Abstract: New cephalosporin derivatives, of the formula: ##STR1## in which R.sub.1 is a heterocyclic, phenyl, p-hydroxyphenyl, phenoxy or dichlorophenylthio radical and R.sub.2 is a hydrogen atom, or R.sub.1 is phenyl or p-hydroxyphenyl and R.sub.2 is an amino radical, R.sub.3 is hydrogen, phenyl, substituted phenyl, alkylthio or substituted amino or a radical of the structure --A--R'.sub.3, which A is --CH.sub.2 --, --NH-- or --NHCO-- and R'.sub.3 is a substituted pyridinio radical, R is a carboxyl radical or a carboxylato radical if R.sub.3 is a --AR'.sub.3 radical and X is a sulphur or oxygen atom, the said alkyl moieties or radicals containing 1 to 4 carbon atoms each in their D, L and D,L forms, where these exist, and their salts are narrow-spectrum anti-bacterial agents which are active against gram-positive bacteria.