Intracellular activity of tosufloxacin (T-3262) against Salmonella enteritidis and ability to penetrate into tissue culture cells of human origin.

The intracellular antimicrobial activity of tosulfoxacin was tested against Salmonella enteritidis C-32 by using human lung fibroid WI-38 cells and was compared with those of ofloxacin and norfloxacin. The intracellular antimicrobial activities of these drugs were evaluated by determining the numbers of viable organisms remaining within cells after treatment with various drug concentrations. At 0.2 and 0.78 microgram/ml, tosufloxacin suppressed intracellular multiplication of S. enteritidis C-32 more effectively than ofloxacin and norfloxacin did. The ability of tosufloxacin to penetrate into WI-38 cells was also determined by the velocity gradient method. The ratio of the intracellular concentration to the extracellular concentration of tosufloxacin was 1.7- and 2.6-fold higher than those of ofloxacin and norfloxacin, respectively. The results indicate that the potent intracellular bactericidal activity of tosufloxacin may be due not only to its high in vitro activity but also to its ability to penetrate into cells at a high level.