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September lectures yr 3 (2018) > Tuberculosis > Flashcards

Flashcards in Tuberculosis Deck (23)
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1
Q

What can happen to the spine in children suffering from TB?

A

Complain of back pain - spine can stick out due to collapse of some of the vertebrae
- crumbling vertebrae occurs over weeks - help to prevent rapid paralysis

2
Q

What stain is used for TB?

A

Ziehl-Neelson stain - mycobacteria doesn’t have a peptidoglycan cell wall therefore gram staining doesn’t work

3
Q

What are the organisms that cause TB?

A

Mycobacterium Tuberculosis

- group of organisms, M. TB complex cause TB: M. tb, M bovis, M africanum, M microti, M canetti

4
Q

How is TB transmitted?

A

inhalation of infectious droplets - cough, sneeze, shout, sing
- it cannot be passed from the brain to someone else

5
Q

What factors influence the probability of TB being transmitted?

A

Infectiousness of case (number expelled into the air)
Environmental factors affecting concentration (air flow)
Proximity, frequency, duration of exposure (work, home)
Susceptibility of exposed person

6
Q

What is the difference between latent and active TB?

A

About 1/3 world pop has latent TB but they don’t suffer symptoms and can’t pass it on
10% can’t control their TB so it becomes active
If it enters the blood it can spread anywhere

7
Q

What is the pathophysiology of latent TB?

A

Macrophages ingest tubercles to form granulomas
2-8 weeks after latent TB infection it can be detected by TST or interferon-gamma release assay
Immune system able to stop multiplication and control infection
Pts not infectious and asymptomatic
Risk of reactivating
- 10% over lifetime
- 10% per year if untreated HIV
- risk is higher in children under 5 and immunosuppressed

8
Q

What is the pathophysiology of active TB?

A

Granulomas breakdown and bacilli escape/multiply
May occur at time of original infection or years later
Open/Pulmonary TB is infectious
Extrapulmonary TB is usually not infectious
Symptoms:
- cough (if pulmonary)
- fever
- night sweats
- weight loss
- local symptoms (back pain, joint pain, Lnopathy, meningitis)

9
Q

How does miliary TB present?

A

Very variable
Acute disease can be fulminant- sepsis, multiorgan failure, ARDS
Subacute/chronic (median duration= 2 months)
- general = failure to thrive, sweats, pyrexia
- Pulmonary = cough, SOB, pain, hypoxia
- Lymphatic= enlargement, airway compression
- bone/joint= pain, neurology
-GI = pain, pancreatitis, peritonitis, hepatitis
- CNS = meningitis, tuberculoma
- GU = haematuria, sterile pyuria, cystitis, hydronephrosis, scrotal pain, menstrual abnormalities
- adrenal = <40% of cases but overt addison’s
- CV = pericarditis
- Skin = cutis miliaris disseminata

10
Q

How do you diagnose latent TB?

A

Tuberculin skin test - mantoux

Interferon gamma release assay

11
Q

How do you diagnose active TB?

A

Clinical awareness
Radiological appearances
Microbiological samples - grow TB (sputa, CSF, vbiospy), PCR
Histology - caseating granulomas, AFBs (acid fast bacillus)

12
Q

What do the results of a mantoux test show?

A
<6mm = negative 
>6mm = positive if not BCG 
>/= 15mm positive if BCG
13
Q

How does the IGRA test work?

A

Helps to diagnose latent TB
Benefit of not cross-reacting with BCG and largely unaffected by previous infection with NTM
Surrogate marker for MTB indicating a cellular response to MTB - cannot distinguish between latent and active
>95% sensitive for diagnosis of latent TB
Poor for diagnosis of active TB
Sensitivity diminished by low CD4 count

14
Q

What are the UK recommendations for diagnosis?

A

Mantoux 1st line for latent TB diagnosis
IGRA in those with BCG borderline results
IGRA + mantoux in those with HIV and low CD4
IGRA with or without mantoux in immunocompromised
IGRA useful in hard to reach groups

15
Q

What are the problems with IGRA?

A

Variable results with serial testing - utility influenced by prevalence and BCG use
Questions of reproducibility especially if results are borderline
Expensive and need fresh blood to be rapidly processed (T-spot 8 hours of collection, quantiferon 16 hours after collection)
Interderminate results- esp. in HIV or pts on anti-TNF treatment

16
Q

What is the general principle of TB treatment?

A

Combined and prolonged drug treatment

  • multiple abx regime to prevent resistance
  • prolonged as dormant bacilli are hard to kill
17
Q

What are the problems with TB treatment?

A

non-compliance, drug resistance and side effects

18
Q

What are the treatments for TB?

A

RIPE

  • Rifampcin
  • Isoniazid
  • Pyrazinamide
  • ethambutol

Streptomycin - 1st line in developing setting

19
Q

What is the initial phase of treatment of TB?

A

4 drugs - RIPE

  • omit 4th drug if resistance is unlikely
  • given for 2 months or until abx sensitivity is known
20
Q

What is the continuation phase of treatment for TB?

A

2 Drugs to which the organism is sensitive - normally R and I
- complete 6 month treatment in total

21
Q

What are the results of TB treatment?

A

in pts who start with sensitive organism, tolerate drugs and comply with the regime, cures >98%

22
Q

How can TB be controlled?

A
Case finding 
- active - examination of family members 
- passive - education all round 
Treatment services
- especially supervision
Prevention 
- BCG immunisation 
- prophylactic use of chemo
23
Q

When to consider TB and what to do?

A

Cough >3 weeks
Fever >3 weeks
Weight loss unexplained
Night sweats

Take sputum for AFB smear and culture
Do a CXR
Ensure FU

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