Transgene expression of green fluorescent protein (GFP) has facilitated the spatiotemporal investigation of host-pathogen interactions; however, introduction of the GFP gene remains challenging in drug-resistant bacteria. Herein, we report a novel far-red fluorescent nucleic acid stain, 6-TramTO-3, which efficiently labels bacteria through a DNA binding mode without affecting growth and viability. Exemplarily, we stained Klebsiella pneumoniae, a major threat to hospitalized patients, and deciphered divergent interaction strategies of antibiotic-resistant and antibiotic-sensitive Klebsiella strains with immune cells. 6-TramTO-3 constitutes an off-the-shelf reagent for real-time analysis of bacterial infection, including strains for which the use of genetically encoded reporters is not feasible. Eventually, our approach may aid the development of strategies to combat a major worldwide health threat: multidrug-resistant bacteria.
Keywords: DNA recognition; antibiotics; far-red cyanine dyes; fluorescence-activated cell sorting; multidrug-resistant bacteria.
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