tuberculosis

Question 1

what is tuberculosis?

Answer 1

it’s an infectious disease caused by Mycobacterium tuberculosis, a small rod-shaped bacteria (a bacillus).

Question 2

describe 3 characteristics of
the M. tuberculosis bacteria.

Answer 2

• slow dividing
• high oxygen requirements
• difficult to culture in the lab

Question 3

what is the disadvantage of m. tuberculosis waxy coat?

Answer 3

makes gram staining ineffective

Question 4

acid-fast bacilli meaning

Answer 4

resistant to acids used in staining procedures

Question 5

what special stain is used and what does it do?

Answer 5

Zeihl-Neelsen stain
turns bright red against blue background

Question 6

what is Multidrug-resistant TB (MDR-TB)?

Answer 6

strains resistant to more than one TB drug e.g., isoniazid and rifampicin

difficult to treat.

Question 7

how is TB spread?

Answer 7

inhaling saliva from infected people

Question 8

describe 4 outcomes of TB

Answer 8

Immediate clearance of the bacteria

Primary active tuberculosis (active infection after exposure)

Latent tuberculosis (presence of the bacteria with no symptoms and not contagious)

Secondary tuberculosis (reactivation of latent tuberculosis to active infection)

Question 9

When does disseminated/ severe miliary TB develop?

Answer 9

when the immune system can’t control the infection

Question 10

describe latent TB

Answer 10

Latent tuberculosis is present when the immune system encapsulates the bacteria and stops the progression of the disease.

Question 11

when does secondary TB happen?

Answer 11

When latent tuberculosis reactivates

Question 12

what’s a cold abscess?

Answer 12

a firm, painless abscess caused by tuberculosis, usually in the neck.

They don’t have the inflammation, redness and pain you expect from an acutely infected abscess.

Question 13

what are some risk factors?

Answer 13

• Age: Elderly, Neonates
• Co-Morbidity: Diabetes, HIV, Malnutrition
• Immunosuppression
• Social: homeless, alcohol dependency, drug use, mental health problems

Question 14

describe the BCG vaccination

Answer 14

Bacillus Calmette–Guérin (BCG) vaccine involves an intradermal injection of live attenuated (weakened) Mycobacterium bovis bacteria (a close relative of M. tuberculosis that does not cause disease in humans).

This creates an immune response, providing lasting immunity against M. tuberculosis without causing infection.

The vaccine protects against severe and complicated TB but less against pulmonary TB.

Before vaccination, patients need to have a negative Mantoux test.

They are also assessed for the possibility of immunosuppression and HIV due to the risks related to a live vaccine.

It is offered to patients at increased risk of TB

Question 15

what are the7 typical symptoms of TB?

Answer 15

Cough

Haemoptysis (coughing up blood)

Lethargy (lack of energy and enthusiasm)

Fever or night sweats

Weight loss

Lymphadenopathy (lymph nodes swelling)

Erythema nodosum (tender, red nodules on the shins caused by inflammation of the subcutaneous fat)

Question 16

what are the 5 extrapulmonary presentations of TB?

B+J, M, L SL, ST

Answer 16

• Bones and Joints (insidious onset, pain especially at night, swelling, pyrexia, decreased range of motion)
• Lymphadenopathy (painless and rubbery)
• Meningism (if spread to CNS)
• Spinal tuberculosis (Pott’s disease: with kyphosis and cold abscesses which are firm and painless lump on the neck)
• Skin lesions (e.g. erythema nodosum, scrofuloderma/ulcerated skin abscess)

Question 17

what investigations are used for latent TB?

Answer 17

Interferon-Gamma Release Assays
Mantoux test

Question 18

describe the Interferon-Gamma Release Assays

Answer 18

• This involves mixing a blood sample of the patient with mycobacteria tuberculosis bacteria
• the test is positive if there is release of interferon-gamma by white blood cells.

Question 19

describe the mantoux test

Answer 19

• less reliable than IGRA
• an induration of ≥5 mm is a positive result
• involves an intradermal injection of tuberculin (collection of tuberculosis proteins) which then forms a bleb, this is then measured after 3 days.

Question 20

What investigations are used for active TB?

Answer 20

chest x-rays and cultures samples

Question 21

What will primary, reactivated and disseminated miliary TB show on a chest x-ray?

Answer 21

Primary tuberculosis
- patchy consolidation, pleural effusions and hilar lymphadenopathy.

Reactivated tuberculosis
- patchy or nodular consolidation with cavitation (gas-filled spaces), typically in the upper zones.

Disseminated miliary tuberculosis
- multiple bilateral small opacities that resemble millet seeds

Question 22

Describe different ways you can collect a sputum sample

Answer 22

Sputum cultures
3 separate sputum samples are collected, 8-24 hours gap, at least 1 early morning sample to culture for sensitivity

Mycobacterium blood cultures (require special blood culture bottle)

Lymph node aspiration or biopsy

Question 23

How do you treat latent TB?

Answer 23

Isoniazid and rifampicin for 3 months

Isoniazid for 6 months or

Rifampicin for 6 months

Question 24

How would you treat active TB?

Answer 24

R – Rifampicin for 6 months
I – Isoniazid for 6 months
P – Pyrazinamide for 2 months
E – Ethambutol for 2 months

Question 25

What are the side effects of these medications?

Answer 25

Rifampicin
- red/orange discolouration of secretions, such as urine and tears.
- It is a potent inducer of the cytochrome P450 enzymes and reduces the effects of drugs metabolised by this system, such as the combined contraceptive pill.

Isoniazid
- peripheral neuropathy.
- Pyridoxine (vitamin B6) is co-prescribed to reduce the risk.

Pyrazinamide
- hyperuricaemia (high uric acid levels), resulting in gout and kidney stones.

Ethambutol
- colour blindness and reduced visual acuity.

Rifampicin, isoniazid and pyrazinamide are all associated with hepatotoxicity and hepatitis