Antibiotic resistance is a major global issue requiring coordinated action from researchers, industry, and healthcare systems. Affecting human, animal, and environmental health, it is now addressed through the “One Health” approach. The World Health Organization has identified priority pathogens capable of developing multidrug resistance and emphasizes the urgent need for new treatments, regulatory strategies, and diagnostic tools.
Rapid and accessible detection methods are essential, particularly for low-resource settings. Currently, the antibiogram remains the standard method but requires 48–72 hours, limiting timely decision-making. Faster alternatives are therefore needed.
Among resistance mechanisms, efflux pumps—identified since the 1980s—play a key role. These systems expel toxic compounds, including antibiotics and antiseptics, preventing them from reaching effective intracellular concentrations. Their overproduction is frequently observed in multidrug-resistant bacteria, making them an important target for detection. Identifying strains with hyperactive efflux can improve therapeutic choices and help limit the spread of resistance.
Based on the ability of efflux pumps to transport diverse molecules, we investigated fluorescent phenazinium derivatives as potential substrates. Compounds synthesized by Olivier Siri’s team were evaluated by comparing their accumulation in bacterial strains with varying efflux activity. This approach led to the identification of a molecule capable of distinguishing between normal, inactive, and overproducing efflux systems.
After optimization, the method was tested on around 100 Staphylococcus aureus isolates previously characterized by conventional techniques, achieving over 80% accuracy. It was also successfully applied to other Gram-positive bacteria. With slight modifications, the method was extended to Gram-negative species such as Escherichia coli and Klebsiella, with further validation ongoing.
This test is rapid, cost-effective, and easy to perform, delivering results within hours and saving up to 48 hours compared to standard methods. It has been patented and is currently marketed as Colorflux®.
