If the bacteria with which someone is infected are antibiotic-resistant, physicians need to know so as soon as possible, so they can take the appropriate action. A simple new system could help, by detecting such resistance in just two hours as opposed to the usual 24.
Ordinarily, in order to see if bacteria have developed a resistance to certain antibiotics, a population of the microbes has to be grown in a Petri dish to which the drugs are then added. It's also possible to perform a genetic analysis of the bacteria, to see if they possess resistance-associated genes.
In either case, it typically takes at least 24 hours to get results. And while there are a few faster methods of "antibiotic sensitivity testing" (AST), they require costly and complex equipment. That's where the new technique comes in.
Developed by scientists from Switzerland's EPFL research institute and Vrije Universiteit Brussel, it utilizes an ordinary optical microscope, a special microscope slide, and either a smartphone or a digital camera.
Users start by placing a drop of bacteria-containing biological fluid on the slide. Tiny microfluidic channels within the slide then draw that fluid onto a minuscule cantilever-like structure. The phone or camera is subsequently used to shoot a video of the bacteria on the structure, through the eyepiece of the microscope.
When the video is analyzed using special software, it can detect tiny vibrations made by each individual bacterium. According to the scientists, these "nanomotions" are produced not just by all living microbes, but by all living organisms.
Needless to say, when an antibiotic is added to the solution on the slide, the bacteria should die and stop vibrating. If they haven't done so within two hours, the software will indicate that they're resistant to that particular drug.
Known as optical nanomotion detection (ONMD), the system has already been used to accurately detect resistance in Escherichia coli, Staphylococcus aureus and Lactobacillus rhamnosus bacteria, when exposed to the antibiotics ampicillin, streptomycin, doxycycline and vancomycin.
A paper on the research, which was led by EPFL's Dr. Sandor Kasas and Vrije Universiteit Brussel's Prof. Ronnie Willaert, was recently published in the journal PNAS.
Source: EPFL