In vitro and in vivo antibacterial activities of S-4661, a new carbapenem

Abstract

The in vitro and in vivo antibacterial activities of S-4661, a new 1β- methylcarbapenem, were compared with those of imipenem, meropenem, biapenem, cefpirome, and ceftazidime. The activity of S-4661 against methicillin- susceptible staphylococci and streptococci was comparable to that of imipenem, with an MIC at which 90% of the strains tested were inhibited (MIC90) equal to 0.5 μg/ml or less. S-4661 was highly active against members of the family Enterobacteriaceae, Haemophilus influenzae, and Moraxella catarrhalis, with MIC90s ranging from 0.032 to 0.5 μg/ml. Against imipenem-resistant Pseudomonas aeruginosa, S-4661 was the most active among test agents (MIC90, 8 μg/ml). Furthermore, S-4661 displayed a high degree of activity against many ceftazidime-, ciprofloxacin-, and gentamicin- resistant isolates of P. aeruginosa. The in vivo efficacy of S-4661 against experimentally induced infections in mice caused by gram-positive and gram- negative bacteria, including penicillin-resistant Streptococcus pneumoniae and drug-resistant P. aeruginosa, reflected its potent in vitro activity and high levels in plasma in mice. We conclude that S-4661 is a promising new carbapenem for the treatment of infections caused by gram-positive and - negative bacteria, including penicillin-resistant S. pneumoniae and drug- resistant P. aeruginosa.