A β-lactam antibiotic; inhibits the growth of clinical isolates of Streptococci (MICs = 0.004-0.008 mg/l) and C. difficile (MICs = 1 to >256 mg/l); inhibits growth of S. aureus in vitro (MIC = 0.016 mg/l) and in vivo in a thigh model of infection in mice; inhibits the growth of S. pyogenes in mice following one or two dose therapy (CD50s = 0.207 and 0.031 mg, respectively); prevents experimental acute otitis media in rats when administered at 100 mg/kg per day (p.o.) prior to infection by pneumococci