By looking at the distinctive ways in which colonies of bacteria scatter laser light, US researchers have built a fast, cheap way of detecting the presence of potentially deadly microbes.
Inspectors in food processing plants currently culture samples in a Petri dish for 24 to 48 hours, before running biochemical analyses of any bacterial colonies that grow to see if they include dangerous species.
This is time-consuming and expensive, says J Paul Robinson, whose team at Purdue University in Indiana, US, devised the new, laser-based method. The device, called a laser scatterometer, can identify bacterial colonies after just a few hours of growth.
Bacterial colonies grow in complex structures that are specific to their species. When hit with a laser beam, Robinson and his colleagues have found that these structures scatter light into a unique pattern, akin to a fingerprint.
The patterns are projected onto a screen behind the Petri dish, and recorded with a digital camera. By analysing the resulting images mathematically, the researchers could recognise six different species of Listeria, bacteria commonly found in food, with 90% accuracy. They even managed to distinguish multiple species of the bacteria growing within the same culture. “We were genuinely surprised by our success,” says Robinson.
Once the scatterometer’s analytical software learns a bacterial pattern, it automatically recognises it in the future. Robinson aims to build a database of microbes that the system can identify without further human input.
The entire hardware for the system – consisting of a small laser diode, screen, Petri dish, computer, and digital camera – costs less than $1000.
Robinson’s team aims to see if the system can tell the difference between different strains of Staphylococcus aureus. Drug-resistant strains of this bacterium, which includes MRSA, are a menace in hospitals, where they can cause deadly infections.
“We haven’t shown it yet, but we’ve got the feeling we can detect resistance to antibiotics,” says Robinson. “Resistance comes from a biochemical change. If that’s expressed in the structure of the colony, we should be able to see it.”
Journal reference: Journal of Biomedical Optics (vol 11, p 034006)
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support.
