In vitro studies of S-25930 and S-25932, two new 4-quinolones.

The in vitro activity of S-25930 and S-25932 was compared with that of ciprofloxacin, norfloxacin and nalidixic acid against 740 clinical isolates. The data indicate that S-25930 was more active against Enterobacteriaceae than S-25932 and the latter was more active against gram-positive species. A study of clinical isolates resistant to chemically non-related classes of antibiotics revealed no cross-resistance. Nalidixic acid resistant Enterobacteriaceae showed an eight-fold decrease in susceptibility to the new agents. The killing kinetics of both compounds were good, S-25932 having an optimal bactericidal effect at a concentration of 0.5 mg/l. The data suggests that both agents are effective broad spectrum antibiotics.