3d images

New technique generates 3D images of bacteria for antibiotic susceptibility testing

Researchers at the University of Connecticut have developed a highly sensitive imaging sensor capable of quickly and accurately monitoring bacterial growth. The technique involves shining laser light through a bacterial sample and taking images at multiple orientations, before reconstructing the diffracted light patterns, to produce a 3D image of the bacterial colony. These 3D images provide significant details about the growth and characteristics of bacteria, and could be very useful in quickly identifying the most effective antibiotics to kill them.

Determining antibiotic susceptibility is a laborious process. A bacterial sample that has been isolated from a patient will typically be cultured on a nutrient medium, such as agar. Once there are enough bacteria present, which can take several days, lab techs will then start exposing them to different antibiotics. Only then can they assess whether the bacteria are sensitive to certain drugs.

It may be too long to wait for someone with a dangerous infection. As such, the development of faster antibiotic susceptibility testing is an active area of ​​research. This latest technique relies on imaging bacteria in 3D to provide more information than conventional 2D images. For example, if a bacterial colony grew upwards, but not outwards, conventional imaging techniques would not readily reveal this, meaning lab technicians would assume that the colony was not growing at all. .

Conversely, this new technique will reveal such growth, providing more accurate insight into bacterial viability and proliferation. “For the 3D model, it is an accurate measurement of the growth rate of bacteria,” Guoan Zheng, one of the developers of the new technology, said in a press release from the University of Connecticut. . “If you just use the 2D model, it just doesn’t give you the precise metric to quantify that growth.”

His team’s system consists of a laser to illuminate the bacterial sample, a sensor coated with microbeads that scatter the light, and a temperature control component that allows researchers to hold the bacteria at the temperature ideal for cultivation. The whole system should fit in a conventional incubator.

After imaging the sample at different positions, the researchers reconstructed the resulting diffracted light patterns using an imaging technique called ptychography. This results in more informative 3D images for researchers in terms of bacterial growth. The technique is also fast, allowing the University of Connecticut team to image bacteria over a 15-second period, essentially tracking their growth in real time.

Here’s a video by Guoan Zheng showing bacterial growth tracking at 15-second intervals and centimeter-scale field-of-view using the new sensor. The images presented here are the phase profiles recovered from a micro-colony:

Study in the journal Biosensors and bioelectronics: Ptychographic sensor for large-scale lensless microbial monitoring with high spatio-temporal resolution

Flashback: an electrochemical test measures antibiotic resistance

Via: University of Connecticut