In vitro activity of WIN 49375 compared with those of other antibiotics in isolates from cancer patients.

The activity of WIN 49375 [6-fluoro-1, 4-dihydro-1-(methylamino)-7-(4-methyl-1-piperazinyl)-4-oxo-3- quinolinecarboxylic acid], a new synthetic quinolone, was tested in vitro against 587 clinical isolates. The MICs for 90% of isolates of Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae were 0.20, 1.56, and 0.39 microgram/ml, respectively. The MICs for 90% of isolates of Pseudomonas aeruginosa and Serratia marcescens were both 3.12 micrograms/ml. WIN 49375 was minimally active against gram-positive cocci. Its in vitro activity suggests that it may be useful for the treatment of gram-negative bacillary infections.