It is produced by the strain of Semisynthetic fourth generation cephalosporin for injection. Cefoselis, a new parenteral cephalosporin, was active against clinical isolates of both gram-positive and gram-negative aerobic bacteria. The activity of Cefoselis was similar to that of cefpirome and cefepime and generally superior to that of ceftazidime. Cefoselis showed potent antibacterial activity against Hemophilus influenzae and Moraxella catarrhalis. Cefoselis was highly active against MSSA and MSCNS. Cefoselis was poor in the activity against MRSA, MRCNS, PRSP and Enterococcus faecalis, and had no activity for Enterococcus faecium.