19 Mycobacterial diseases

Question 1

How are mycobacteria different to all other bacteria? (4)

Answer 1

Waxy cell wall- high lipid content.
Slow growing.
Poor gram staining (ghost cells).
Acid fast bacilli (Ziehl Neelsen, Phenol Auramine).

Question 2

Name three atypical mycobacteria:

Why are they atypical?

Answer 2

M. avium.
M. kansasii.
M. marinum.
Lack of person-person transmission.

Question 3

What is primary tuberculosis? (4)

Answer 3

Usually in periphery of mid zone lung.
Inhaled bacilli phagocytosed by macrophages. Gohn focus in hilar lymph nodes.
Intracellular multiplication and dissemination.

Question 4

Describe tubercle formation (the body’s response to primary TB):

Answer 4

Cell mediated granuloma formation.
Central area of epitheliod and giant cells (capable of TB killing).
Central area of caseous necrosis, fibrosis and calcification.
Surrounding lymphocytic infiltration.
May remain viable for 20 years.

Question 5

When does reactivation Tuberculosis occur? (8)

Answer 5

Lowered immunity.
Western: 50yo men.
Malnutrition/alcoholism/debilitating illness.
HIV infection.
Silicosis, chronic renal failure, gastrectomy.
Anti TNFα blockade (infliximab).

Question 6

How does TB reactivate and where does it do it?

Symptoms? (5)

Answer 6

Tubercles coalesce and cavitate.
Lung apices (oxygen tension).
Chronic productive cough, haemoptysis, weight loss, fever, night sweats.

Question 7

What are the symptoms of TB meningitis? (6)

Answer 7

Insidious onset
Unidentified fever
Personality change
Focal neurological deficit
Mild meningism.
May lack constitutional quartet.

Question 8

What is the constitutional quartet associated with TB?

Answer 8

Fever.
Night sweats.
Anorexia.
Weight loss.

Question 9

How is TB diagnosed using microbiology? (4)

Answer 9

3 early morning sputum specimens.
Direct microscopy for AFBs.
Lowenstein-Jensen culture (3-4wks).
Broth culture

Question 10

Whys is PCR used less than culture for TB diagnosis? (3)

Answer 10

Less sensitive than culture.
Expensive.
Not 100% specific.

Question 11

What is the Xpert MTB/RIF test?

Answer 11

Direct to sputum, 2hr result.

Highly specific and sensitive.

Question 12

What is the treatment for standard pulmonary TB?

Meningeal?

Answer 12

First 2months: isoniazid, rifampicin, pyrazinamide, ethambutol. Next 4 months: isoniazid, rifampicin.

12 months + initial corticosteroids

Question 13

Which drugs are MDR and XDR resistant to?

2, 3

Answer 13

MDR: isoniazid + rifampicin.
XDR: fluoroquinolone + isonazid + rifampicin.

Question 14

Which are the new drugs with shorter treatment times for TB? (3)

Answer 14

Bedaloquine.
Delamanid.
Pa-824.

Question 15

What tests are available for TB? (3)

Answer 15

Mantoux test.
Interferon gamma release assays.
TB specific antigens: ESAT6 and CFP10.

Question 16

What is the BCG vaccine and who is it given to? (2)

Answer 16

Attenuated M bovis stain.

Neon or exposure risk.

Question 17

What does Mycobacterium avium cause? (3)

Treatment?

Answer 17

Disseminated disease in HIV +ve.
Pulmonary TB.
Cervical lymphadenitis in children.
Macrolide: clarithromycin/ azithromycin.

Question 18

What does Mycobacterium leprae cause? (w types)

Answer 18

Tuberculoid - macules/plaques, ulnear/common peroneal nerve.

Lepromatous - subcutaneous tissue accumulation, leonine facies.

Question 19

How is Mycobacterium leprae treated? (3)

Answer 19

Dapsone.
Rifampicin.
Clofazimine.

Question 20

What is miliary TB?
How does it occur?
Who in?

Answer 20

Extra-pulmonary + disseminated.
Erosion of necrotic tubercle into blood vessel.
Very young/old, immunocompromised.

Question 21

Where are the extra-pumnoary sites of TB spread? (8)

Answer 21

Pleura
Lymph nodes
Kidneys
Epididymis
Bone
Intestines
Brain / meninges
Pericardium.