Lab-on-a-chip promises rapid 'superbug' diagnosis

A newly developed diagnostic chip could help in the treatment of antibiotic resistant infections by reducing the testing time for superbugs from days to around one hour.

The new device developed by researchers at the University of Toronto - and described in the journal Lab on a Chip - could help doctors pick the most effective antibiotic to treat infections and avoid having to use less precise so-called broad-spectrum antibiotics that can sometimes lead to increased resistance.

The chip works by concentrating bacteria in a miniscule space - just two nanolitres in volume - in order to increase the effective concentration of the starting sample.

It achieves this high concentration by ‘flowing’ the sample, containing the bacteria to be tested, through microfluidic wells patterned onto a glass chip.

At the bottom of each well a filter, composed of a lattice of tiny microbeads, catches bacteria as the sample flows through. The bacteria accumulate in the nano-sized well, where they’re trapped with an antibiotic and a signal molecule called resazurin.

Living bacteria metabolize resazurin into a form called resorufin, changing its electrochemical signature. If the bacteria are effectively killed by the antibiotic, they stop metabolizing resazurin and the electrochemical signature in the sample stays the same. If they are antibiotic-resistant, they continue to metabolize resazurin into resorufin, altering its electrochemical signature. Electrodes built directly into the chip detect the change in current as resazurin changes to resorcin.