Cephalosporin antibiotics and pharmaceutical composition comprising the same

Novel chphalosporin compounds of formula (I), wherein: R1 is a hydrogen or an amino protecting group; R2 and R3 are, independently, a hydrogen or a hydroxy protecting group, or form together a cyclic diol protecting group; R4 and R5 are, independently, a hydrogen or a carboxyl protecting group; X and Y are a nitrogen and a carbon atom, respectively, or a carbon and a nitrogen atom, respectively; R6 and R7 are, independently, a hydrogen or an amino, substituted amino, hydroxy, alkoxy, C1-4 alkyl, carboxyl or alkoxy carbonyl group, or jointly form a C3-7 cycloalkyl group together with the carbon to which they are attached, when X and Y are a nitrogen and a carbon, respectively, or R7 is a hydrogen or an amino group when X and Y are a carbon and a nitrogen, respectively; and Q is =CH- or =N-, or pharmaceutically acceptable non-toxic salts, physiologically hydrolyzable esters, hydrates and solvates and isomers thereof, and isomers thereof possess potent and broad antibacterial activities.