Researchers at the National Institute of Standards and Technology (NIST) have developed a method of testing that determines whether an antibiotic fights its targeted infection. The new technique is designed not only to speed effective treatment but also to limit the development of drug-resistant bacteria.
Bacteria’s motion tells the story
The technique uses a sensor that provides feedback in less than an hour and is designed around a quartz-crystal resonator. As bacteria adheres to the resonator, it is possible to sense the mechanical motion of microbes and their response to antibiotics.
How it works
A thin piezoelectric quartz disk is sandwiched between two electrodes. An alternating voltage at a stable frequency near the crystal’s resonant frequency is applied to one electrode to excite crystal vibrations. From another electrode on the opposite side of the crystal, researchers record oscillating voltages of the crystal response, a signal that shows fluctuations in the resonant frequency (or frequency noise) arising from microbial mechanical activity coupled to the crystal surface.
The ultra-sensitive approach enabled detection of cell-generated frequency fluctuations at a level of less than one part in 10 billion. The experiments showed that the amount of frequency noise was correlated with the density of living bacterial cells. When the bacteria were then exposed to antibiotics, frequency noise sharply decreased. Bacteria with paralyzed flagella were used in the experiments to eliminate effects of swimming motion. This enabled the researchers to conclude that the detected cell-generated frequency fluctuations arise from vibrations of cell walls.
To learn more about the NIST’s work in this area, see the news release and the researchers’ open-access published work in Scientific Reports.