March 20, 2023 – When a bacterial infection enters the bloodstream, every second counts. The patient's life is at stake. But blood tests to discover the bacteria take hours to days. While waiting, doctors often prescribe broad-spectrum antibiotics within the hope of killing the possibly causative germ.
Soon, that wait time might be significantly reduced, allowing healthcare providers to search out the most effective antibiotic for every infection more quickly – because of an innovation from Stanford University that identifies bacteria in seconds.
The cutting-edge method relies on tried-and-tested technology: an inkjet printer, much like the one you may have at home, except that it has been modified to print blood as an alternative of ink.
This “bioprinter” rapidly spits out tiny drops of blood – greater than 1,000 per second. When a laser is geared toward the drops – using a light-based imaging technique called Raman spectroscopy – the bacteria's unique cellular “fingerprint” becomes visible.
The very small sample size—each drop is 2 trillionths of a liter, a couple of billion times smaller than a raindrop—makes it easier to detect bacteria. Smaller samples mean fewer cells, so lab technicians can more quickly separate the bacterial spectra from other components, similar to red and white blood cells.
To increase efficiency even further, the researchers added gold nanoparticles that attach themselves to the bacteria and focus the sunshine like antennas. Machine learning – a form of artificial intelligence – helps interpret the sunshine spectrum and recognize which fingerprint belongs to which bacteria.
“It turned into a really interesting period in history where we were able to put together the pieces of different technologies, including nanophotonics, printing and artificial intelligence, to accelerate the identification of bacteria in these complex samples,” says study writer Jennifer Dionne, PhD, associate professor of materials science and engineering at Stanford.
Compare that to blood culture tests in hospitals, where it takes days for bacterial cells to grow and multiply in a big machine that appears like a refrigerator. Some bacteria, like people who cause tuberculosis, take weeks to culture.
Further tests are then needed to search out out which antibiotics fight the infection. The recent technology from Stanford could also speed up this process.
“The promise of our technique is that you don't need a cell culture to apply the antibiotic,” says Dionne. “We found that we can use Raman scattering to determine – even without incubating with antibiotics – what drug the bacteria would respond to, and that's really exciting.”
If patients receive the antibiotic most appropriate for his or her infection, treatment outcomes are prone to be higher.
“It can usually take 48 to 72 hours to get the blood culture results. Then your clinical decisions and antibiotic adjustments are based on those blood cultures,” says Dr. Richard Watkins, an infectious disease physician and professor of medication at Northeast Ohio Medical University. (Watkins was not involved within the study.)
“Sometimes, despite all your suspicions, you're wrong,” says Watkins, “and of course there can be a negative outcome for the patient. So if you can diagnose the pathogen earlier, that's ideal. Whatever technology allows doctors to do that is definitely an advance and a step forward.”
On a worldwide level, this technology could help reduce the overuse of broad-spectrum antibiotics, which contributes to the emergence of antibiotic resistance, a brand new health threat, Dionne says.
The team is working to further develop the technology and create an instrument the scale of a shoebox. After further testing, the product can then be delivered to market. This could take several years.
The potential of this technology extends beyond bloodstream infections. It may be used to discover bacteria in other fluids, similar to wastewater or contaminated food.