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medical micro > TB, fungal and parasitic infections > Flashcards

TB, fungal and parasitic infections Flashcards

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USMLE® Step 1 flashcards
1
Q

TB symptoms

A

Persistent cough (>3 weeks), phlegm and blood
Fever
Loss of energy
Night sweats

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2
Q

TB transmission

A

Survive in air and dust for long periods

droplet nuclei are inhaled, enter the lungs and travel to the alveoli

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3
Q

What is feature of M. tuberculosis that makes it successful

A

Lipid rich cell walls, which is resistant to disinfectants, detergents, antibiotics and many host immune responses

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4
Q

What type of cells does M. tuberculosis infect

A

Alveolar macrophages, grows intracellularly.

Prevents fusion of lysosome and phagosome

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5
Q

Pathogenesis of TB

A

Stimulates a strong cell mediated immune response as macrophages release cytokines.

Macrophages ingest and surround the bacilli and form a granuloma (dormant). If the immune system fails, may spread by the lymphatic system to more distant tissues and organs.

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6
Q

Latent TB

A

Not infectious

granuloma

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7
Q

Infectious TB

A

Reactivation: If the immune system fails, the bacilli multiply rapidly in the lungs, kidneys, brain or bone.

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8
Q

Secondary TB

A

Bacteria can remain dormant and activate weeks, months or years later. More server symptoms: violent coughing, bloody sputum, weight loss and extreme fatigue. Gradual wasting of the body.

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9
Q

What happens to the lungs in chronic TB

A

Tubercles filled with bacteria expand and cause cavities in the lungs

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10
Q

What is extrapulmonary TB

A

Infection outside the lungs

Regional lymph nodes, kidneys, bones, brain and meninges

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11
Q

Tubercular meningitis

A

Brain leisons lead to mental retardation, blindness and deafness

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12
Q

Outcome of neurological damage in TB

A

extensive paralysis and sensory loss

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13
Q

Tuberculin skin test (Mantoux test)

A

intradermal injection into forearm of purified protein derivative (PPD)
Solution is derived from culture of M. tuberculosis

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14
Q

Tuberculin skin test (Mantoux test) results

A

after 48-72 hours
Site is observed for a red wheal (induration)
Measured and interpreted as positive and negative according to size and patient category

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15
Q

Tuberculin skin test Patient Category 1

A

lump: 5-9mm
Contact with actively infected TB patients
HIV positive or have risk factors for HIV infection
Past history of TB determined by chest X-rays

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16
Q

Tuberculin skin test Patient Category 2

A

lump: 10-14mm
HIV negative IV drug user
Live or work in high risk residences e.g. jails
New immigrants from countries with high rates of TB
Low-income populations lacking adequate medical care

17
Q

Tuberculin skin test Patient Category 3

A

lump: 15mm

Patients who do not meet criteria in categories 1 or 2

18
Q

Diagnosis of latent TB

A

TB skin test or TB blood test: positive
Chest X-Ray: normal
Sputum smears and cultures: negative

19
Q

Diagnosis of reactivated TB

A

Chest X-ray: cavitation

Sputum smears and cultures: positive

20
Q

Diagnosis of active TB

A

Acid-Fast staining of sputum (takes an hour)
Ziehl-Neelsen stain
Bacilli: bright red
Backgroung: blue

21
Q

TB treatment

A

6 month course of first line drugs

isoniazid, rifampicin, ethambutol

22
Q

MDR-TB treatment

A

Does not respond to isoniazid and rifampicin

second line drugs (limited chemotherapy up to 2 years-TOXIC)

23
Q

XDR-TB treatment

A

No treatment

24
Q

TB vaccine

A

BCG
live attenuated
not effective in preventing disease or reactivation among those already infected

25
Q

What is Aspergillus

A

Most abundant fungi genus in the world

26
Q

Aspergillus ecological niche

A

soil, air and decaying matter

hospitals: ventilation systems, showerheads

27
Q

How does Aspergillus reproduce

A

Both sexual and asexual

28
Q

Aspergillus spores

A

green pigmented asexual conidia (long chains radiating)

29
Q

Aspergillus transmission

A

Sporulate and release airborne conidia
Inhalation of airborne conidia (not transmitted person to person)
These are small and can reach pulmonary alveoli

30
Q

Aspergillus infection in health people

A

Conidia are engulfed by alveolar macrophages and phagocyted

31
Q

Aspergillus infection in immunocompromised individuals

A

Incomplete killing of conidia

Results in germination and tissue invasion

32
Q

Aspergillosis

A

Broad spectrum of disease caused by members of the genus Aspergillus

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