TB Flashcards
what pathogen is responsible for the cause of most tb
M. tuberculosis causes most TB cases.
name the type of mycobacteria that can cause TB
M. tuberculosis M. bovis M. africanum M. microti M. canetti
name a mycobacteria that does not cause TB
M. avium complex
how is TB spread
TB is spread person to person through the air via droplet nuclei
M. tuberculosis may be expelled when an infectious person: Coughs Sneezes Speaks Sings
- then the transmission occurs when another person inhales the droplet
what does the probability that TB will be transmitted depend on
Infectiousness of person with TB disease
Environment in which exposure occurred
Length of exposure
Virulence (strength) of the tubercle bacilli
what is the best way to stop transmission
Isolate infectious persons
Provide effective treatment to infectious persons as soon as possible
what is latent TB
this is when a person is infected with TB but the TB is not yet active
How do you diagnose those with latent TB
- Mantoux test with PDD
- gamma interferon release assays (IGRA)
how long is the incubation period of active TB
incubation period of active TB typically 3-9 months and almost always under two years
most people who have active TB are…
reinfected with TB it is not latent TB becoming activated
How many people have latent TB
About 1.7 billion people, 23% of the world’s population, are estimated to have a latent TB infection
what are the breakthrough drugs in the 1940s and 1950s that can kill TB
Streptomycin (SM) discovered in 1943
Isoniazid (INH) and
p-aminosalicylic acid (PAS) discovered between 1943 and 1952
what is the treatment of drug sensitive TB
RIPE
- Rifampicin
- Isoniazid
- Pyrazinamide
- Ethambutol
- Rifampicin and Isoniazid for 4 moths
- pyrazinamide and ethambutol for 2 months
- daily therapy (or 3 times a week)
- orally
- 12 months for TB meningitis
what are the baseline checks for TB
- chest x ray
- liver function tests
- fasting blood sugar test
- urea and electrolyte test
- c reactive protein test
what are the countries high in TB in the EU
Armenia, Azerbaijan, Belarus, Bulgaria, Estonia, Georgia, Kazakhstan, Kyrgyzstan, Latvia, Lithuania, Moldova, Romania, Russia, Tajikistan, Turkey, Turkmenistan, Ukraine and Uzbekistan
what is MDR tb
this is multi drug resistant to TB - Resistant to INH and RIF (“ MDRTB) PLUS Resistance to amikacin, kanamycin or capreomycin (injectable agents) AND Resistance to any fluroquinolone
what 3 countries account for almost half the worlds cases of MDR
- india
- china
- Russian federation
who usually gets XDR-TB (extensively drug resistant TB)
Most were pulmonary Most were male Most aged 20-50 Most had had previous TB Most born abroad. Distributed
how do you improve diagnosis of TB
- Improve diagnostic capacity: infrastructure, training
- Export patient materials to central facilities
- Improve transport
- Improve stability of biomaterials
- Combination of above
Lateral thinking - Clinical
- Radiological
- Laboratory-Diagnosis TB
- Laboratory-DST
- Microscopy, culture, molecular
how is the TB culture use
Solid + rapid liquid systems
Sensitive for diagnosis
Slow but faster for liquid eg approx 10-21 days for smear positive sputum specimens
Also for drug resistance
- more expensive
- supply chain is critical
how do you do rapid diagnosis of resistance to RIF and INF
molecular line probe assays
how do molecular line probe assays work
1, DNA extraction from cultures and clinical specimens (sputum);
2, PCR amplification of fragments of genes associated with drug resistance;
3, Hybridization with the DNA probes on membranes;
4, Development, reading and interpretation of results
