March 20, 2023 — When a bacterial infection reaches the bloodstream, every second is critical. The patient’s life is at stake. Yet blood tests to identify the bacteria take hours or even days. In the meantime, doctors often prescribe broad-spectrum antibiotics in hopes of killing the offending germ.
One day soon, that wait time could drop dramatically, allowing healthcare providers to focus more quickly on the best antibiotic for each infection — thanks to a Stanford University innovation that identifies bacteria in seconds. .
The state-of-the-art method relies on old-school technology: an inkjet printer, similar to the one you might have at home, except this one has been modified to print blood instead of ink .
This “bio-printer” rapidly spits out tiny drops of blood – more than 1,000 per second. Shine a laser on the drops – using a light-based imaging technique called Raman spectroscopy – and the bacteria’s unique cellular “fingerprint” is revealed.
The very small sample size – each drop is two trillionths of a litre, about a billion times smaller than a raindrop – makes it easier to detect bacteria. Smaller samples mean fewer cells, so lab technicians can more quickly separate bacterial spectra from other components, such as red blood cells and white blood cells.
To further increase the effectiveness, the researchers added gold nanoparticles, which attach to the bacteria, serving as antennae to focus the light. Machine learning – a type of artificial intelligence – helps interpret the spectrum of light and identify which fingerprint matches which bacteria.
“It ended up being this really interesting historical period where we could put the pieces of different technologies together, including nanophotonics, printing and artificial intelligence, to help speed up the identification of bacteria in these complex samples,” says study author 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 inside a large machine that looks like a refrigerator. For some bacteria, such as those that cause tuberculosis, cultures take weeks.
Then, further tests are needed to identify the antibiotics that will suppress the infection. New technology from Stanford could also speed up this process.
“The promise of our technique is that you don’t need to have a cell culture to apply the antibiotic on top,” says Dionne. “What we’re discovering is that from Raman scattering we can use that to identify – even without incubation with antibiotics – what drug the bacteria would respond to, and that’s really exciting.”
If patients can receive the best antibiotic for their infection, they are likely to have better outcomes.
“Blood cultures can typically take 48 to 72 hours to come back, and then you base your clinical decisions and adjust antibiotics on those blood cultures,” says Richard Watkins, MD, infectious disease physician and professor of medicine at Northeast Ohio Medical. University. (Watkins was not involved in the study.)
“Sometimes, despite your best guess, you’re wrong,” says Watkins, “and obviously the patient could have an adverse outcome. So if you can diagnose the pathogen earlier, that’s ideal. Whatever be the technology that allows clinicians to do this, it’s definitely progress and a step forward.
Globally, this technology could help reduce the overuse of broad-spectrum antibiotics, which contributes to antimicrobial resistance, an emerging health threat, Dionne says.
The team is working to further develop the technology into a shoebox-sized instrument and, with further testing, bring the product to market. It could take a few years.
This technology also has potential beyond blood infections. It could be used to identify bacteria in other fluids, such as sewage or contaminated food.