New technology creates 3D images of bacteria for antibiotic susceptibility tests

Researchers at the University of Connecticut have developed a highly sensitive image sensor that can quickly and accurately monitor bacterial growth. The technique involves shining laser light through a bacterial sample and capturing images in multiple orientations before reconstructing the diffracted light patterns to create a 3D image of the bacterial colony. These 3D images provide significant details about the growth and properties of bacteria and could be very helpful in quickly identifying which antibiotics are most effective at killing them.

Determining antibiotic sensitivity is a tedious process. A sample of bacteria isolated from a patient is typically grown on a nutrient medium such as agar. Once enough bacteria are present, which can take several days, laboratory technicians expose them to various antibiotics. Only then can they assess whether the bacteria are susceptible to certain drugs.

This can take too long to wait for someone with a dangerous infection. Therefore, the development of faster antibiotic susceptibility tests is an active area of ​​research. This latest technology relies on 3D imaging of the bacteria to provide more information than traditional 2D images. For example, if a bacterial colony grew upward but not outward, conventional imaging would not readily reveal it, which means that laboratory technicians would assume the colony was not growing at all.

Conversely, this new technique will reveal such growth and provide a more detailed view of the viability and multiplication of bacteria. “For the 3D model, it is an exact measure of how fast the bacteria are growing,” said Guoan Zheng, one of the developers of the new technology, in a press release from the University of Connecticut. “If you just use the 2D model, you just won’t get the exact measure to quantify that growth.”

His team’s system consists of a laser that illuminates the bacterial sample, a microsphere-coated sensor that scatters the light, and a temperature control component that allows researchers to keep the bacteria at the perfect temperature for cultivation. The entire system should fit in a conventional incubator.

After the sample has been imaged at different positions, the researchers reconstruct the resulting diffracted light patterns using an imaging technique called ptychography. The results are more meaningful 3D images for the researchers with regard to bacterial growth. The technique is also fast, allowing the University of Connecticut team to image the bacteria over a period of 15 seconds and follow their growth essentially in real time.

Here is a video by Guoan Zheng showing the tracking of bacteria growth at 15 second intervals and a centimeter field of view with the new sensor. The images shown here are the restored phase profiles of a microcolony:

Study in the journal Biosensors and Bioelectronics: Ptychographic sensor for large-area, lensless microbial monitoring with high spatial-temporal resolution

Flashback: Electrochemical test measures antibiotic resistance

Via: University of Connecticut

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