Mi - TB Flashcards
what % of the world are infected with TB
33%
in whom is TB more common in UK
homeless
Big towns like London / Leicester
how many new cases of TB are there every year
10 million
what is the biggest risk factor of TB
poverty
why can TB cause poverty
stigmatised - attached to HIV
reduced QoL and working life
where is drug resistant TB most common
Russia
Asia
what bacteria causes most TBs
mycobacteria tuberculosis
name other bacteria that can cause TB
m.tuberculosis (1)
m.bovis
m.africanum
m.microti
m.canetti
who/what gets m.bovis TB
cattle / badgers
which mycobacteria do NOT cause TB
m.avium
m.chelonae
m.abscessus
m.chimaera
what does TB look like under microscope
sputum smear positive bacteria
bascillus
who gets m.abscesus
CF pts
who gets m.avium
HIV pts
who gets m.chimaera
vascular bypass device pts
what does m.chelonae cause
ulcerating, crusting skin lesion
how is TB spread
via droplet nuclei in the air (aerosol)
what 4 factors does the probability that TB will get transmitted depend on
infectiousness of person with TB
environment in which exposure occured
length of exposure
virulence of tubercle bacilli
what is the best way to stop transmission
isoaltion
treat infected person
what lifetime % of TB infected people go on to become unwell with TB
10%
what lifetime % of TB infected HIV pts go on to become unwell with TB
30-50%
how do you prevent latent TB becoming active
diagnosis + chemoprophylaxis
Sx of TB
fever, weight loss, night sweats, 2-3 weeks cough
how is latent TB infection diagnosed
mantoux with PPD or gamma interferon release assays (IGRA)
what is incubation period of TB
3-9 months but always UNDER 2 YEARS
are most people unwell with TB unwell do to reactivation of latent TB or reinfection?
exogenous reinfection
what 4 drugs are used in Mx of TB
RIPE
rifampicin
isoniazid
pyrazinamide
ethambutol
what is the drug Tx regime inc timings for TB
RIPE for 2 months
rifampicin and isoniazid for 4 months
(total 6 months)
daily therapy, orally
what baseline checks are done when someone is on drug Tx for TB
baseline CXR, LFTs, FBC, U&Es, CRP
when is the drug Tx regime extended in TB and to how long
TB meningitis
12 months Tx
what % of TB must be eradicated in a country for that country to be TB free
80%
what is the turn around time for a microscopy ZN stain for TB detection
30 mins
what is the turn around time for a solid culture for TB detection
4-6 weeks
which 3 countries have the highest rates of drug resistant TB
india
china
russia
what factor influences the prognosis of someone with multidrug resistant TB and HIV
whether they get the correct drug regime or not
how does TB become multi drug resistant
resistance is a natural phenomenon
poor Tx encourages resistance
selection pressures and advantages increase prevalence of the resistance
how is drug resistant TB reduced
use multiple drugs to treat TB
how can drug resistant TB be quickly diagnosed
molecular line probe assays using PCR
how can whole genome sequencing be used in TB diagnosis
speciation - is the mycobacterium TB causing or not
relatedness - transmission and tracking
drug resistant or not
give 4 steps in next generation sequencing for whole genome sequencing in TB
cultivation of pathogen
DNA extraction
library preparation
sequencing
how much more expensive is it to treat multi drug resistant vs drug sensitive TB
10x more
what % of mutli drug resistance TB can be predicted by WGS
90%
what is the gene for rifampicin resistance
RPOB
what is the efficacy of BCG vaccine
70%
