Tuberculosis Diagnosis and Drug Sensitivity Testing

E Test
Company
In the FIND portfolio?
Principle
Stage of development
Advantages
Disadvantages
Interest in peripheral
laboratory settings?
MB redox®
Company
In the FIND portfolio?
Principle
Stage of development
Advantages
Disadvantages
Interest in peripheral
laboratory settings?
AB Biodisk (Sweden).
No.
10
The technique is based on determination of drug sensitivity testing using strips
containing gradients of impregnated antibiotics. The E Test strip is placed on the
surface of the solid culture medium and MICs (minimal inhibitory concentrations, a
measure of the susceptibility of a strain to an antibiotic) are determined by
interpreting the point at which the ellipse of inhibition crosses the strip.
Commercially available.
Simplicity, minimal training required.
Shown to be accurate and reproducible 15 .
Relatively fast (five to ten days after primary culture).
Requires high bacterial concentration for inoculum i.e. needs to start from a culture.
Simple approach that does not require particular training of technical personnel.
Requires an initial culture step, which significantly limits its advantages.
Biotest (Germany).
No.
This system is based on the reduction of a tetrazolium salt indicator in liquid
medium 16 . MB Redox® allows an easy macroscopic visualisation of the bacterial
growth. The tetrazolium salt indicator forms red to violet particles when reduced by
the growth of the mycobacteria.
Commercially available.
Simplified 96 well plate format, does not require specialised machine (can be read
by eye or simple spectrophotometer).
Cannot be used to measure DST on initially positive samples as dye is toxic;
visualisation is not easy; very few reports available; relatively slow (16 days for a
smear positive sample, 3 weeks for a negative result).
Interest would seem to be limited as better-performing alternatives exist.