Fig. 1: Nitroxoline is active beyond UTI pathogens, including intracellular bacteria, and exerts bactericidal activity.

a Nitroxoline structure. b Overlap between Gram-negative bacterial genera or species tested with three orthogonal susceptibility testing methods in this study and according to EUCAST¹⁸. All seven EUCAST-specific entries are genera for which species resolution is missing. The number of overlapping species/genera between EUCAST and our methods is shown as intersection size, whereas the number of genera/species assessed by each approach is shown as set size. c Nitroxoline is active against several Gram-negative bacterial species. MICs were determined against 30 bacterial species in broth microdilution. The total number of strains tested is indicated next to species, ordered by phylogeny according to GTDB⁷⁷ (Methods). The clinical breakpoint for E. coli (16 µg/ml) is indicated (black line). MIC₅₀ values are framed in black and listed in the Source Data Fig. 1c together with MIC₉₀ values. d Nitroxoline is active against intracellular S. Typhi. Intracellular bacterial counts were assessed with the gentamicin protection assay in two S. Typhi clinical isolates (Methods, Supplementary Data 2). Cell counts were determined before and after treatment with nitroxoline (5 µg/ml) or solvent control (DMSO) at 7 h p.i. (MOI 100). Mean and standard error are shown across four independent experiments. ns p > 0.05; *p = 0.022; **p = 0.003 (two-sided Welch’s t-test). e Nitroxoline is bactericidal against A. baumannii ATCC 19606^T. Mean and standard deviation across at least three biological replicates are shown for each condition. f Nitroxoline induces lysis in A. baumannii ATCC 19606^T. White arrowheads mark the release of cytoplasmic material and loss of the pericellular halo. Representative images of phase-contrast videos were acquired after 8 µg/ml nitroxoline treatment (4x MIC, Methods, Supplementary Movie 1). The scale bar denotes 5 µm. Source data are provided as a Source Data file.