MTB Flashcards
MTB - EPIDEMIOLOGY
Most common cause ID-related mortality in the worldPeak: 2003WHO aims to eliminate by 2015Humans: Only reservoirTransmitted: Person - to - person (aerosols)
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)
Media
MiddlebrooksLowenstein-jensen
Cord factor
combines w/mycolic acidcreates serpentine appearanceelicits granuloma formation
Catalase peroxidase
resists host cell’s oxidative response
Sulfatides
GlycolipidInhibits phagolysosome formationPromotes IC growth
High mutation rate
requires multidrug therapy
Granuloma
macrophagesMGCfibroblastscollagen fibers
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.
active secondary
UPPER LOBESsuppression of T cells - insidious onset of diseasenormal symptoms + hemoptysis, dyspnea (SOB)
disseminated forms
ORAL MUCOSA: ulceration/paintongue & posterior mouth. osteomyelitis. salivary gland (parotid) infectionEYE: intraocular most common. anterior uveitis
TST/Mantoux test
depends on 2 factors: size & risk of infection
IGRA
measures TB sensitized t-cell IFN-G productionnot affected by BCG1 ov only, results in 24h
TX
3-4 drugs (ripe)rifampinisoniazidpyrazinamideethambutol
rifampin
RNA synthesis
isoniazid
mycolic acid synthesis, hepatotoxic
pyrazinamide/ethambutol
hepatotoxic
dots
most effective formdirectly observed treatment > short course
What species of Mycobacterium is the second leading cause of NTM infection in HIV-infected patients
Mycobacterium kansasii(MAC-> #1)
MAC/MTB similarities
- Both consists of SLOW-GROWING ORGANISMS 2. Strong ACID-FAST 3. AEROBIC BACILLI4. Gram- POSITIVE5. Grows on MIDDLEBROOK agar
MAC/MTB differences
- 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
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
MAC=
M. aviumM. intracellulareno person-to-personopportunistic
MAC IN HIV (-)
PULMONARYfibrocavity disease (men): COPDfibronodulary disease (ladiez): BRONCHIECTASIS & lady windermere syndromelymphadenitis (kidsz): unilateral cervical nodes
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)
> 5mm
hiv + ptsimmunosuppresedrecnt contact w/TB ptsabnormal chest radiographs
> 10mm
immigrantsdrug usershealthcare employeeskids <4 exposed
> 15mm
positive
