TB

Question 1

Type of lesions in TB

Answer 1

Caseating granulomas

Question 2

Microbiology of TB

Answer 2

• Non-motile rod-shaped bacteria (structurally gram +ve)

Acid-alcohol fast bacilli (AAFBs)

Question 3

What staining do you use to identify TB

Answer 3

o Ziehl-Neelsen = diagnosis

Question 4

What are Non-tuberculous Mycobacterium?

Answer 4

o Ubiquitous
o Environmental (i.e. water and soils)
o Atypical

Question 5

What features do NTB have

Answer 5

o Spectrum of pathogenicity (majority are not pathogenic to humans) and may be found colonising (not infecting)
o Not transmitted person-to-person
o Commonly resistant to the usual anti-TB therapy

Question 6

Types of slow growing NTM and what they cause

Answer 6

M avian intracellulae-
Immunocompetent - invade bronchial tree Immunosuppressed - disseminated infection

o Mycobacterium marinum:
Swimming pool granuloma

o	Mycobacterium ulcerans:
Skin lesions (e.g. Bairnsdale ulcer, Buruli ulcer)

Question 7

Types of NTM and what they cause

Answer 7

 Mycobacterium abscessus
 Mycobacterium chelonae
 Mycobacterium fortuitum

o Causes skin and soft tissue infections:
 Tattoo-associated outbreaks
 Hospital settings from blood cultures

Question 8

Treatment of NTM

Answer 8

o Mycobacterium avium intracellulare / Slow-growing NTM:
RICES

 Rifampicin
 Clarithromycin/azithromycin
 Ethambutol
 ± streptomycin/amikacin

o Rapid-growing NTM:
 Based on susceptibility testing
 Usually macrolide based

Question 9

What are the two types of Mycobacterium leprae, their symptoms and their T cell response?

Answer 9

• Paucibacillary tuberculoid
o Few skin lesions + less joint infiltration
o Robust T cell response

• Multibacillary lepromatous
o Abundance of bacilli
o Multiple skin lesions + joint infiltration
o Poor T cell response

Question 10

What is the natural history of TB

Answer 10

o	Primary TB:
	Usually asymptomatic 	
Ghon focus (granuloma in the lungs) 
	Controlled by cell-mediated immunity	Rare allergic reactions include erythema nodosum
	Occasionally  disseminated/miliary TB

o Latent TB
o Reactivation of TB

Question 11

What is post-primary TB and how long does it take to happen

Answer 11

Reactivation or exogenous re-infection:

o Happens >5 years after initial infection

Question 12

What TB manifestations does the immune response have a less effective response, in order?

Answer 12

Least- milliary, meningeal, pulmonary, localised extra pulmonary

Question 13

Findings of pulmonary TB

Answer 13

o Causes caseating granulomata:
 Lung parenchyma
 Mediastinal lymph nodes
o Commonly found in the upper lobes

Question 14

Examples of extrapulmonary TB

Answer 14

Lymphadenitis
GI- may present like IBD
Bone- Potts disease
Milliary- to haematogenous disease 
Meningitis

Question 15

How the mantoux test works

Answer 15

Inject intradermally with tuberucllin

If previous infection- mount response by delayed type IV hypersensitivity reaction

Question 16

Treatment of TB

Answer 16

o R Rifampicin 6m
o I Isoniazid 6m
o P Pyrazinamide 2m
o E Ethambutol 2m

o CNS TB needs 10 months
o Cure rate 90%

Question 17

Side effects of RIPE treatment

Answer 17

o Rifampicin:
 Orange secretions
 Raised transaminases (ALT/AST)
 Induces CYP450

o Isoniazid: Other Treatments:
 Peripheral neuropathy (give with pyridoxine)
 Hepatotoxicity (DILI)

o Pyrazinamide:
 Hepatotoxicity (DILI)

o Ethambutol:
DILI = Drug-Induced Liver Injury
 Visual disturbance

Question 18

Types of resistances of TB

Answer 18

o Multi-Drug Resistant (MDR)  resistant to rifampicin and isoniazid

o Extremely Drug Resistant (XDR)  resistant to rifampicin, isoniazid, fluoroquinolones and at least 1 injectable

Question 19

Treatment of resistant TB

Answer 19

o Quinolones + aminoglycosides + para-aminosalicylic acid (PAS) + cycloserine + ethionamide