Some bacterial infections are so severe that if the right antibiotic is not given straight away, there is a high chance the patient will die. But unfortunately with current methods it can take days if not weeks to test a bacterium’s response to treatment. Now researchers in Switzerland have developed a test based on nano-sized “tuning forks” that could cut this timescale to minutes and thereby save lives.

At present, to find out if a bacterium is responding to antibiotic treatment, clinicians have to wait and see what happens when they try to grow it in a culture. For some types of bacteria, such as the one that causes tuberculosis (TB), this can take up to a month.

The nano-sized “tuning forks” that the researchers in this new study have developed are tiny and extremely sensitive cantilevers, thinner than human hair, that can pick up almost imperceptible atomic-level vibrations emitted by live bacteria.

Researchers from Ecole Polytechnique Fédérale de Lausanne (EPFL) report how they developed and demonstrated the technology in a study published online in Nature Nanotechnology on 30 June.

“Here we show that the fluctuations of highly sensitive atomic force microscope cantilevers can be used to detect low concentrations of bacteria, characterize their metabolism and quantitatively screen (within minutes) their response to antibiotics,” they write.

Live bacteria are busy with metabolic activity, the set of life-sustaining chemical reactions that goes on in living cells. The researchers propose that it is this metabolic activity that sends out the tiny vibrations that their technology detects.

Placing the bacteria on or near the nano-sized tuning forks or cantilevers causes them to oscillate in response to the bacterial vibrations. The oscillations are very small, of the order of one millionth of a millimeter.

By projecting a laser beam onto the cantilever and picking up how the light is reflected back, the researchers convert the oscillations into electrical signals that can be read easily.

When the electrical signal is a flat line, it means there are no live bacteria. An effective way to find out very quickly whether treatment with an antibiotic has had the desired effect. This is especially useful for testing resistant strains.

Study author Giovanni Dietler, a physicist who investigates properties of living materials, says in a statement:

“This method is fast and accurate. And it can be a precious tool for both doctors looking for the right dosage of antibiotics and for researchers to determine which treatments are the most effective.”

“We applied this methodology to Escherichia coli and Staphylococcus aureus, showing that live bacteria produced larger cantilever fluctuations than bacteria exposed to antibiotics,” write the authors.

The researchers have miniaturized their technology so it fits in a device the size of matchbox, making it easily portable for clinical use.

Dietler says they could make it even smaller:

“By joining our tool with a piezoelectric device instead of a laser, we could further reduce its size to the size of a microchip,” he explains.

And he also sees it may be possible to develop a version that can test a series of antibiotics on one strain in only a few minutes.

The researchers suggest their nano-sized tuning forks could also be useful for testing response to chemotherapy treatment.

They are currently looking at a way to use their nano-sized tuning forks to measure the metabolism of tumor cells that have been exposed to chemotherapy.

Again, as with bacterial infections, the huge advantage would be to see within minutes instead of weeks, whether the cancer was responding to treatment.

Another way scientists are using nanotechnology in medicine is to target therapy at the cellular level. For example, one group at MIT in the US has developed an approach that could be used to create “nano-factories” that make protein-based drugs at tumor sites to fight cancer.