A cephalosporin antibiotic that is active against most Gram-positive cocci, including penicillinase-producing Staphylococci, and against Gram-negative bacteria such as N. gonorrhoeae, E. coli, K. pneumonia, Salmonellae, Shigella, and some strains of H. influenza; specifically inactivates PBP3, which is essential for bacterial cell wall synthesis.