Tuberculosis Flashcards
classification of mycobacteria
M. leprae- leprosy (Hansens Disease)
M. tuberculosis
non-tuberculosis mycobacteria (NTM)
mycobacterium gram stain and morphology
weakly positive rods
mycobacterium motility
non motile
mycobacterium spores
non spore forming
mycobacterium capsule
no capsule
mycobacterium cell walls
contain fatty acids- absent in most other
mycobacterium acid fastness
stain with ziehl neelsen procedure, making them appear red
TB transmissoin
person to person by inhalation
ingested by alveolar macrophages and induce granuloma formation in the lung (rarely brain liver or kidney)
may cause transient bacteremia
may stay latent for years before transitioning to a TB disease
TB syndromes
ghon lesion, ghon complex, and ranke complex- seen on imaging
cavitary TB- hole in the lung from TB damage, containing large number of bacteria
miliary TB- occurs throughout the entire lung and potentially whole body
extrapulminary TB- miliary, lymphatic, skeletal, or any non lung site
TB and HIV`
leading opportunistic infection of HIV infected pts b/c it is CD4 cell mediated immunity that is compromised in HIV
diagnosing active TB
acid fast bacillus smear- same day results but limited sensitivity and specificity
culture- takes more time but more sensitive
nucleic acid ampliciation- fast
TB treatment
isonizaid- cidal for extracellular, causes hepatitis and neuropathy
rifampin- cidal for intracellular, causes hepatitis and influenza syndrome
pyrazinamide- intracellular, causes GI, hepatitis, and rash
ethambutol- static, causes optic neuritis, rash
RIPE for 2 months, then INH/rifampin for 4 months
multidrug resistance to TB
resistance to INH and rifampin
treatment is expensive and takes years
diagnosis of latent TB
PPD- delayed hypersensitivity test
TB contact or HIV- greater than 5
for immigrant, drug user, hospital worker, or diabetic- greater than 10
for persons w/o risk- greater than 15
IGRAs
interferon gamma release assats- blood assay for TB
mononuclear cells from pts w/ TB infection and normal T cell immunity prouce IFN in response to TB Ags
treatment for latent TB
INH for 9 months
rifampin for 4 months
mycobacterium bovis
related to TB, causes TBs in cows and milk can cause GI “TB” in humans- attenuated strain is source of vaccine for TB
works well in children
can cause positive PPD tests
mycobacterium leprae is special because…
cannot be cultivated in vitro
obligate intracellular
mycobacterium leprae pathophysiology
likes cooler temps- skin, nose, upper respiratory tract
armidillos are other host
respiratory transmission
incubation period is 2-5 years
differences between TB and leprosy
TB- granulomas, few bacteria, cellular immune rxn, lepromin skin test positive, good prognosis
lepsory- few granulomas, many bacteria, nodules and diffuse thickening, Ab immune rxn, negative lepromin skin test, poor prognosis
leprosy diagnsosi
appearance of lesions and acid fast stains
treatment of leprosy
chemotherapy- dapsone, rifampin, clofazimine
nonTB mycobacteria transmission
not human to human
found in soil, water, animals
runyon classification
classification of nonTB mycobacteria based off how fast they grow and whether they express color in light or dark
mycobacterium avium
most common NTM in US
found in water soil and birds
mycobacterium avium syndromes
cervical adenitis in children
pulmonary disease in pts w/ chorninc lung disease
pulmonary disease in normal hosts
disseminated infection in AIDS
treatment takes 18 months
