Microbiology 13: Mycobacterial Diseases

Question 1

Which organism is used in the BCG vaccine ?

Answer 1

Mycobacterium. Bovis

Question 2

Describe Mycobacterium as an organism ?

Answer 2

Non-motile
Rod shaped
Waxy cell wall
Slow-growing compared to other bacteria
Acid alcohol fast
gram +ve

Question 3

Name 2 stains that pick up mycobacterium ?

Answer 3

auramine
Ziehl neelson

Question 4

Name the slow growing NTM that causes swimming pool granuloma ?

Answer 4

Mycobacterium Marinum

Question 5

Which slow growing NTM causes Buruli ulcers ?

Answer 5

Mycobacterium Ulcerans

Question 6

What are some risk factors for Non-Tuberculous Mycobacteria infections ?

Answer 6

Age
Underlying lung disease- CF, Bronchiectasis, COPD
Immunocompromised

Question 7

What are the 2 types of mycobacterium leprae?

Answer 7

• Paucibacillary tuberculoid
• Multibacillary lepromatous

Question 8

What are the main differences between Paucibacillary tuberculoid and Multibacillary lepromatous ? NB both types of Mycobacterium Leprae

Answer 8

Paucibacillary tuberculoid

• LOW in bacterial cells
• Few skin lesions
• robust Th1 cell response

Multibacillary lepromatous

• MASSIVE AMOUNT of bacterial cells
• abundance of bacilli
• multiple skin lesions
• Poor Th2 mediated cell response

Question 9

What is the primary TB granuloma in the lungs called ?

Answer 9

Ghon focus

Question 10

Which allergic reaction can be seen with primary TB ?

Answer 10

Erythema nodosum

Question 11

What is TB infection of the spine called ?

Answer 11

Pott’s disease

Question 12

Which bone is mainly affected in TB?

Answer 12

Spine - particularly affects the thoracic spine

Can get Pott’s disease

Question 13

What is Scrofula ?

Answer 13

Lymphadenitis due to TB, usually affecting the cervical lymph nodes.

Question 14

How can you test for TB in children ?

Answer 14

Gastric aspirate- children swallow their sputum

Question 15

What are the first line medications to treat TB ?

Answer 15

RIPE

For 6 months

• Rifampicin
• Isoniazid

For the first 2 months only

• Pyrazinamide
• Ethambutol

Question 16

Which TB drug causes bright orange secretions ?

Answer 16

Rifampicin

Question 17

What must you give on top of the 4 pulmonary TB meds and why?

Answer 17

• pyridoxine (Vitamin B6)
• since isoniazid can cause peripheral neuropathy otherwise

Question 18

What percentage of the world’s population are infected with TB?

Answer 18

• 33%

Question 19

What is the Most common opportunistic infection in HIV

Answer 19

TB

Question 20

Which infectious agent is the most common cause of death worldwide

Answer 20

TB

Question 21

2 classifications of post-primary TB infection

Answer 21

• Pulmonary
• Extra-pulmonary

Question 22

Key pathalogical feature of pulmonary TB and where it is most commonly found

Answer 22

• caseating granuloma (involves lots of dead necrotic macrophages with bacteria in it)
• R upper lobe most commonly

Question 23

Ix for miliary TB

Why has incidence of this type of TB increased?

Answer 23

• CXR: see millet seeds
• Increased due to HIV

Question 24

Order of stains done for ACTIVE TB

Tests for LATENT TB infection

Answer 24

Active:

• Auramine first (will fluoresce if +ve)
• If +ve, then do Ziehl-Neelsen

Latent:

• Tuberculin skin test
• IFNg release assays (used far more in UK)

Question 25

How many sputum samples to get for TB

Answer 25

3

Question 26

Medium used to culture TB

Answer 26

Lowenstein-Jensen medium

Question 27

Gold standard way to do Bacteriological Examination for TB

Answer 27

Solid and liquid culture systems - takes 1-3 weeks for results

Question 28

What can’t IGRA test disntinguish

Answer 28

If active or latent TB

Question 29

Non-TB mycobateria common in those that are immunosuppressed or those with airway structural problems (abnormal airways)

Answer 29

Mycobacterium avium complex

Question 30

Non-TB mycobateria associated with chronic lung diseases, especially in CF population

Answer 30

Mycobacterium abscessus complex

Question 31

Non-TB mycobacterium associated with swimming pool granulomas or fish tank granulomas

Answer 31

Mycobacterium marinum

Question 32

Tx for Mycobacterium Avium (non-TB mycobacterium) (4)

Answer 32

• Clarithromycin/ Azithromycin
• Rifampicin
• Ethambutol
• Amikacin/ Streptomycin

Question 33

Can mycobacterium TB live without oxygen?

Answer 33

NO - obligate aerobe so it CANNOT live WITHOUT oxygen