Inhibits bacterial cell wall synthesis by binding to one or more of the penicillin-binding proteins. Usually bactericidal. Less active against Enterobacteriaceae than some other third-generation cephalosporins. Active in vitro and in clinical infections against Gram-positive aerobic bacteria, such as Streptococcus pneumoniae and Streptococcus pyogenes (group A β-hemolytic streptococci), active in vitro against S. agalactiae (group B streptococci) and groups C, F, and G streptococci. Most staphylococci, enterococci, and Listeria monocytogenes are resistant. Oxacillin-resistant S. aureus (methicillin-resistant S. aureus) are resistant. Active in vitro and in clinical infections against Gram-negative aerobic bacteria such as Neisseria gonorrhoeae, Haemophilus influenzae (including β-lactamase-producing strains), Moraxella catarrhalis (including β-lactamase-producing strains), Escherichia coli, and Proteus mirabilis. Also active in vitro against H. parainfluenzae, Klebsiella, Pasteurella multocida, P. vulgaris, Providencia, Salmonella, Shigella, and Serratia. Most Enterobacter and Pseudomonas are resistant. Inactive against most anaerobic bacteria, chlamydia, fungi, and viruses.