1-27 Mycobacteria Flashcards
eradication of TB seemed possible until
AIDS
describe the implications of mycobacteria’s slow growth
delays in vitro culture, defeats some antibiotics that target rapidly growing cells
gram stain of mycobacteria?
poorly due to mycolic acid cell wall structure (fatty)
how do you stain mycobacteria?
acid-fast.
gram + are acid fast -, myocbacteria are gram - acid fast +
transmission of TB?
almost always through lung inhalation to lymph nodes, kidneys, bones, and CNS by hematogenous spread
to GI from swallowing infected sputum.
response of immunocompetent host vs immunosuppressed
immunocompetent - raises strong CMI response, holding infection at latent stage for decades
reactivation
describe the spread of TB through the body
hematogenous spread through infected trojan horse macrophages
activated ones clear it, cd8 cells kill infected macrophages and establish granulomas to contain infection
describe classic pulmonary TB
what to look for?
75%. cough, weight loss (consumption), fever, night sweats, hemoptysis, chest pain.
check sputum and x-ray. should see pink (Acid fast) rod chains in sputum.
describe extrapulmonary manifestations of TB
generally reactivations - scrofula in neck, genitourinary, CNS( meningitis or abscesses), skeletal (long bone or spine), GI(rare)
TB in pediatric patients
must have been recently aquired, watch for miliary & meningitis (deadly)
determine exposure to TB via
TST (injection under skin) and/or IGRA. perform abx resistance testing as soon as cultures grow
how to treat tb?
directly observed therapy with 4+ drug regimine including isoniazid.
Isolate patient for 2 weeks
describe the TB vaccine
live, attenuated M.Bovis used abroad, not un US. Not cost-effective here, can create weak-moderate false positive TST
most helpful factors for reducing incidence of TB in a population?
good diet, housing.
latent cases not infections
atypical mycobacteria are…
environmentally acquired infections tthat cause neither TB nor leprosy
atypical mycobacterial infection in an immunocompetent patient is ussually..
cutaneous- scrofula in children
immunosuppressed hosts may have systemic symptoms that mimic TB, particularly from M.kansasii or MAI/C
atypical mcobacgeria infection treatment
difficult once established - requires multiple antibiotics
m. leprae has no
in vitro culture system
m.leprae has an extremely long
incubation period, doesnt trasnmit easily. only 5-10% of humans beleived susceptible.
Range of hasens disease?
hansens disease is leprosy. ranges from
tuberculoid (paucibacillary, virgorous CMI both contains infection and damages nerves, ppd+
to
lepromatous (multibacillary, weak CMI, extensive cutaneous symptoms, PPD neg)
leprosy treatment?
2 years dapsone and rifampin
tuberculosis unique structure?
stains acid-fast
tuberculosis host and resovoir?
humans
transmission of tuberculosis?
inhalation, 10 or fewer infectious units
pathogensis of TB
proliferates in mononuclear phags, uses them to travel to extrapulmonary sites
leads to latent (immunocompetent) or active (immunocompromised) individuals.
speed of M.Leprae growth?
14 day doubling time, slowest growing human pathogen.
two pathogenisis pathways of leprae
- mild pacibacillary tuberculoid leprosy - presents as few skin lesions with few bacteria
more sever lepromatus form - presents more damange and nerve damage.
why differentiate TB and m.kansasii if they have similar symptoms and drug profiles?
trace for contacts with TB, kansaii is environmental.
TB will grow in vitro (TF)
T
what factors present challenges in diagnosing TB?
many different possible sets of symtpoms affecting different organs
lak of definitive single lab test like urine antigen alisa.
