Combination effect of SCE-2787 and cefepime with aminoglycosides on nosocomial gram-negative bacteria

The in vitro activity of cefepime and SCE-2787, two new parenteral cephalosporins, and the combination effect with tobramycin and gentamicin against nosocomial gram-negative rods was studied using checkerboard agar dilution technique. Cefepime showed excellent in-vitro activity against Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens and Proteus vulgaris (MIC90 0.03-0.125 mg/l) and good to moderate activity against Acinetobacter anitratus, Pseudomonas aeruginosa and Pseudomonas cepacia (MIC90 4-16 mg/l). SCE-2787 had an excellent activity against Citrobacter spp. (MIC90 0.125 mg/l) and a very good activity against A. anitratus, P. aeruginosa and P. vulgaris (MIC90 1-2 mg/l). Pseudomonas maltophilia was not inhibited at therapeutically achievable concentrations (MIC90 64 mg/l). On average, 14-28% of the strains were inhibited by synergistic SCE-2787 aminoglycoside-combinations, whereas only 8.6% were inhibited by a synergistic effect of the combination with cefepime and gentamicin. No antagonism occurred with any of the combinations.