ScreenTape as a tool for the rapid differentiation of Mycobacterium tuberculosis isolates.

Abstract The emergence of difficult to treat multi drug-resistant tuberculosis currently threatens control efforts in all regions of the world. Genotyping of M. tuberculosis strains using molecular markers has the potential to identify outbreaks and track transmission of drug resistant strains. To be of value to the public health practitioner genotyping must be discriminatory, rapid and readily available. The preferred method of typing M. tuberculosis is MIRU-VNTR where 15 loci are examined by PCR. However, implementation requires the ability to accurately size the resulting amplicons. Analysis by traditional gel electrophoresis is tedious and slow and MIRU typing has so far been largely restricted to laboratories with sophisticated high throughput analytical facilities. ScreenTape (LAB901, Loanhead, Scotland) is a fully automated electophoretic device for rapid analysis of nucleic acids. It is simple to use and provides accurate sizing of amplicons in under 10 min. When applied to MIRU-VNTR analysis of 20 drug resistant M. tuberculosis isolates, the assignment of alleles was in agreement with results obtained from a commercial genotyping company on 97.1% occasions, compared to 93.4% for traditional gel electrophoresis. Correlation coefficients for predicted fragment length were 0.9911 and 0.9919 for ScreenTape and gel electrophoresis, respectively. Whereas the 20 isolates had previously been identified as having two spoligotype patterns, 14 MIRU patterns were observed demonstrating the superior discriminatory power of MIRU-VNTR typing for M. tuberculosis. ScreenTape appears to offer rapid discriminatory genotyping and may prove an attractive option for public health laboratories charged with controlling infectious tuberculosis disease.