Mycobacterial genomic DNA from used Xpert MTB/RIF cartridges can be utilised for accurate secondline genotypic drug susceptibility testing and spoligotyping
Date
2017-11-01
Journal Title
Journal ISSN
Volume Title
Publisher
Springer Nature
Abstract
ENGLISH ABSTRACT: Xpert MTB/RIF (Xpert) is a widely-used test for tuberculosis (TB) and rifampicin-resistance. Second-line
drug susceptibility testing (DST), which is recommended by policymakers, typically requires additional
specimen collection that delays effective treatment initiation. We examined whether cartridge extract
(CE) from used Xpert TB-positive cartridges was, without downstream DNA extraction or purification,
suitable for both genotypic DST (MTBDRplus, MTBDRsl), which may permit patients to rapidly receive a
XDR-TB diagnosis from a single specimen, and spoligotyping, which could facilitate routine genotyping.
To determine the limit-of-detection and diagnostic accuracy, CEs from dilution series of drug-susceptible
and -resistant bacilli were tested (MTBDRplus, MTBDRsl). Xpert TB-positive patient sputa CEs (n = 85)
were tested (56 Xpert-rifampicin-susceptible, MTBDRplus and MTBDRsl; 29 Xpert-rifampicin-resistant,
MTBDRsl). Spoligotyping was done on CEs from dilution series and patient sputa (n = 10). MTBDRplus
had high non-valid result rates. MTBDRsl on CEs from dilutions ≥103CFU/ml (CT ≤ 24, >“low” Xpert
semiquantitation category) was accurate, had low indeterminate rates and, on CE from sputa, highly
concordant with MTBDRsl isolate results. CE spoligotyping results from dilutions ≥103CFU/ml and sputa
were correct. MTBDRsl and spoligotyping on CE are thus highly feasible. These findings reduce the need
for additional specimen collection and culture, for which capacity is limited in high-burden countries,
and have implications for diagnostic laboratories and TB molecular epidemiology.
Description
CITATION: Venter, R., et al. 2017. Mycobacterial genomic DNA from used Xpert MTB/RIF cartridges can be utilised for accurate secondline genotypic drug susceptibility testing and spoligotyping. Scientific Reports, 7:14854, doi:10.1038/s41598-017-14385-x.
The original publication is available at http://www.nature.com
Publication of this article was funded by the Stellenbosch University Open Access Fund.
The original publication is available at http://www.nature.com
Publication of this article was funded by the Stellenbosch University Open Access Fund.
Keywords
Mycobacterium tuberculosis, Genomes -- DNA, Pharmacogenomics -- Testing
Citation
Venter, R., et al. 2017. Mycobacterial genomic DNA from used Xpert MTB/RIF cartridges can be utilised for accurate secondline genotypic drug susceptibility testing and spoligotyping. Scientific Reports, 7: 14854, doi:10.1038/s41598-017-14385-x