TB Flashcards
strongest risk factor for TB
HIV- more progression from recent infection or latent infection to disease
4 first line TB drugs
isoniazid (INH), Rifampicin (RIF), Pyrazinamide (PZA), Ethambutol (ETH)
define MDR TB
resistant to INH and RIF
define XDR TB
resistant to 2 classes of second line drugs as well
what is DOTS
directly observed treatment short course- medical providers observe pts taking meds to improve compliance
what is BCG
live attenuated vaccine w/ mycobacterium bovis, variable effeciency and not used in the US
how to prove an organism causes disease?
Koch’s postulates:
- isolate bacilli
- grow in culture
- administer isolates into animals
- re-isolate bacilli
what type of organism is TB?
mycobacterium, facultative intracellular, acid fast
typical cellular location of TB
macrophages
2 kinds of acid fast stains
zeihl-neelsen, fluorescent auramine-rhodamine
how is myobacteria different
mycolic acid in the cell wall, no LPS
cannot be gram stained
transmission of TB
via aerosols and airborne droplets, grows in macrophages
list some characteristics of airborne precautions and 2 organisms they are for
w/ TB and measles
- private room w/ neg pressure
- N95 masks for providers
- visitors have surgical masks
mechanism for TB resistance to macrophage killing
can resist ROI and RNI; arrests phagosome maturation at early endosome stage and binding w/ lysososme
what type of immune response is needed for TB control? How?
Th1 response to macrophage (and dendritic cells) MHC molecules, release of IFN-gamma to activate macrophages and help them destroy TB (via radicals and lysosome fusion)
role of antibodies in Mtb control
none, control by CD4 and CD8
TNF alpa role in TB
responsible for disease Sx like weight loss and fever, helps IFN gamma activate macrophages
IL 12 role in TB
CD4 differentiation into Th1
CD4 role in TB
make IFN gamma
CD8 role in TB
can also produce IFN gamma or directly kill infected macrophages, releasing the contents for further phagocytosis by other cells
positive PPD
certain amount of hardened tissue (induration) indicating the presence of antibodies to TB and at least a latent infection
describe a granuloma
organized structure w/ central region of macrophages and giant cells, surrounded by lymphoid cells and other new macrophages
-can have necrotic center
what is a tubercle
a granuloma walled off by a fibrin coat, can calcify and be visible on xray
what happens in center of granuloma
becomes necrotic and liquid, site for extracellular replication
6 Sx of active Tb
chronic cough, hemoptysis, chest pain, weight loss, fever, night sweats
cause of Tb sx
immune response: cytokines like IL1 and TNFalpha, macrophages, cytolytic T cells
difference in primary Tb w/ HIV for pathogenesis
no containment, allows for dissemination and miliary TB
PPD test w/ HIV pts
doesnt always work- test depends on functioning lymphocytes
PPD test w/ BCG vaccine
can cause cross rxn and false positive
fn of quantiferon test
measures IFN gamma from T cells in response to TB antigens not in BCG, positive depending on the response
fn of new Xpert MTB/RIF test
PCR test for Mtb, also determine rifampicin resistance, recommended for those who have HIV coinfection
differentiate 2 forms of leprosy
tubercuoloid: driven by Th1 response, deformities due to nerve damage (able to contain granulomas)
lepromatous leprosy: active, nodulous from Th2 response that does not fully contain bacteria
common sites of Non-TB mycobacteria (NTM)
southern and midwestern US- but normal inhabitants of soil and water
myco avium location and transmission
found in water supplies, forms biofilms, transmitted by inhalation/ingestion, more common in HIV
myco abscessus location and transmission and infection
common in soil and water, common in bronchiectasis/CF pts, forms biofilms
chronic lung infection, skin/soft tissue infections, highly resistant to drugs
association w/ myco fortuitum
fast growing NTM, found in nail salons
