Rapid Tuberculosis Diagnostics Including Molecular First- and Second-Line Resistance Testing Based on a Novel Microfluidic DNA Extraction Cartridge

Abstract

Xpert MTB/RIF testing has improved tuberculosis (TB) diagnostics and rifampicin (Rif) resistance testing worldwide. However, it has weaknesses, such as its restriction to Rif resistance testing and the inability to use extracted DNA for further testing. Herein, a holistic diagnostic workflow, including TB detection and resistance testing toward Rif, isoniazid, and important second-line drugs (SLDs), based on a novel microfluidic DNA extraction cartridge (TB-Disk), is presented. DNA from 73 precharacterized sputum samples was extracted with TB-Disk, including 45 clinical and bacteriologically confirmed TB samples, nine TB-negative samples, and 19 sputum samples spiked with twofold dilutions of TB bacteria. The extracted DNA was subjected to further testing with FluoroType MTB (FT-MTB), GenoType MTBDRplus (GT-plus), and GenoType MTBDRsl. A total of 100% (20/20) and 72% (18/25) of smear-positive and smear-negative TB samples were identified as Mycobacterium tuberculosis complex positive. A total of 79% (33/42) of subsequently GT-plus tested samples yielded a valid result. Eight samples were identified as multidrug-resistant TB by GT-plus and further tested for resistance toward SLDs using GenoType MTBDRsl, yielding 75% (6/8) valid results. FT-MTB with cartridge-based DNA extraction (Disk-DNA) and DNA extracted with FluoroLyse yielded similar analytical sensitivities. FT-MTB with Disk-DNA was 100% specific. TB-Disk in combination with FT-MTB enables sensitive TB detection. The Disk-DNA can be further used for screening resistance toward first-line drugs and SLDs.