Tuberculosis

Question 1

Describe M. Tuberculosis

Answer 1

Non-motile bacillus w/ slow growth time that lacks pigment

Question 2

How is M. Tuberculosis transmitted?

Answer 2

Respiratory Droplets; NOT CONTACT

Question 3

Pathogenesis of M. Tuberculosis

Answer 3

1. Inhaled organism deposits in Lower lobes (greatest airflow)
2. Macrophages ingest organims, then travel to hilar/mediastinal lymph nodes
3. Lymphatic and Hematogenous dissemination
4. Positive PPD 6-14 wks after infection

Question 4

When is there extrapulmonary dissemination? Where will you find secondary pulmonary infections?

Answer 4

HIV pts with <200 T cells

Apical posterior lung (High O2)

Question 5

In what situation is their caseous necrosis?

Answer 5

High Ag load and tissue hypersenstivity

Question 6

How do you interpret the Mantoux skin test?

Answer 6

1. Read 48-72 hrs after application
2. Measure the area of induration
3. A positive test DOES NOT imply infection, only exposure

Question 7

Describe a postive mantoux skin test

Answer 7

> 5mm + in: close contacts, HIV+, CXR w/ fibrosis
10mm + in: medical conditions, foreign-born from high-prevalence areas, low-income populations, high-risk minorities, IVDU, long-term care facility residents
10mm is generally considered + in anybody

Question 8

How is TB diagnosed?

Answer 8

Bacterial culture confirms diagnosis
also
3 sputum specimens should be examined.

Question 9

Distinguish Primary infection from chronic pulmonary TB

Answer 9

Primary: Gohn node, non-specific infiltrate
Chronic: Apical posterior upper lobes, fibrous scar

Question 10

Discuss Cavitary Disease

Answer 10

Large # organisms, highly infectious, dissemination
Superinfection: Aspergillus, atypical mycobacteria
Underlying carcinoma if doesn’t respond to Tx

Question 11

What are the 2 principles of TB tx?

Answer 11

1. Treat for longer periods (b/c slow growing)

2. Use 2 drugs (begin Tx w/ 4 drugs until you get culture ID results)

Question 12

Tx in pregnant pts

Answer 12

1. TB poses a risk to the fetus so begin Tx w/ INH/RIF/EMB

2. Streptomycin is TERATOGENIC

Question 13

Isoniazid

Answer 13

1. Inhibits mycolic acid synthesis
2. Hepatotoxic; MUST CHECK LFTs, peripheral neuropathy, SJS, SLE
3. Interacts with cheese and wine

Question 14

RIfampin

Answer 14

1. Inhibits RNA synthesis
2. Orange secretion, hepatitis
3. Interacts with warfarin and quinidine

Question 15

Pyrazinamide

Answer 15

1. Effective against dormant cells w/in macrophages
2. prodrug activated by bacteria
   3, Fever, polyarthralgia, photosensitivity

Question 16

Ethambutol

Answer 16

1. Inhibits arabinoyl transferases
2. Optic neuritis
3. MONITOR VISUAL ACUITY

Question 17

Streptomycin or Amikacin

Answer 17

2nd line Tx
Inhibit protein synthesis @ 30S ribosome
Renal toxicity