19 - Mycobacterial diseases Flashcards

1
Q

Mycobacteria are

A

slender bacillus

different: unusual waxy cell wall with high lipid content and slow growing and different media req.

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2
Q

Mycobacteria and gram staining

A

poor uptake

gram +ve: ghost cells

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3
Q

Retain certain stainds without decolourisation

A

Acid fast bacilli (AFBs)

Ziehl Neelsen, phenol auramine stains

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4
Q

Diseases caused by mycobacterium

A

TB - M.TB, M.bovis
Leprosy - M.leprae
Atypical mycobacteria = M.avium complex, M.kansasii, M.marinum (fish tank granuloma)

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5
Q

M. TB

A

Global emergency
1/3 infected
2million deaths pa
Mainly affects Africans

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6
Q

M.TB - pathogenesis

A

Inhalation of infected resp. droplets

Usually pulm.disease (>50% of cases)

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7
Q

M.TB - 1° TB

A

1° acquisition
periphery of lung midzone most common site
inhaled bacilli phagocytosed by macrophages
hilar lymph nodes - “Ghon focus”
Intracellular multiplication

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8
Q

M.TB - body’s response

A

Granuloma
Cell-mediated immune response
Central area of epithelioid cells, giant cells
Surrounding lymphocytic cell infiltration
Central area caseous necrosis
Fibrosis/calcification of lesions
Bacilli slowly die / remain viable for 20 years

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9
Q

M.TB - clinical presentation

A

influenza-like
CXR
TB skin test conversion

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10
Q

reactivation TB

A
lowered immunity >50yo
malnutrition
-OHism
debilitating illness
HIV
Silicosis, chronic renal failure, gastrectomy

Anti-TNFa blockade e.g. infliximab

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11
Q

reactivation TB - clinical presentation

A

coalescing tubercles, central caseous necrosis

cavitation with high organism load

lung apices have highest oxygen tension

chronic productive cough w/ haemotypsis
weight loss, fever, night sweats

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12
Q

Extra-pulmonary

A

disseminated (miliary TB)

very young/old; immunocompromised

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13
Q

TB meningitis - clinical presentation

A
Often insidious onset
unidentified fever
personality change
focal neuro deficit: basilar inflammation
mild headache / meningism

may lack constitutional quartet

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14
Q

constitutional quartet

A

fever, night sweats, anorexia, weight loss

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15
Q

TB - diagnosis

A
clinical
CXR
Histology
skin testing
blood testing - IFN-y

Microbiology

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16
Q

Positive AFB culture would prompt

A

referral to regional reference lab
species indication
sensitivities within two weeks
strain typing

17
Q

Leprosy aka

A

Hansen’s disease

18
Q

Leprosy - clinical forms

A

Tuberculoid - macules/plaques
Nerve: ulnar, common peroneal

Lepromatous: subcut tissue accumulation; ear lobes, face

19
Q

Leprosy - treatment

A

Dapsone, rifampicin, clofazimine