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DTMH > TB > Flashcards

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
Q

How do TB colonies look on LJ medium?

A

Brown granular colonies - buff rough and tough

SLOW growing

26
Q

First line TB treatment

A

Rifampicin
Isoniazid + pyridoxine (B6)
Pyrazinamide
Ethambutol

27
Q

Treatment for CNS TB

A

12 months
2m RIPE
10m RI

28
Q

Name the TB Medication from side effect - hepatotoxicity

A

Isoniazid
Rifampicin
Pyrazinamide

29
Q

Name the TB Medication from side effect - ocular toxicity

A

Ethambutol

30
Q

Name the TB Medication from side effect - peripheral neuropathy

A

Isoniazid (vitamin b6)

31
Q

Name the TB Medication from side effect - Gout

A

Pyrazinamide

32
Q

Name the TB Medication from side effect - Drug induced fever

A

Rifampicin

33
Q

Name the TB Medication from side effect - Drug induced Lupus

34
Q

Name the TB Medication from side effect - Drug induced fever

A

Riffampicin

35
Q

Name the TB Medication from side effect - CYP450 enzyme inducer

A

Rifampicin

Therefore decreases activity of drugs metabolised by CYP450

36
Q

How does TB bacilli look in aura mine phenol stain?

A

Yellow against dark background

(using fluorescent microscope)

37
Q

What are the issues with LJ lab growing TB?

A

Slow and expensive
(4-8 weeks, liquid media 3 weeks)

38
Q

Biopsy/histopathology of TB granulomas?

A

Caseating granulomas
Multi-nucleated cells with nuclei arranged like a horseshoe (langerhans giant cell) and foreign body giant cells

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
Q

Describe process of TST (Tuberculin skin test)

A

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
Q

Which patient groups to check for latent TB

A

HIV
Children <5
Low TB incidence countries - all household contacts
Initiating anti TNF Tx
Dialysis patents
Prep to organ transplant
Patients with silicosis

41
Q

Definition of treatment disruption

A

More than 14 days - restart from beginning
Less than 14 days - can just be continued

42
Q

Paradoxical TB reaction

A

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
Q

When to stop TB drugs in hepatotoxicity?

A

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
Q

How to restart TB drugs following liver hepatotoxicity?

A

Restart every 3-7 days

EMB and RIF
Then INH
Then PZA

45
Q

What are the two patterns of liver toxicity?

A

Early (within 2-3 weeks) - good prognosis usually RIF/INH

Later (after 1 month) usually PZA - bad prognosis

46
Q

What is mono resistant TB?

A

resistance to 1 drug
isoniazid resistance 7% cases

47
Q

What is MDR TB?

A

Resistant to rifampicin and isoniazid

48
Q

What is XDR TB (Extensively resistant)?

A

MDR + resistance to fluroquinines + one additional group A drug (bedaquilin or linezolid)

49
Q

What are group A TB drugs?

A

Fluroquinolones (Levifox or moxiflox)
Bedaquiline
Linezolid

50
Q

What is pre XDR TB??

A

MDR TB and resistance to fluoroquinolones

51
Q

What is relationship between Rif resistant TB and MDR TB?

A

90% rif resistant are iso resistant –> surrogate marker

Another benefit of gene xpert

52
Q

Relationship between HIV and TB immunologically

A

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
Q

Issues of treatment of HIV and confection TB

A

Cumulative drug toxicities
High pill burden
IRIS

54
Q

Public health approach to TB

A

Intensified case finding
Infection control for TB
Isoniazid prevention therapy

DTMH (15 decks)

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