Pharmaceutical compositions comprising nadifloxacin, i. e. S-(-)-9- fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yl)-5-methyl-l-oxo-lH,5H- benzo[i,j] quinolizine-2-carboxylic acid L-arginine salt, and their use in treatment, control or prevention of bacterial infections is disclosed.