A crystalline form of crystalline (R)-3-(4-(2-(2-methyltetrazol-5-yl)-pyridin-5-yl)-3-fluorophenyl)-5-hydroxymethyl oxazolidin-2-one dihydrogen phosphate, methods of making the crystalline form and pharmaceutical compositions comprising the crystalline form are useful antibiotics. Further, the derivatives of the present invention may exert potent antibacterial activity versus various human and animal pathogens, including Gram-positive bacteria such as Staphylococi, Enterococci and Streptococi, anaerobic microorganisms such as Bacteroides and Clostridia, and acid-resistant microorganisms such as Mycobacterium tuberculosis and Mycobacterium avium. Accordingly, the compositions comprising the crystalline form may be used in antibiotics.