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Cephalosporin antibiotics of general formula Wherein R represents a 3-or 4-carbamoyl group or a hydrogen atom) and non-toxic salts and non-toxic metabolically labile esters thereof, the compounds exhibit broad spectrum antibiotic activity and have high activity against both Gram-positive and Gram-negative organisms, including many B-lactamase producing strains, especially preferred are those compounds in which R is hydrogen.