Disease: Magnetic tags to flag tuberculosis

A portable, low-cost diagnostic system for the detection of Mycobacterium tuberculosis (MTB) is reported in Nature Communications this week. The device works with minimally processed mucus samples and delivers results within just 2.5 hours.

The rapid identification of patients infected with MTB, especially its drug-resistant forms, is important for public health and global tuberculosis control. However, this often poses a challenge, particularly in resource-constrained environments, as common diagnostic tests either require complicated optical systems and stable power supply or take weeks to deliver results. Ralph Weissleder and his team developed a test, which detects magnetically labelled pieces of bacterial DNA using magnetic resonance measurements. The device successfully detected MTB in patient mucus samples and was capable of distinguishing multidrug-resistant MTB specimens that harbour specific genetic mutations in a single nucleotide.

As magnetic assays are less prone to interference than optical methods, mucus samples only need to be mixed with glass beads to extract DNA, with no further purification required. Unlike optical systems, the measurement setup can also be easily packaged as a miniaturized, portable electronic and microfluidic device, on which all subsequent analytic steps are performed.