Technique combines light-based analytical methods with microfluidic sample processing for pathogen diagnosis

March 14, 2018, Leibniz-Institute of Photonic Technology
The microfluidic chip allows for optical determination of antibiotic resistance patterns. Credit: S. Döring/ Leibniz-IPHT

Scientists of the Leibniz-Institute of Photonic Technologies (Leibniz-IPHT), Center for Sepsis Control and Care at the University Hospital Jena and Friedrich Schiller University have developed a faster and cheaper alternative for pathogen diagnostics. Project manager Prof. Ute Neugebauer says, "We combine light-based analytical methods with microfluidic sample processing. With our Lab-on-a-Chip system, we are able to clearly identify bacterial strains and their resistances in less than three hours."

Standard practices for infectious diagnostics require up to 72 hours for a reliable result. This is due to the fact that the number of pathogens in a sample is generally too small to conduct tests. Analysis is therefore only possible after time-consuming cultivation. During clinical treatment of severe infections like sepsis, time is crucial. Intensive care physicians are confronted with an alarming dilemma: "Far too often, we have to administer broad-spectrum antibiotics blindly, because we can neither analyse pathogen nor potential resistances. Therefore, we use a sledgehammer to crack a nut. A vicious cycle that aides the development of new resistances," explains Prof. Michael Bauer, director of the Clinic of Anesthesiology and Intensive Care at the University Hospital Jena.

The new method out of Jena provides much faster diagnosis as a basis for choosing a reliable therapy. Ute Neugebauer, who works at Leibniz-IPHT and the University Hospital Jena points to tiny electrodes that are fixed on the surface of a stamp-sized chip: "Electric fields secure bacteria in a very small area." Jena's scientists then apply various antibiotics in different concentrations on the trapped bacteria and examine them with Raman spectroscopy. "This means that we irradiate the pathogens with laser light and evaluate the scattered light spectrum," describes Neugebauer the method.

Prof. Jürgen Popp of the Friedrich-Schiller University Jena, says, "After two hours, we can detect distinct changes in the Raman spectra. Out of these, we can derive whether the strain is resistant or sensible. At the same time, we get information on the desired concentration of the antibiotic to constrain bacterial growth. This is an important diagnostic parameter that influences the success of a treatment." The results were published in Analytical Chemistry in February 2018.

The combination of fast, light-based diagnostics and a high automation level reduces the time from sampling to result from 72 hours to only three and a half hours. "Such a fast procedure could revolutionise diagnostics of infectious diseases," says Prof. Bettina Löffler, director of the Institute of Medical Microbiology at the University Hospital Jena. Currently, the researchers are developing a platform for application in hospitals. A more far- reaching aim is to develop a cartridge-based rapid test system that will enable general practitioners to identify resistances quickly.

Explore further: Device may detect urinary tract infections faster

More information: Johanna Kirchhoff et al, Simple Ciprofloxacin Resistance Test and Determination of Minimal Inhibitory Concentration within 2 h Using Raman Spectroscopy, Analytical Chemistry (2017). DOI: 10.1021/acs.analchem.7b03800

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