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Respiratory > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

Common causative organisms of tuberculosis

A

Mycobacterium tuberculosis or Mycobacterium bovis

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2
Q

Pathology of TB

A

Primary TB - Inhaled organism is phagocytosed and carried to hilar lymph nodes. Immune activation leads to granulomatous response in nodes usually killing of organism.
Secondary TB - Reactivation of disease which tends to remain localised often in apices of lungs. Can spread via airways or bloodstream

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3
Q

Time period of primary TB

A

1st exposure and upto 5 years afterwards

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4
Q

Tissue changes in TB

A

Primary - Ghon focus (small lesion in pleural cavity) in periphery of mid zone of lungs. Large hilar nodes (granulomatous)
Secondary - Fibrosing and cavitating apical lesion with caseous necrosis

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5
Q

What is a ghon focus

A

A small lesion in pleural space caused by Mycobacterium tuberculosis. It is a granulomatous inflammation.

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6
Q

What stain is used to identify TB causing organism

A

ZIehl-Neelsen stain

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7
Q

What can secondary TB lead to

A

Miliary TB which is widespread dissemination of Mycobacterium tuberculosis via hematogenous (via blood) spread. It involves millet like seeding of TB bacilli in lungs.

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8
Q

Why does TB get reactivated

A

Decrease T cell function due to -
Age, immunosuppression (steroids, cancer, chemotherapy), immunodeficient (HIV)
Reinfection at high dose or more virulent organism

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9
Q

What is bronchoalveolar lavage (BAL)

A

A medical procedure in which a bronchoscope is inserted through the mouth or nose into lungs and fluid is squirted into a small part of the lungs. This is examined and useful in diagnosing lung disease

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10
Q

What causes pneumocystis pneumonia (PCP)

A

Caused by yeast-like fungus called Pneumocystis jirovecii. Found in immunocompromsied hosts

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11
Q

A young African man presents with a cough and night sweats. His chest x-ray shows dense consolidation in the right upper lobe with cavity formation.

A

This is Tuberculosis

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12
Q

How does Mycobacterium tuberculosis spread

A

Air

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13
Q

What happens after exposure to TB

A

Mycoplasma tuberculosis infects phagoctyes such as macrophages and neutrophils. Granulomas are formed to wall off the pathogen. However this can be a growing collection of cells for the pathogen to infect and replicate within. Most time the granulomas sustain and the infection is dealt with. However, it may burst causing the pathogen to travel around

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14
Q

Clinical features of TB

A

Weight loss, malaise, night sweats, cough, haemoptysis, breathlessness, upper zone crackles

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15
Q

What are cold abscess

A

Collection of pus without the pain and acute inflammation seen in conventional abscess

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16
Q

Why should steroids not be injected into solitary arthritic joint

A

It might be tuberculosis

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17
Q

What stain is used in TB

A

Ziehl-Neelsen stain

18
Q

How long is TB sputum sample cultured for

A

12 weeks as this might pick up additional culture positive cases who will need treatment but not infectious due to tiny number of pathogens

19
Q

What does positive PCR for TB indicate

A

Patient may have had the disease previously

20
Q

What cells are seen under microscope in TB

A

Multinucleate giant cells - Mass formed by union of several distinct cells (cells of macrophage lineage fused together). Often form a granuloma

21
Q

How does TB heal

A

With calcification, often leave scar tissue

22
Q

Where does TB usually affect lungs

A

Upper lobe predominance. Lung cancer/pneumonia often affects middle/lower lobe

23
Q

TB that resembles the appearance of millet seeds

A

Miliary TB, massive seeding of TB through the bloodstream which can lead to rapid fatality

24
Q

Therapy for TB

A

2 months of -
Rifampicin, Isoniazid, Pyrazinamide, Ethambutol
Then 4 months of -
Rifampicin, Isoniazid

25
Q

What TB drug can affect hormonal contraception

A

Rifampicin

26
Q

Rifampicin side-effects

A

Discolours urine and bodily fluids orange

27
Q

Ethambutol side-effects

A

Optic neuritis

28
Q

Types of TB drug resistance

A 
Multi-drug resistance (MDR) - 
Rifampicin and Isoniazid 
Extensive drug resistance (XDR) - 
MDR + quinolone and injectable
Usually seen in russian states
29
Q

What test should always be done for TB

A

HIV as it might be a co-infection

30
Q

How does latent TB show on x-rays

A

No symptoms however there may be granulomas or calcification left over.

31
Q

Tests for previous exposure to TB antigen

A

Blood - Interferon gamma release assay (IGRA)

Skin - Mantoux (tuberculin) test

32
Q

Drawback of mantoux test

A

Cannot distinguish between latent, cured, active TB and BCG

33
Q

Why does mantoux test involve 48 hours wait

A

Reaction to Mycobacterium is a type 4 hypersensitivity (delayed) reaction. Hence, we wait and see

34
Q

What is Mantoux test also known as

A

Tuberculin Skin Test (TST)

35
Q

Drawbacks of tuberculin skin test (TST)

A

Operator dependant and low sensitivity. Reaction is also diminished in immunocompromised individuals

36
Q

Management of latent TB

A

Best left alone however can give drugs -
6 months of Isoniazid or
3 months of Rifampicin and Isoniazid combination

37
Q

6 months Isoniazid vs 3 months Rifampicin + Isoniazid

A

6 months is with one drug but longer whereas 3 months involves two drug; more side-effects

38
Q

What should be screened for before starting anti-TNF drugs

A

TB as anti-TNF drugs can reactivate TB

39
Q

How is BCG related to TB

A

BCG is an attenuated strain of Mycobaterium bovis

40
Q

How can TB be prevented

A

Contact tracing to identify cases, screening of high risk subgroups, isolate infectious cases, BCG immunisation, social measures

41
Q

HIV and TB

A

All TB cases should be offered an HIV test

All HIV cases should be offered a chest x-ray

42
Q

Steroids and TB

A

Steroids and other immunosuppresant drugs can reactivate TB

Respiratory (26 decks)

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