Ro 17-2301: in vitro comparison with aztreonam, imipenem, ceftazidime, cefotaxime and netilmicin

The in vitro activity of the novel monobactam antibiotic, Ro 17-2301 has been compared with those of aztreonam, imipenem, ceftazidime, cefotaxime and netilmicin. A total of 438 clinical isolates of aerobic gram-negative rods were employed and an agar dilution method was used for measurement of MIC. Ro 17-2301 was highly active against a wide variety of Enterobacteriaceae species (MIC range less than or equal to 0.03-8, MIC50 less than or equal to 0.03, MIC90 0.06 mg/l). The activity of aztreonam parallelled that of Ro 17-2301 although the latter seemed to have more uniformly high activity against Klebsiella sp. The other agents showed generally high activity against Enterobacteriaceae except netilmicin against Providencia stuartii (MIC50 4, MIC90 greater than or equal to 16 mg/l). Activity against Pseudomonas aeruginosa. was more variable. Ro 17-2301 and aztreonam were moderately active (MIC50 2, MIC90 8 and 16 mg/l, respectively). Imipenem was the most active agent against Acinetobacter, whereas Ro 17-2301 was moderately active. In conclusion, Ro 17-2301 shows impressive activity against Enterobacteriaceae and moderate activity against Acinetobacter and P. aeruginosa. Ro 17-2301 may well prove to be a useful agent in the treatment of gram-negative infections.