Test for sepsis bacteria's antibiotic resistance

Researchers have developed a test to reveal a pathogen’s resistance to antibiotics using a magnetic field and chemiluminescence.

The test was developed to speed up the diagnostic process for patients with sepsis.

The staphylococcus bacteria can cause life-threatening blood poisoning and is fatal in up to 40% of cases, according to researchers from Empa. When sepsis arises, it is vital that the pathogens are identified as quickly as possible and appropriate antibiotics selected for treatment.

This is particularly crucial for the survival chances of those affected, as Staphylococcus aureus strains can be insensitive to various antibiotics.

“If the bacteria in a blood sample first have to be cultivated for a diagnostic procedure, valuable time is lost,” explained Qun Ren, group leader from Empa’s Biointerfaces lab in St. Gallen.

Ren and her colleague Fei Pan worked with researchers from ETH Zurich to find a way to bypass this lengthy intermediate step.

The team developed a method using magnetic nanoparticles that can bind to staphylococci. The bacteria can thus be specifically detected via a magnetic field. In a next step, the sensitivity to antibiotics is analysed using a chemiluminescence method. If resistant bacteria are in the test tube, the sample emits light. If the germs can be killed with antibiotics, the reaction vessel remains dark.

“All in all, the sepsis test takes around three hours — compared to several days for a classic cultivation of bacterial cultures,” Pan said.

Pseudomonas aeruginosa can cause urinary tract infections which can develop into sepsis. These pathogens are also often resistant to a number of antibiotics.

The magnetic nanoparticle method can be tailored to many different types of bacteria, similar to a modular system. In this way, Empa researchers were able to develop a rapid ‘sepsis sensor’ based on magnetic nanoparticles. In samples containing artificial urine, the method reliably identified the bacterial species and determined possible resistance to antibiotics via a chemiluminescence reaction.

Image caption: Magnetic nanoparticles (red) bind specifically to the spherical bacteria (yellow) which are about 1 µm in size (electron microscopy digitally coloured). Image supplied by Empa.

So far, the researchers have evaluated their magnetic nanoparticle kit for sepsis and urinary tract infections using laboratory samples.

“In a next step, we would like to validate the sepsis tests together with our clinical partners by evaluating patient samples,” Ren said.

Top image credit: iStock.com/Dr_Microbe