an antibiotic with activity due to the 7-aminocephalosporanic acid portion of the cephalosporanic acid molecule; it is effective against gram-positive and gram-negative bacteria, but is less potent than cephalosporin N. Addition of side chains produced semisynthetic broad spectrum antibiotics with greater antibacterial activity than that of cephalosporin C; the antibiotic activity is due to interference with bacterial cell-wall synthesis.