Antibacterial Activity of a New Cephalosporin, Cefotaxime

The antibacterial activity of a new cephalosporin derivative, cefotaxime (HR 756), was determined. The antibiotic was active at low concentrations against R⁺ and R^- strains of Gram negative bacteria, including two out of three strains of Serratia marcescens. In general higher concentrations were needed to inhibit growth of Pseudomonas aeruginosa. Low concentrations induced elongation of cells in circumstances conducive to active growth; higher concentrations caused lysis in some strains. Cefotaxime was more stable than cephaloridine, cephalothin, cephalexin, cefoxitin and cefuroxime to various β-lactamases.