Cantilever Detects Bacterial Motion

in NEWS

Shows Promise as Screening Technology for Antibiotics

By Mark Dwortzan

Illustration of a microcantilever sensor with E. coli bacteria attached, with close-up of a single bacterium (inset). The motion of the bacteria couple to the cantilever, and the cantilever motion is detected using an optical technique.
Illustration of a microcantilever sensor with E. coli bacteria attached, with close-up of a single bacterium (inset). The motion of the bacteria couple to the cantilever, and the cantilever motion is detected using an optical technique.

Determining the most effective treatment for a bacterial infection can take several days as clinicians culture bacteria from a sample of the infected site, test their response to different antibiotics, and home in on the best choice. Meanwhile, patients receive broad spectrum antibiotics that could be far less effective, leaving them prone to spreading the infection and generating antibiotic-resistant bacteria. Now a new technique developed and evaluated by a team of researchers from the Boston University College of Engineering, Stanford University School of Medicine, and Virginia Tech may ultimately reduce antibiotic susceptibility testing time to a matter of minutes and thus enable more precise and effective prescriptions.

The technique centers on a silicon microcantilever designed by Associate Professor Kamil Ekinci (ME) that’s sensitive enough to reveal whether or not onboard bacteria—captured on the surface by a chemical that bonds to their cell walls—are still “alive and kicking” rather than stilled forever by a successful antibiotic. A laser beam continuously reflects off the surface, indirectly detecting subtle, low-frequency vibrations of the diving-board-like cantilever that are caused entirely by bacterial motion.

In recent experiments funded by the National Science Foundation and National Institutes of Health, the researchers attached a layer of E. coli bacteria to the cantilever, applied the antibiotic streptomycin, and observed a cessation of bacterial motion within 30 minutes. They published their results in the journal Applied Physics Letters.

The study provides a new platform for improving our understanding of the mechanisms behind the motion of and communication among microorganisms—key factors in bacterial infections and antibiotic resistance—and for developing a disposable, microfluidic chip to diagnose bacterial infections and pinpoint suitable antibiotics.

“Ultimately, the cantilever and optical measuring instruments could be incorporated into a compact, user-friendly device that clinicians could use to test a patient’s bacteria sample for antibiotics susceptibility,” said Ekinci.