The cephalosporins may currently be classified according to their relative susceptibility to beta-lactamases. Cefoxitin, cefamandole, cefatrizine, and cephanone are relatively resistant to the gram-negative beta-lactamases, whereas cephalothin, cefamandole, and cefoxitin are resistant to staphylococcal beta-lactamase. Although the inhibitory activity of cephalothin is representative of that of cephaloridine, cephalexin, cefazolin, cephapirin, cephacetrile, and cephradine, there are significant differences between its activity and that of cefoxitin, cefamandole, and cefatrizine, especially against Enterobacter, Serratia, indole-positive Proteeae, Bacteroides fragilis, and ampicillin-resistant Haemophilus influenzae.