Myobacteria

Question 1

What type of bacteria are mycobacteria?

Answer 1

Gram positive, bacillus

Question 2

Whats different about mycobacteria to normal bacteria

Answer 2

• very waxy cell wall
• Slow growing
• poor update of gram stain ‘ghost cell’

Question 3

What is the difference between infection and disease?

Answer 3

Mycobacterium (i.e. TB) = intracellular pathogen (requires ingestion by host immune system)

Infection - host = carrier of disease but without symptoms

Disease - carrier with associated symptoms

Question 4

Is treatment for TB long or short?

Answer 4

Long - 6 moths using combinational therapeutics (prevents resistance)

Question 5

What are the bacterium that cause TB and leprosy (most of the time)?

Answer 5

M tuberculosis/M Bovis - TB

M leprae - leprosy

Question 6

Whats the main mode of transmission?

Answer 6

Respiratory droplets - most pulmonary disease

Question 7

What is mean by primary TB?

Answer 7

Acquisition of disease

Inhaled bacilli phagocytosed my macrophages (unable to kill)

Macrophages carried back to Hilar lymph nodes

Intracellular multiplication

Disseminated via lymph system/bloodstream

Question 8

Where is the most common site for primary TB in the lung?

Answer 8

Periphery of lung mid-zone

Question 9

What is it called when machrohages carry TB to Hilar lymph nodes?

Answer 9

Ghon focus

Question 10

What is the bodies response to primary TB infection?

Answer 10

Granuloma formation

• Cell mediated immune réponse - antibodies not really involved
• Central area of epithelia cell, giant cells - central region of caseous necrosis
• Fibrosis and calcification of lesions
• Bacilli slowly die/remain viable for 20 years

Question 11

What are the symptoms of primary TB?

Answer 11

Usually asymptomatic, flu like, chest X-ray = normal

• Tuberculin skin test - positive (after acquisition)

Question 12

What condition predisposes individuals to reactivation TB?

Answer 12

Immunosuppressed e.g. malnutrition, alcoholics, HIV

Individuals taking anti TNF alpha medication (immunosuppression) - infliximab

Question 13

What are the symptoms of reactivation TB?

Answer 13

Chronic productive cough (2-3 weeks) - haemoptysis

Weight loss
fever
night sweats

Question 14

What are the main characteristics of reactivation TB?

Answer 14

• coalescing TB - central caseous necrosis

- Cavitation - results in greater viral load - risk of transmission

Question 15

Where does reactivation TB usually occur in the lung?

Answer 15

Apices of the lung (highest O2 tension - require O2 to survive)

Question 16

What is miliary TB?

Answer 16

widespread infection (primary or secondary with erosion of necrotic tubercle) - immunocompromised or young/old

Question 17

What characterises TB meningitis

Answer 17

Gradual onset

May lack constitutional ‘quartet’ e.g. fever, anorexia, weight loss, night sweats

Personality change

Question 18

What stain is used in TB Diagnosis?

Answer 18

Acid fast bacillus

Question 19

What is the standardised therapy for TB?

Answer 19

‘Directly observed therapy short’ (DOTS) - course

For pulmonary - 4 antibiotics (RIPS):
1st 2 months
RIFAMPICIN
ISONIAZID
PYRAZINAMID
STREPTOMYCIN

4 months
Rifampicin
Isoniazid

Question 20

What is the skin test that detects latent TB?

Answer 20

Mantoux test