RESUMO
Ceftriaxon (Ro 13-9904) is a new cephalosporin, whose structure resembles cefotaxime. This study compares the minimal inhibitory concentrations (MIC-s) of Ceftriaxon, cefoperazone, cefotaxime, lamoxactam and gentamicin against 622 isolates of various Enterobacteriaceae, non-fermenters and Aeromonas hydrophila. Furthermore the minimal bactericidal concentrations (MBC-s) were determined for some organism; additionally destruction of beta-lactamantibiotics in the presence of beta-lactamases was studied by a bioassay technique. The in vitro activity of Ceftriaxon against gramnegative bacteria was found very similar to that of cefotaxime. The susceptibility of Enterobacter sp. to the three cephalosporines was exceeded by lamoxactam while cefoperazone was the most active beta-lactam-antibiotic against Pseudomonas. Lactamases, which inactivated cefotaxime also destroyed Ceftriaxon in a greater extend. No hydrolysis of lamoxactam and cefoperazone occurred by nearly all bacterial extracts tested.