Tuberculosis

Question 1

Describe the process of primary tuberculosis infection and dissemination including the causative organism.

Answer 1

Primary Infection: (usually asymptomatic but may cough, which spreads large quamtities of mycobacterium)

A mycobaterium tuberculosis/bovis/africanum is inhaled in droplets.

Host macrophages engulf the mycobaterium and carry it to hilar lymph nodes in attempt to control the infection.

Some mycobacterium disseminate around the body via the lymphatics and bloodstream.

Granulomas (tubercules) form around the disseminated organisms in an attempt to control the infection. (type IV immune response)

Outcomes:
80% of people heal spontaneously, the body fights off and clears the infection.
20% of people the granulomas contain the infection but it is not cleared- it is dormant (not infectious and causing no harm)

A small proportion of those with dormant Tb will develop secondary active Tb infection.

Question 2

Discuss the presentations of post primary infection of Tb from reactivation?

Answer 2

Miliary Tb
If the infection is not properly capsulated it can disseminate into the bloodstream. Severe infection; can affect virtually anywhere in the body.

Secondary Tb
Reactivation of previously dormant Tb. Usually affects the apices of the lung causing pulmonary Tb which may spread locally or distally.

Question 3

Outline the common predisposing factors?

Answer 3

Being from or travel to an area with endemic TB
Immunocompromised (HIV)
Alcoholism
Non-Caucasian
Social deprivation/overcrowded living conditions
Known contacts of TB

Question 4

Outline the investigations you would do for someone you suspect may have Tb?

Answer 4

Bloods:
FBC
U/e's
LFTs
CRP
Blood culture (ZN stain)
Sputum spear with ZN staining to help confirm
Sputum culture- takes 1-3wks

CXR- upper lobe cavitations, pleural effusions
-if military TB- millet seeds uniformly distributed throughout lung fields

Other:
Mantoux test
- to look for previous immune response against TB

Interferon gamma asy

• blood sample and mix with antigens from TB bacteria
• if previous TB WBC will release interferon gamma
• if +ve mantoux but no features of active infecton

Question 5

Describe the presentation of non pulmonary Tb?

Answer 5

Lympathendopathy

CNS: Tb meningitis

Pericardium: Pericarditis and pericardial effusion

Adrenals: Adrenal destruction mimicking addisons

GI: Ileocaecal obstruction or crohns like symptoms, abcess formation (psoas)

GU: Insidious renal symptoms: polyuria, nocturia and dysuria.

Skeletal: Peripheral joint pain and spine pain (potts disease)

Millary Tb will present with night sweats, pyrexia and wt loss.

Question 6

How are confirmed cases of TB treated?

Answer 6

6 months of isoniazid and rifampicin.
Supplemented in the first 2 months with pyrazinamide and ethambutol

RIPE

Rifampacin
Isoniazid
Pyrazidamine
Ethambutol

Question 7

Who should receive contact tracing for Tb?

Answer 7

Offer Mantoux testing to diagnose Latent TB in people who are:
-either household contacts
OR
-close work or school contacts

Of all patients diagnosed with active TB

Question 8

How is latent TB treated?

Answer 8

6 month course of isoniazid

OR

3 month course of rifampacin and isoniazid

Question 9

Why is there such an issue with multi drug resistant TB?

Answer 9

As there is such a huge bacterial load bacterial courses are very long.

There can be issues with compliance due to this as patients start to feel better before the course is finished.

Due to this there are multi drug resistant (MDR) strains that are resistant to both Rifampicin and isoniazid.

Question 10

What methods are used to try and reduce the incidence of MDR TB?

Answer 10

Triple/quadruple therapy.

DOT schemes (directly observed therapy) this is used in patients where it is thought compliance may be an issue such as homeless people that do not have a fixed residence)

Question 11

How is MDR TB treated?

Answer 11

5 drugs are used for up to a period of 2 years.

During this time patients are in specialist quarantined rooms with negative air pressure to prevent spread of the infection.

Antibiotics which are trialled are:

• high-dose isoniazid, pyrazinamide, and ethambutol
• quiniolones: levofloxacin
• capreomycin, kanamycin
• bedaquiline

Question 12

What are the symptoms of TB?

Answer 12

Persistent productive cough with purulent sputum.
Haemoptysis
SOB and pleuritic pain. 
Fever
Night sweats
Weight loss
Lethargy
Anorexia 
Erythema nodosum 

Can also cause: lobar collapse, and pleural effusions.

Question 13

What are side effects of isonazid?

Answer 13

Peripheral neuropathy
Hepatitis
Agranulocytosis

Question 14

What are side effects of Rifampicin?

Answer 14

Enzyme inducer
Orange secretions
Flu like symptoms
Hepatitis

Question 15

What are side effects of ethambutol?

Answer 15

Optic neuritis

Question 16

What are side effects of pyrazinamide?

Answer 16

Gout
Arthralgia and myalgia
Hepatitis