Group of cephalosporin antibiotics capable of killing gram-positive cocci such as Staphylococcus aureus, streptococci, and some aerobic gram-negative rods. These agents are commonly used to treat skin and soft tissue infections, uncomplicated respiratory tract infections, and urinary tract infections. Examples of first generation cephalosporins are cephalothin, cephaloridine, cephapirin, cefazolin, cephradine, cephalexin, and cefadroxil.