect, convulsions, focal neurological defecit

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16
Q

What is the role of steroids in TB meningitis?

A

Give dexamethasone should be given for all patients with TBM regardless of disease severity - emerging evidence no role in HIV patients

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17
Q

What is Potts disease?

A

Destruction of the intervertebral space and adjacent vertebral bodies - collapse of the spinal elements

Anterior wedding leading to kyphosis and gibbus formation

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18
Q

What is gibbus formation?

A

anterior collapse of one or more vertebral bodies resulting in kyphosis

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19
Q

Where in the spine does TB tend to affect and what imaging should you use?

A

Thoracic then lumbar

Whole spine MRI (note evidence to support this in TB disci tis but not pyogenic discitits)

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20
Q

What are the features of GI TB?

A

Crossover with histology of TB
1/3 patients can present with acute abdomen and perforation - doughy abdomen with RIF mass
Pulmonary TB concurrently in 30%

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21
Q

What are the two most common manifestations of TB in the skin?

A

Erythema nodosum
Lupus Vulgaris

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22
Q

What are the routine investigations for TB?(6)

A

Routine bloods
BBV screen - hep B, hep C, HIV
Diabetes - HbA1c

CXR
Low threshold Brain/Spinal imaging

Blood culture if suspecting military TB

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23
Q

Features of TB bacteria microbiology? (6)

A

Rod shaped bacilli
Acid Fast
Multiplies slowly 18-24h
Thick lipid wall
Aerobic
Non motile

24
Q

Diagnosis of TB (3)

A

Culture - Lowenstein Jensen medium
Gene Xpert PCR
Acid Fast Sputum Smear

25
How do TB colonies look on LJ medium?
Brown granular colonies - buff rough and tough SLOW growing
26
First line TB treatment
Rifampicin Isoniazid + pyridoxine (B6) Pyrazinamide Ethambutol
27
Treatment for CNS TB
12 months 2m RIPE 10m RI
28
Name the TB Medication from side effect - hepatotoxicity
Isoniazid Rifampicin Pyrazinamide
29
Name the TB Medication from side effect - ocular toxicity
Ethambutol
30
Name the TB Medication from side effect - peripheral neuropathy
Isoniazid (vitamin b6)
31
Name the TB Medication from side effect - Gout
Pyrazinamide
32
Name the TB Medication from side effect - Drug induced fever
Rifampicin
33
Name the TB Medication from side effect - Drug induced Lupus
Isoniazid
34
Name the TB Medication from side effect - Drug induced fever
Riffampicin
35
Name the TB Medication from side effect - CYP450 enzyme inducer
Rifampicin Therefore decreases activity of drugs metabolised by CYP450
36
How does TB bacilli look in aura mine phenol stain?
Yellow against dark background (using fluorescent microscope)
37
What are the issues with LJ lab growing TB?
Slow and expensive (4-8 weeks, liquid media 3 weeks)
38
Biopsy/histopathology of TB granulomas?
Caseating granulomas Multi-nucleated cells with nuclei arranged like a horseshoe (langerhans giant cell) and foreign body giant cells ## Footnote Fused macrophages (giant cell) which are generated in response to the presence of a large foreign body. Foreign body giant cells are also produced to digest foreign material that is too large for phagocytosis. The inflammatory process that creates these cells often leads to a foreign body granuloma.
39
Describe process of TST (Tuberculin skin test)
0.1ml of 5TU PPD tuberculin injected intradermally Induration in mm read after 48h Issues include variability admin and reading and >1 visit needed AND cross reaction with BCG
40
Which patient groups to check for latent TB
HIV Children <5 Low TB incidence countries - all household contacts Initiating anti TNF Tx Dialysis patents Prep to organ transplant Patients with silicosis
41
Definition of treatment disruption
More than 14 days - restart from beginning Less than 14 days - can just be continued
42
Paradoxical TB reaction
IN commencing of treatment can get lots of cytokine release --> worsening of symptoms Particular concerning if brain/heart disease - steroids needed (dex for brain, pred for perdicardial disease)
43
When to stop TB drugs in hepatotoxicity?
If AST/ALT is >5 times normal limit OR AST/ALT 3x limit with symptoms Concern if bili up (Hys law) If severe should change to ethambutol fluroquunolone, linezolid
44
How to restart TB drugs following liver hepatotoxicity?
Restart every 3-7 days EMB and RIF Then INH Then PZA
45
What are the two patterns of liver toxicity?
Early (within 2-3 weeks) - good prognosis usually RIF/INH Later (after 1 month) usually PZA - bad prognosis
46
What is mono resistant TB?
resistance to 1 drug isoniazid resistance 7% cases
47
What is MDR TB?
Resistant to rifampicin and isoniazid
48
What is XDR TB (Extensively resistant)?
MDR + resistance to fluroquinines + one additional group A drug (bedaquilin or linezolid)
49
What are group A TB drugs?
Fluroquinolones (Levifox or moxiflox) Bedaquiline Linezolid
50
What is pre XDR TB??
MDR TB and resistance to fluoroquinolones
51
What is relationship between Rif resistant TB and MDR TB?
90% rif resistant are iso resistant --> surrogate marker Another benefit of gene xpert
52
Relationship between HIV and TB immunologically
Activates Tells and supports HIV replication Increased HIV viral load Risk of active TB increased In turn HIV limits macrophage ability to restrict the growth of TB bacilli TB is the most common OI in HIV positive people
53
Issues of treatment of HIV and confection TB
Cumulative drug toxicities High pill burden IRIS
54
Public health approach to TB
Intensified case finding Infection control for TB Isoniazid prevention therapy
55

DTMH (15 decks)

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