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Flashcards in MTB Deck (28):
1

MTB - EPIDEMIOLOGY

Most common cause ID-related mortality in the worldPeak: 2003WHO aims to eliminate by 2015Humans: Only reservoirTransmitted: Person - to - person (aerosols)

2

Morphological & structural characteristics

Obligate aerobeBacillus, non-motileHeat sensitiveCatalase +Nitrate reductase, niacin, pyrazinamidase test Structural:Cell wall - pep layer, MYCOLIC ACID (long chain FAs, hydrophobic acids/waxes)

3

Media

MiddlebrooksLowenstein-jensen

4

Cord factor

combines w/mycolic acidcreates serpentine appearanceelicits granuloma formation

5

Catalase peroxidase

resists host cell's oxidative response

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Sulfatides

GlycolipidInhibits phagolysosome formationPromotes IC growth

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High mutation rate

requires multidrug therapy

8

Granuloma

macrophagesMGCfibroblastscollagen fibers

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active primary

1) when granuloma breaks loose & disseminates2) CASEOUS NECROSIS: internal lysis of macrophages/MTB cells in the granulomas3) FEVER4) radiography: hilar adenopathy, pulm infiltrates - looks like pneumonia5) droplet nuclei infects middle/lower lobes6) MTB gets phagocytosed by alveolar macro & multiplies....macro kills MTB and granuloma forms7) MTB dies, macro presents to TH1 cell. IFN-g released, activated macro.

10

active secondary

UPPER LOBESsuppression of T cells - insidious onset of diseasenormal symptoms + hemoptysis, dyspnea (SOB)

11

disseminated forms

ORAL MUCOSA: ulceration/paintongue & posterior mouth. osteomyelitis. salivary gland (parotid) infectionEYE: intraocular most common. anterior uveitis

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TST/Mantoux test

depends on 2 factors: size & risk of infection

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IGRA

measures TB sensitized t-cell IFN-G productionnot affected by BCG1 ov only, results in 24h

14

TX

3-4 drugs (ripe)rifampinisoniazidpyrazinamideethambutol

15

rifampin

RNA synthesis

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isoniazid

mycolic acid synthesis, hepatotoxic

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pyrazinamide/ethambutol

hepatotoxic

18

dots

most effective formdirectly observed treatment > short course

19

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

Mycobacterium kansasii(MAC-> #1)

20

MAC/MTB similarities

1. Both consists of SLOW-GROWING ORGANISMS 2. Strong ACID-FAST 3. AEROBIC BACILLI4. Gram- POSITIVE5. Grows on MIDDLEBROOK agar

21

MAC/MTB differences

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

22

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

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

23

MAC=

M. aviumM. intracellulareno person-to-personopportunistic

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MAC IN HIV (-)

PULMONARYfibrocavity disease (men): COPDfibronodulary disease (ladiez): BRONCHIECTASIS & lady windermere syndromelymphadenitis (kidsz): unilateral cervical nodes

25

MAC IN HIV (+)

PULMONARYnew infection, not latent reactivationlooks just like MTB, but GI componentDISSEMINATED (DMAC)lymphohematogenous dissemination of bactgranulomas NOT EFFECTIVEenlarged organs, organ dysfxncan't develop CMI (no macrophage activation or granuloma formation)

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>5mm

hiv + ptsimmunosuppresedrecnt contact w/TB ptsabnormal chest radiographs

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>10mm

immigrantsdrug usershealthcare employeeskids <4 exposed

28

>15mm

positive