In vitro and in vivo antibacterial activities of a new injectable carbapenem, S-4661, against gynaecological pathogens

Carbapenems are often used to treat infections in obstetrics and gynaecolog y because of their activity against anaerobes, S-4661, a new injectable car bapenem antibiotic, has favourable pharmacokinetic properties and is not hy drolysed by dehydropeptidase I. We investigated the in vitro and in vivo an tibacterial activities of S-4661 against strains of Streptococcus agalactia e, Escherichia coli, Peptostreptococcus magnus, Bacteroides fragilis and Pr evotella bivia, which are major pathogens in the fields of obstetrics and g ynaecology. The MIC50 and MIC90 of S-4661 for these strains were 0.25 and 1 mg/L, respectively, The in vivo efficacy of S-4661 was evaluated in a rat model of intrauterine infection, namely pyometra caused by E. coli and S. f ragilis. The accumulation of neutrophils in the uterus in the S-4661-treate d group was less marked and the number of bacteria significantly lower than those in the untreated group. These results suggest that S-4661 may be use ful for treating polymicrobial infections in the fields of obstetrics and g ynaecology.