A new cephalosporin. SCE-963: 7-[2-(2-aminothiazol-4-yl)-acetamido]-3-[[[1-(2-dimethylaminoethyl)-1H-tetrazol-5-yl]-thio]methyl]ceph-3-em-4-carboxylic acid. Chemistry and structure-activity relationships.:CHEMISTRY AND STRUCTURE-ACTIVITY RELATIONSHIPS