- Close contact with patient infected with pulmonary TB - high prevalence in India + sub-Sahara Africa - extremes of age - homelessness - diabetes - immunosuprresion e.g. HIV - alcohol or drug dependence - prolonged steroid use

Tuberculosis Flashcards by Emily Stephens

What organism causes tuberculosis

Mycobacterium tuberculosis complex bacteria

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What organism most commonly causes TB?

Mycobacterium tuberculosis

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Describe the pathogenesis of TB

aerosols inhaled
engulfed by alveolar macrophages
at this point most have a spontaneous recovery
those who don’t > primary TB (latent or disseminated)
if latent, TB can reactive causing post primary TB

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Describe the mycobacterium tuberculosis

non motile bacilli
obligate aerobe
long chain fatty acids + glycolipids in cell wall
slow growing
acid fast bacilli

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Risk factors of TB

Close contact with patient infected with pulmonary TB
high prevalence in India + sub-Sahara Africa
extremes of age
homelessness
diabetes
immunosuprresion e.g. HIV
alcohol or drug dependence
prolonged steroid use

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Risk factors for reactivation of TB

infection with HIV
substance abuse
prolonged therapy with corticosteroids
organ transplant
diabetes mellitus
low body weight
severe kidney disease
anti TNF treatment

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Why can gram stain not be used for mycobacterium tuberculosis?
What is used instead?

Gram satin cant go through thick fatty acid cell wall
ZN staining

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What are the three types of TB disease?

Pulmonary TB
Extrapulomary TB
Miliary TB

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Site of miliary TB

Carried to all parts of the body through bloodstream

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Who is extrapulmonary TB often found in?

HIV infected
Immunosuppressed
Young children

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Symptoms of pulmonary TB

fever
night sweats
weight loss/anorexia
fatigue
cough
haemoptysis
malaise
breathlessness if pleural effusion

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Signs of pulmonary TB on examination

often no chest signs despite CXR abnormalities
crackles in affected area

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Extrapulmonary presentation of TB

erythema nodosum
meningitis
lymphadenopathy
pericardial effusion
cold abscess

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What is a cold abscess in TB?

a firm painless abscess, often in the neck

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Investigation of pulmonary TB

CXR
consider CT chest if CXR not typical
histology
if productive cough, 3x ZN stain + TB culture
Mantoux test
Interferon-gamma release assay
NAAT

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How does a TB infection appear on CXR?

often at apex
ill defined patchy consolidation
cavitation within consolidation
healing results in fibrosis

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What is a ghon focus?
How does it form?

spherical granuloma with central caseation, caused by the macrophages ingesting Mycobacterium tuberculosis
three weeks after infection, immune cells surround site of infection > granuloma
this isolates bacteria to prevent spreading
tissue inside granuloma dies > caseous necrosis
the necrotic area is a ghon focus

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What is a ghon complex?

to infection spread to hilar lymph nodes
the caseating tissue (ghon focus) + associated lymph node is the ghon complex

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What can be done if a suspected TB patient isn’t producing enough sputum for culture?

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sputum induction with nebulised hypertonic saline
bronchoscopy + bronchoalveolar lavage

Diagnosis of TB

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sputum/blood cultures (gold standard) but can take months so nucleic acid amplification tests done as it is faster

Outline nucleic acid amplification tests

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assess for genetic material of pathogen
performed on sputum sample
provides info about bacteria faster than a culture

What is NAAT used for?

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diagnosing TB in patients with HIV or under 16

Diagnosing latent TB

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Mantoux test (tuberculin skin test)
Interferon Gamma Release Assay

Outline the Mantoux Test

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injecting tuberculin into the intradermal space on the forearm
infection creates a bleb under the skin
the bleb is measured after 72 hours
> 5mm is positive

Outline interferon-gamma release assays

- mixing a blood sample with M.tuberculosis antigens - if there is a previous infection, WBCs will release interferon-gamma - positive result if interferon-gamma is released

Where is TB common?

Africa Asia Latin America

How does post primary TB arise?

Reactivation of latent infection

What does primary TB lead to?

- **asymptomatic latent TB** (more common) - **primary progressive pulmonary/extrapulmonary TB** through dissemination

Main sites of extrapulmonary TB

- CNS - pleura - bones + joints - urogenital tract

What is miliary TB?

Form of TB characterised by widespread dissemination to extrapulmonary organ causing tiny lesions

What is suggestive of miliary TB on chest x ray?

Many tiny spots throughout lung field

What do all patients with miliary TB need + why?

**CT/MRI head +/- LP** to exclude CNS involvement *e.g. TB meningitis/CNS TB*

Lumbar puncture results of TB meningitis/CNS TB

high protein low glucose lymphocytosis

What vaccination is given to prevent TB? Describe it What must be done before the vaccine?

- **BCG vaccine** - intradermal injection of live attenuated mycobacterium bovis > creates immune response + immunity to M.tuberculosis - tested with Mantoux test, risk of immunosuppression + HIV

Who is the TB vaccine given to?

- those at increased risk of TB - healthcare workers

Treatment of latent tuberculosis

*isoniazid* + *rifampicin* for 3 months OR *isoniazid* for 6 months

First line medication for active TB How long must each be taken for?

*Rifampicin*: 6 months *Isoniazid*: 6 months *Pyrazinamide*: 2 months *Ethambutol*: 2 months . take all for 2 months and then continue for 4 months with just *rifampicin* + *isoniazid*

Management of TB

- notify public health England - admit to negative pressure side room + start infection control measures - routine bloods (especially LFTs) - HIV test - screening + tracing of close contacts - medications: *isoniazid, rifampicin, pyrazinamide + ethambutol*

Due to certain side effects of TB drugs, what must be done before and during treatment?

- risk of hepatitis + visual disturbances - baseline LFTs + visual acuity tests - monitor both whilst on treatment

Side effects of *rifampicin*

Orange urine/secretions Hepatitis Thrombocytopaenic rash

side effects of isoniazid

- hepatitis - rashes - peripheral neuropathy - psychosis - drug induced SLE

Side effects of pyrazinamide

- hepatitis - rashes - vomiting - arthralgia

Side effects of ethambutol

visual disturbances

What must always be given with isoniazid? Why?

**pyridoxine** (vit B6) Avoid damage to peripheral nerves

What skin findings can arise with TB?

Erythema nodosum

Pulmonary complication for TB

- pleurisy - plural effusion - empyema - pneumothorax - bronchiectasis - respiratory failure

Investigations + management of respiratory TB

- admit to side room + start infection control measures - if productive cough > x3 sputum samples for ZN staining + TB culture - if non productive > consider bronchoscope or nebulised hypertonic saline - routine bloods incl HIV + vitamin D - NAAT for mycobacterium tuberculosis - if positive > start anti TB therapy - isoniazid, rifampicin, ethambutol, pyrazinamide

Tuberculosis Flashcards

(47 cards)