mycobacteria Flashcards
why dont mycobacteria gram stain well ?
due to the presence of mycolic acid in the cell wall
what stain is used for mycobacteria ?
ziehl neelsen
what is the most common non TB mycobacterial infections ?
MAC
what is the classic patient associated with MAC and what are the associated findings ?
usually associated with HIV/AIDS patients
very low CD4 count less than 50
fever sweats w keda
severe anemia
hepatosplenomegaly
inc ALP inc LDH
often no lung findings on chest x ray
how is a diagnosis of MAC made ?
blood culture but very slow
what is the treatment and prophylaxis of MAC ?
treatment is clarithromycin and ethambutol
prophylaxis: azithromycin
what is the cause of leprosy and what is the other name for this disease ?
mycobacterium leprae
also called hansens disease
what is the reservoir for leprosy ?
armadillos
what are the most ideal growing environments for leprosy ?
they cannot be cultured and grow best on cold surfaces so they grow on the face and hands
what type of inflammation is associated with leprosy ?
granulomatous inflammation
what are the symptoms of leprosy ?
infects the skin and superficial nerves
associated with skin lesions and loss of sensation
what is the severity of the spectrum of the disease of leprosy dependant on ?
depends on the cell mediated response
what are the two types of leprosy ?
tuberculoid leprosy - milder disease patches of hypopigmented skin
lepromatous leprosy - severe disease diffuse hypopigmentation with hair loss
what causes tuberculoid leprosy vs lepromatous leprosy ?
tuberculoid leprosy - strong cell mediated Th1 response , lesion shows mgranulomas but few bacteria
lepromatous leprosy - mediated by a Th2 response associated with multiple bacteria and few granuloma
how is the diagnosis of leprosy made ?
CANNOT BE CULTURED
acid fast organisms on skin biopsy
what test can give a false positive for leprosy ?
VRDL
what is the treatment for leprosy ?
tuberculoid - dapsone and rifampcin
lepromatous - dapsone , rifampcin and clofazimine
what is the mechanism of each of these drugs :
Rifampin
Dapsone
Clofazimine
Rifampin - blocks RNA synthesis
Dapsone - competes with PABA
Clofazimine - disrupts the DNA
what are the diseases that need dapsone ?
leprosy
pneumocystis jirovecii
why must dapsone be avoided in G6PD ?
may trigger hemolysis
what drug works similarly to dapsone ?
sulfonamide
what is the function of IL-12 ?
triggers the differentiation T cells to Th1 cells
Th1 cells produce IFN gamma
what does IL12 receptor deficiency result in ?
disseminated salmonella
disseminated NTM
disseminated BCG after vaccine
what is the treatment of IL 12 receptor deficiency ?
IFN gamma
for what type of response is IL 12 important for ?
important for intracellular infections
what type of mycobacterium is associated with cervical lymphadenitis in children ?
mycobacterium scrofulaceum
what type of mycobacterium is associated with aquarium handlers ?
mycobacterium marinum
what are the virulence factors associated with mycobacterium tuberculosis ?
cord factor - serpentine cord which activated=s macrophages and allows for the formation of granuloma and induces the release TNF alpha
sulfatides- inhibits phagolysosomal fusion
what test is associated with less false positives when it comes to testing for TB ?
IGRA assay
PPD has more false negatives
what is histologically characteristic of secondary tuberculosis ?
caseating granuloma with central necrosis and langhans giant cell
where is reactivation of TB most likely to happen and what type of patient is more associated with reactivation ?
in the apices of the lung because the bacteria is highly aerobic
more common in immunocompromised patients
what is the distribution of neuropathy in leprosy ?
glove and sock neuropathy
