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New technology speeds testing for bacteria's resistance

June 1, 2015
by Richard R. Rogoski
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Researchers at the University of Toronto have developed a diagnostic chip that can cut testing time for antibiotic-resistant bacteria from days to about one hour.

Based on an electrical and biomedical engineering design, the chip concentrates bacteria into a miniscule space of just two nanoliters in volume. This higher concentration is achieved by “flowing” the sample containing bacteria through microfluidic wells within a glass chip. Since each well contains a filter made of tiny microbeads, the bacteria accumulate at the bottom of each well where they are trapped with an antibiotic and a signal molecule called resazurin.

Electrodes built into the chip detect changes in current if the bacteria metabolizes resazurin. If the antibiotic kills the bacteria, metabolizing is halted and the electrochemical signal stays the same.

“Guessing can lead to resistance to these broad-spectrum antibiotics, and in the case of serious infections, to much worse outcomes for the patient,” said researcher Justin Besant in a press release. “We wanted to determine whether bacteria are susceptible to a particular antibiotic, on a timescale of hours, not days.”

Professor Ted Sargent of The Edward S. Rogers Sr. Department of Electrical & Computer Engineering, added: “Our approach is the first to combine this method of increasing sample concentration with a straightforward electrochemical readout. We see this as an effective tool for faster diagnosis and treatment of commonplace bacterial infections.”