MTB

Question 1

MTB - EPIDEMIOLOGY

Answer 1

Most common cause ID-related mortality in the world
Peak: 2003
WHO aims to eliminate by 2015

Humans: Only reservoir
Transmitted: Person - to - person (aerosols)

Question 2

Morphological & structural characteristics

Answer 2

Obligate aerobe
Bacillus, non-motile
Heat sensitive
Catalase +
Nitrate reductase, niacin, pyrazinamidase test 

Structural:
Cell wall - pep layer, MYCOLIC ACID (long chain FAs, hydrophobic acids/waxes)

Question 3

Media

Answer 3

Middlebrooks

Lowenstein-jensen

Question 4

Cord factor

Answer 4

combines w/mycolic acid
creates serpentine appearance
elicits granuloma formation

Question 5

Catalase peroxidase

Answer 5

resists host cell’s oxidative response

Question 6

Sulfatides

Answer 6

Glycolipid
Inhibits phagolysosome formation
Promotes IC growth

Question 7

High mutation rate

Answer 7

requires multidrug therapy

Question 8

Granuloma

Answer 8

macrophages
MGC
fibroblasts
collagen fibers

Question 9

active primary

Answer 9

1) when granuloma breaks loose & disseminates
2) CASEOUS NECROSIS: internal lysis of macrophages/MTB cells in the granulomas
3) FEVER
4) radiography: hilar adenopathy, pulm infiltrates - looks like pneumonia
5) droplet nuclei infects middle/lower lobes
6) MTB gets phagocytosed by alveolar macro & multiplies….macro kills MTB and granuloma forms
7) MTB dies, macro presents to TH1 cell. IFN-g released, activated macro.

Question 10

active secondary

Answer 10

UPPER LOBES
suppression of T cells - insidious onset of disease
normal symptoms + hemoptysis, dyspnea (SOB)

Question 11

disseminated forms

Answer 11

ORAL MUCOSA: ulceration/pain
tongue & posterior mouth. osteomyelitis. salivary gland (parotid) infection

EYE: intraocular most common. anterior uveitis

Question 12

TST/Mantoux test

Answer 12

depends on 2 factors: size & risk of infection

Question 13

IGRA

Answer 13

measures TB sensitized t-cell IFN-G production
not affected by BCG
1 ov only, results in 24h

Question 14

TX

Answer 14

3-4 drugs (ripe)
rifampin
isoniazid
pyrazinamide
ethambutol

Question 15

rifampin

Answer 15

RNA synthesis

Question 16

isoniazid

Answer 16

mycolic acid synthesis, hepatotoxic

Question 17

pyrazinamide/ethambutol

Answer 17

hepatotoxic

Question 18

dots

Answer 18

most effective form

directly observed treatment > short course

Question 19

What species of Mycobacterium is the second leading cause of NTM infection in HIV-infected patients

Answer 19

Mycobacterium kansasii

MAC-> #1

Question 20

MAC/MTB similarities

Answer 20

1. Both consists of SLOW-GROWING ORGANISMS
2. Strong ACID-FAST
3. AEROBIC BACILLI
4. Gram- POSITIVE
5. Grows on MIDDLEBROOK agar

Question 21

MAC/MTB differences

Answer 21

1. Reservoirs
   a. MAC → soil & water
   b. MTB → Humans
2. MAC colonies
   a. NO CORDING or CLUSTERING
   b. Small, flat, translucent, smooth colony
   c. Occasionally pale yellow pigment
   d. LACK of GRANULOMA FORMATION
   e. OVERGROWTH of microbe

Question 22

treatment of MAC in HIV (-) vs HIV (+) pts

Answer 22

antibiotics for both (clarithromycin, azithromycin, ethambutol, rifampin)

(+): HAART

(+) W/MAC: lifelong antiretroviral; or antiretroviral for 2 wks then HAART (don’t begin both = IRIS…immune reconstitution inflamm syndrome)

(+) W/NO MAC: chemoprophylaxis until CD4TCELL>100cell/uL

(-): antibiotics until sputum is neg for a year

Question 23

MAC=

Answer 23

M. avium
M. intracellulare

no person-to-person
opportunistic

Question 24

MAC IN HIV (-)

Answer 24

PULMONARY
fibrocavity disease (men): COPD
fibronodulary disease (ladiez): BRONCHIECTASIS & lady windermere syndrome
lymphadenitis (kidsz): unilateral cervical nodes

Question 25

MAC IN HIV (+)

Answer 25

PULMONARY
new infection, not latent reactivation
looks just like MTB, but GI component

DISSEMINATED (DMAC)
lymphohematogenous dissemination of bact
granulomas NOT EFFECTIVE
enlarged organs, organ dysfxn
can't develop CMI (no macrophage activation or granuloma formation)

Question 26

> 5mm

Answer 26

hiv + pts
immunosuppresed
recnt contact w/TB pts
abnormal chest radiographs

Question 27

> 10mm

Answer 27

immigrants
drug users
healthcare employees
kids <4 exposed

Question 28

> 15mm

Answer 28

positive