5H-isothiazolo[4,5-c]pyridine-3,4-dione or 5H-pyrazolo[4,3-c]pyridin-3,4-dione as antibacterial compounds

This invention relates to antibacterial drug compounds of formula (I) containing a fused isothiazolinone or pyrazolone ring and related compounds. It also relates to pharmaceutical formulations of antibacterial drug compounds. It also relates to uses of the derivatives in treating bacterial infections and in methods of treating bacterial infections. Many of the antibacterial drug compounds contain a isothiazolinone or pyrazolone ring fused to a pyridone ring. The compounds have broad spectrum antibacterial activity but are particularly effective against Gram negative strains. wherein X is selected from S, SO, SO2, O and NR4;