Cantilevers that Sense Bacteria Could Save Your Life

(Last Updated On: February 11, 2016)

Hammock MC900355421 200pxScience Fact:  A news item about nanoscale “cantilevers” may hold the answer to a serious problem facing hospitals.  If you arrive at a hospital with a serious bacterial infection, you may have only a few hours to live unless the physicians can decide which antibiotic will be effective against your infection.  It takes several days to culture the bacteria with various antibiotics, to see which one stops the bacteria from multiplying.  By then you could be dead.  What to do?

A group of researchers in Lausanne, Switzerland invented a novel way to rapidly distinguish between live and dead bacteria.  It uses nanotechnology to fabricate a tiny cantilever — think of a diving board, anchored at one end and slightly flexible.  These cantilevers are typically made of silicon, a material that can readily be nanofabricated.  The cantilever is coated with bacteria and its position is precisely measured with a laser; this is analogous to the way your local highway patrol measures your car speed.  The laser detects vibration in the cantilever, that is, bouncing up and down.

What the research group found is that when the bacteria are alive, the cantilever bounces away, apparently as a result of chemical processes within the bacteria.  But when the bacteria are immersed in an antibiotic solution that kills them, the vibration disappears, within five minutes.

If this talk of cantilevers is too much to handle, think of it this way.  Instead of a diving board, consider a hammock.  If there’s no breeze, an empty hammock will rest quietly.  Put a sleeping person into it like the snoozing fellow in the drawing, and the hammock will sway slightly, as he breathes and moves around in his sleep.  So the normal movements of a living creature are enough to set up an oscillation that can be detected.

When this technique is built into a device for use in a hospital, bacteria from a patient would be smeared on a number of these cantilevers.  Various antibiotics would be applied, identifying the most useful antibiotic in minutes, so the patient could be immediately treated.

Science Speculation:  But please allow me to play the skeptic!  A significant question has been left unanswered: what exactly is it about bacterial metabolism that causes the cantilever to vibrate?  When the vibration goes away, are the bacteria truly dead, or just taking a nap?  Is this vibration characteristic of all bacteria, or just certain ones?  What are the limitations on using this to detect life?

Every research project leaves a lot of unanswered questions, and thoughtful researchers, including the Swiss team, point these out.  Those open questions should remind us to take the results with caution.  When the mechanisms and limitations are understood, several things could happen:  this could turn out to be a significant advance in medical diagnosis;  it could be a specialized result that for practical reasons can’t be widely used in a hospital setting;  or it could open a new door to understanding how bacteria metabolize energy and interact with their surroundings.  Watch this space!

Cantilevers vibrating with bacteria: is this a basis for a new diagnostic tool?  A case of speculation getting ahead of the facts? What do you think?

Sources:
http://www.sciencemag.org/news/2013/06/microscopic-tuning-forks-could-make-difference-between-life-and-death-hospital
http://www.nature.com/nnano/journal/v8/n7/full/nnano.2013.120.html

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