Cephamycin compounds of the formula (I) (I) wherein R1 represents hydroxyl or sulphooxy and R2 represents sulphooxy together with derivatives thereof including salts, esters, N-protected derivatives and solvates thereof are disclosed. These compounds are of great value as intermediates in the preparation of other cephamycin compounds. The compounds of the invention may be isolated from fermentation broths of strains of the genus Streptomyces which produce the compounds and a new such strain is described. The isolation of the compounds may be achieved by a liquid/liquid or liquid/solid ion-exchange technique, and is preferably achieved by the formation of an ion-pair in a liquid/liquid technique.