May2 M3-Tuberculosis Flashcards
(imp) most important consideration in diagnosing TB
think of the epidemiologic probability
TB infection definition
-carrier state
-infected, healthy and not contagious
(sometimes called latent)
-CXR and culture negative
-PPD positive
tuberculosis definition
- disease state
- contagious
- culture positive
- CXR positive
- PPD negative
mycobacterium def
genus of the mycobacteria. most mycobacteria are harmless (NTM = non tuberculous mycobacteria)
pathogen of tuberculous infection and tuberculosis disease
mycobacterium tuberculosis
definitive host of mycobacterium tuberculosis
humans (only)
how tuberculosis risk varies on a graph after exposure to M. TB pathogen
increases as years after exposure increase
there is NO bimodal distribution and no clear cut between primary and latent TB
why TB is said to be a symbiont
- symbiosis = divergent organisms (humans and M. TB) live together in a fine balance
- TB does enough pathology to transmit but not enough to kill the host (the reservoir)
example of lung pathology in someone with tuberculosis
localized, chronic pathology, one cavity and rest of the lung is fine.
vaccine of TB and benefits vs problems
BCG
- medical impact (stops children from being infected. protects 80% of children from pediatric TB)
- NO public health impact (adults are still contagious)
events that made TB rates go up
when life conditions get worse basically
- WWI and WW2
- famines
(imp?) what is the risk of tuberculosis after tuberculosis infection
10% lifetime risk
- 5% in first 2 years after infection (1 in 40 chance per year)
- 5% for the rest of your life (1 in 1000 chance per year per year)
when do you get the most benefit out of treating latent TB
treat TB infection as early as possible is the best
1st step of pathogenesis in TB infection
- aerosol travers to lung and encounters ALVEOLAR MACROPHAGE FIRST
- macrophage eats it (done, no infection) or delivers it to DENDRITIC cell that brings it to lymph node
what happens if TB brought to lymph node and its replication is permitted
- replication of TB in the lung, if permitted by alveolar macrophages, = get Ghon focus
- bc brought to lymph nodes, get adaptive immunity and granuloma forms
clinical significance of M. TB being brought to the lymph node
because get adaptive immunity, the PPD test will be positive (cell-mediated immunity = type IV HS rx)
what can happen after M. TB brought to lymph nodes and granuloma forms
can get:
- chronic localized lymphadenitis (containment)
- spread through lymphatics in lungs or outside the lungs and in blood possibly (dissemination)
possible complication of M.TB going to lymph nodes
infected lymph nodes (NOT reative) can compress bronchi and lead to bronchial pneumonia or post obstructive bronchial pneumonia
content of granuloma
middle = M.TB
around = lymphocytes and macrophages (some of the macrophages are infected)
around that = fibrous ring
pathology of when tuberculosis infection becomes tuberculosis
- M. TB breaks from granuloma and spills in airways
- sputum and breathing = become contagious (but may not be sick initially)
- become sick as pathogen progresses
- if get disseminated, extrapulmonary TB = lethal to host and pathogen, TB meningitis possible
species where TB can be and definitive host
- can be in humans, animals, cattle
- definitive host = humans
% of world population infected with TB and nbr of people with tuberculosis
- quarter of world population has TB
- 10-15M walking around with tuberculosis (contagious)
number 1 cause of infectious mortality in the world
tuberculosis (1.7M deaths per year)
- 1.3M deaths per year (TB)
- 0.4M deaths per year (HIV or AIDS + TB)
how HIV and TB interact
- TB accelerates HIV progression to AIDS
- HIV accelerates progression of TB infection to tuberculosis disease
symptoms of TB
- cough with sputum, maybe blood
- fever
- sweats
- weight loss
- consumption
what’s miliary TB
TB everywhere and there is no containment
most important consideration in doing a TB dx
epidemiologic probability
physical exam and investigations of TB
- lung auscultation
- CXR (FOR TB DISEASE)
- PPD test FOR LATENT (TB infection)
- path lab for granulomas, acid-fast staining, PCR=gold std
why M. TB culture is essential in a sick patient even when you already have a dx
to test for drug susceptibility
why treat TB (Abx)
reduce mortality, morbidity and spread
considerations in TB tx
- same for immunocompetent and deficient
- MDR TB exists and can spread, XDR (extensively drug resistant is worse)
- several weeks to get susceptibility data
4 drugs you start with in TB (to make sure at least 2 are active)
- isoniazid
- rifampin
- ethambutol
- pyrazinamide
duration of the short course tx of TB
24 weeks
2 types of testing for TB infection
- tuberculin skin test (TST): give Ags to the patient
- IFN-g release assays: bring patient’s lymphocytes to the Ags
treatment of drug-sensitive TB INFECTION
- isoniazid for 9 months
- rifampin for 4 months
treatment of drug-resistant TB INFECTION
monitor clinically
what can you predict when you see TB rates increasing in a population
drop in life expectancy in years to come
what would be a good TB vaccine
vaccine that prevents contagion: only way TB can be fought
