Tuberculosis And Asthma Flashcards by Maya White

What are the 3 most common bacteria associated with human TB??

Mycobacterium tuberculosis
Mycobacterium bovids
Mycobacterium africanum

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Describe some features of mycobacterium tuberculosis

Non-motile
Rod-shaped
Obligate aerobe
Has a very thick layer of fatty acids, glycolipids etc
Need Acid-Fast stain (cannot stain with Gram stain)

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Why does mycobacterium TB take a long time to culture?

Relatively slow growing bacteria
Generation time 15-20 hours
Takes a minimum of 2 weeks to culture

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How is TB spread?

Respiratory droplets (coughing/sneezing) 
Infectious dose is very low 
Air remains infectious for 30 minutes

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Is it easy to catch TB?

Usually need prolonged exposure to catch it

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What are the classic situations in which TB spreads?

Overcrowding situations:
Poor housing
Prisons
Homeless people

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Describe the pathogenesis of TB

Inhaled aerosols/droplets
Engulfed by alveolar macrophages
Drainage of lung to local lymph nodes
Primary complex/focus of infection established
Progression to primary active disease or initial containment of infection to latent

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What are the 2 outcomes of latent infection?

Heals/self cure

Reactivation of post-primary TB

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What is the commonest type of TB?

Reactivation of latent to post-primary TB

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Describe how tests for latent TB would appear

TST (mantoux) and IFN gamma tests would be positive
Chest x-ray normal
Sputum smears and cultures normal
Asymptomatic

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What are the main symptoms of active TB

Cough
Fever
Weight loss

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What is miliary TB?

TB disseminated wide into the body via the blood stream
(Tiny spots throughout lung fields on x-ray)
Rare

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What are some of the risk factors for reactivation?

HIV 
Substance abuse
Prolonged corticosteroid therapy 
Immunosuppressants 
TNF alpha antagonist 
Low body weight 
Organ transplant 
Haematological malignancy 
Severe kidney disease
Diabetes mellitus 
Silicosis

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What are caseating granulomata in TB?

Lung parenchyma and lymph nodes
Liquified and cheesy looking material
Dead and dying bacilli and inflammatory cells
Langhan’s giant cells present

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What are the common sites for extrapulmonary TB?

Larynx 
Lymph nodes
Kidneys 
Pleura
Brain 
Bones and joints

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What are some risk factors for TB

Non-Uk born/recent migrants
HIV infected
Immunocompromised
Homeless
Drug users
Prisoners 
Close contacts of patients with TB 
Young adults

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What Hx would suggest TB?

Recent arrival/travel
Contacts with TB 
BCG vaccination?
Fever
Weight loss
Malissa
Anorexia

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List some symptoms of pulmonary TB

Fever
Night sweats 
Weight loss/anorexia 
Tiredness
Malaise
Cough 
Haemoptysis 
Breathlessness

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What are some signs on examination of pulmonary TB?

Fever
Often no chest signs 
CXR abnormality 
May be crackles in infected areas 
(Pleural involvement = dullness)

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What investigations would you run for TB??

CXR
Sputum - 3 early morning samples
Induced sputum via physiotherapy
Bronchoscopy

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What would you see on a CXR for TB?

Apex of the lung often involved
Ill defined patchy consolidation
Cavities can develop in consolidation
Healing results in fibrosis

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Why are sputum smears not very good in diagnosing TB?

Not very sensitive
May only have a few bacilli in
Operator dependents

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What is the gold standard investigation for diagnosis of TB?

Culture (but takes approximately 2 weeks)

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What are epitheloid cells?

Activated macrophages

Can fuse together to form giant cells

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Describe the tuberculin sensitivity test (TST)/mantoux

Look for latent TB Challenge with an antigen previously exposed to Infected intra-dermally Inflammation, red circle appear at injection site Read 2-3 days later (Can get false positives and false negatives)

Describe interferon gamma releasing assays (IGRAs)

Buffer test for latent TB Blood test No cross reaction with BCG Cannot distinguish between latent and active TB

What is the first line medication for TB?

``` 4 first line medications: Rifampicin Isoniazid Pyrazinamide Ethambutol ```

What are some problems with Rifampicin?

Can give orange secretions (tears/urine) | Cannot take whilst on the contraceptive pill

What is the bad side effect of ethambutol?

Can cause visual disturbance

What are the second line drugs for TB?

Quinolones Clofazamine PAS Ethionamide

Why do we always use a combination of drugs to treat TB?

TB is notorious for producing mutations | Don't want to select for a particular strain

What is the minimum course of treatment for TB?

6 months

What is scrofula?

A lymphadenitis Disease with glandular swellings Probably a form of TB

Give some common clinical signs of extrapulmonary TB

Lymphadenitis Ascites Adhesions of peritoneum Pott's disease

What is Pott's disease?

A form of TB where disease is seen in the vertebrae

Name some of the TB prevention methods

All forms of TB must be notified to public health Personal protective equipment Negative pressure isolation Susceptible people vaccinated

Describe BCG vaccine

Live vaccine From mycobacterium bovis strain Given to babies in high prevalence communities 70-80% effective

What is asthma?

Chronic inflammatory disorder of the airways | Reversible airway obstruction caused by inflammation, bronchoconstriction and mucus

Describe what happens during an asthma attack

Environmental trigger breathed in Inflammation driven by TH2 cells Type 1 hypersensitivity reaction (immediate) Airway narrowing - SM contraction, mucus production and inflammatory cell infiltration

Is asthma restrictive or obstructive?

Obstructive

What would the FEV1/FVC look like in asthma?

Before treatment = FEV1 reduced, FVC normal | After treatment = FEv1 and FVC normal

Why is it difficult to diagnose asthma?

There is no standardisation of type, severity, frequency, symptoms or investigation findings (Everybody gets it differently)

What are the reversible symptoms of asthma?

Wheeze Breathlessness Chest tightness Cough

What is a wheeze?

High pitched Expiratory musical sound From narrowed airways

Describe the typical features of a cough due to asthma

Worse at night Dry Exercise induced Non-productive

Give some clinical signs of asthma

``` Respiratory rate increase Tracheal tug Recession Nasal flaring Accessory muscle use ```

Give some features of a typical Hx for asthma

Eczema, hay fever etc (atopy) Smoker/smoking in home Mould in home/live on farm/pets

Describe the peak flow of an asthmatic patient

Varies over the day Diurnal variation Treatment stabilises this a lot Should increase after inhaler use

What do we measure with spirometry?

FEV1 | FVC

What do we do first for someone with suspected asthma?

Trial them on bronchodilators for 1 month then review | See if symptoms and peak flow gets better

Give some prevention methods for asthma

Change pillows and bedsheets every few years Fresh air Stop smoking

What is the approach to asthma treatment?

Step up, step down | Step up to other medications if getting worse or down to less if getting better

What is the general progression of treatment for an asthmatic getting worse?

Short acting inhalers + steroid inhalers Long acting inhalers Specialist care

How does a short acting beta agonist work?

Helps to relax smooth muscle | Quick relief

When do people require a step up from short acting inhalers?

If using the inhaler more than 3 times a week | Or if nocturnal symptoms occur more than once a week

How to steroid inhalers work?

Preventer Reduces inflammation - inhibitors of inflammatory cells and mediators Prevents attacks

Describe the clinical features of a mild asthma attack

``` Sats >92% Pulse <110 Resp rate <25 Speech normal Minimal wheeze PEFR >75% predicted ```

Describe the clinical features of a moderate asthma attack

``` Sats >92% Pulse <110 Resp rate <25 Speech normal wheeze +++ PEFR 50-75% predicted ```

Describe the clinical features of a severe asthma attack

``` Sats <92% Pulse >110 Resp rate >25 Can't complete sentences No wheeze PEFR 35-50% predicted ```

How do you treat a severe asthma attack?

Give lots of salbutamol via a nebuliser | With a continuous stream of oxygen

Describe the clinical features of a life threatening asthma attack

``` Sats <92% (cyanosis) Silent chest/poor expiratory effort Altered consciousness Exhaustion PEFR 35% predicted ```

Why do we sometimes need to give IV salbutamol?

Sometimes the mediation struggles to get through the thick layer of mucus when in an inhaler

What is the treatment for a life threatening asthma attack?

Do the A-E assessment Be aware they may go into cardiac arrest Oxygen Salbutamol nebulisers - back to back until airways open IV access (need to cannulate ASAP) - salbutamol