Currently, the diagnosis of bacterial infections is usually based on growing bacteria in microbiological cultures in the laboratory, which is labor-intensive and time-consuming (1-4 days). For some bacteria, such as the slow-growing tuberculosis bacterium Mycobacterium tuberculosis, this can take even longer. This means that antibiotic treatment is usually started before the laboratory results are received and the choice of medication is therefore based on a guess. This is one of the causes of the increasing development of antibiotic resistance: As the bacteria thus come into contact with “inappropriate” antibiotics, they can subsequently develop resistance to these agents.
Researchers are therefore very interested in speeding up the diagnostic process. There are a number of approaches to automate the process. While these efforts are promising, they still rely on microbiological culture (1-2 days) to enrich the bacteria for appropriate detection.
The ideal diagnostic test should identify the specific pathogen much more quickly and indicate an appropriate therapy based on the antibiotic resistance pattern. This is particularly important for diseases such as pneumonia and blood poisoning (sepsis), which can be caused by many different pathogens (viruses, bacteria or fungi) and in which antibiotic resistance is particularly common.

Peptide nanosensor
Protein building blocks (peptides) that react specifically to a germ in a sample can be coupled with magnetic nanoparticles. Empa researchers are working on these peptide nanosensors to enable the specific detection and enrichment of pathogens for rapid detection. In addition, some volatile organic compounds are being investigated as sensor candidates that are also specific for certain bacteria.
Ultrafast Determination of Antimicrobial Resistant Staphylococcus aureus Specifically Captured by Functionalized Magnetic Nanoclusters
Specific capture of Pseudomonas aeruginosa for rapid detection of antimicrobial resistance in urinary tract infections
A rapid and specific antimicrobial resistance detection of Escherichia coli via magnetic nanoclusters

Biosensors
 Certain parameters in the blood or in wound exudate, so-called biomarkers, can indicate problems with wound healing and bacterial infections. Empa researchers are developing optical methods with bio-responsive materials to detect such biomarkers (e.g., pH, glucose, proteinases).
Lab-on-a-Fiber Wearable Multi-Sensor for Monitoring Wound Healing 

Bacterial Sensors

Empa researchers are also working on the indirect detection of specific bacteria via reaction of functionalised nanoparticles with enzymes secreted by bacteria. In one example, nanoparticles were developed that are sensitive to the enzyme urease, produced by bacteria causing pneumonia. The sensor fluoresces in the presence of this bacteria within a few hours, providing a fast, robust, sensitive, and selective detection method for Klebsiella pneumoniae and Enterobacter cloacae.
Fluorescent Probe for the pH-Independent Rapid and Sensitive Direct Detection of Urease-Producing Bacteria