Unlocking the Gates: A Novel Diagnostic Molecule for Quantifying Efflux Levels in Gram-Positive Bacteria

Efflux-mediated antibiotic resistance poses a significant global threat, affecting diverse bacterial species. Clinicians recognize the danger of efflux mechanisms during antibiotic treatment, yet precise diagnostic tools remain unavailable. The antibiogram currently infers abnormal efflux pump activity in clinical isolates, which is subsequently confirmed through transcriptomic or genomic analysis. This study harnesses the colorimetric, fluorescence, and solubility properties of phenazinium derivatives to develop a rapid protocol for detecting bacterial efflux. Among several synthesized phenazinium compounds, the compound demonstrating differential MIC in Staphylococcus efflux mutants and exhibiting appropriate physicochemical properties is selected. A diagnostic protocol is developed using the selected compound to assess efflux levels, categorized as no, weak, or strong, through colorimetry and spectroscopy techniques. Testing on Gram-positive efflux mutants and clinical Staphylococcus isolates further validates the approach. In-silico docking analysis confirms the interaction between the chosen compound and the NorA efflux pump in S. aureus. Flow cytometry is employed to re-evaluate the detection assays. The developed molecule and protocol represent the first known method to evaluate efflux levels in any Gram-positive species through a streamlined and user-friendly process. This pioneering test significantly advances the epidemiological analysis of efflux mechanisms and enables more informed therapeutic decision-making, leading to more effective treatment.