Disclosed is a cephem compound represented by formula (I) [wherein X represents N, CH, or C-Cl； T represents S, or the like； A and G independently represent a lower alkylene, or the like； B represents a single bond, or the like； D represents a single bond, -NR-CO, -CO-NR-, -NR-CO-NR-, or the like； E represents a lower alkylene which may be substituted； F represents a single bond, or a phenylene which may be substituted； R, R, Rand Rindependently represent a hydrogen, a halogen, a nitrile, or -OR； Rrepresents a hydrogen, or the like； and a group represented by formula (II) represents a saturated or unsaturated monocyclic or ring-fused quaternary ammonium group which has at least one N atom and may be substituted, wherein the dashed line represents a bond in the ring], an ester of the cephem compound, a protected product of the cephem compound in which an amino group located on the ring in the chain on the 7-position side is protected, a pharmaceutically acceptable salt of the cephem compound, the ester or the protected product, or a solvate of the cephem compound, the ester, the protected product or the pharmaceutically acceptable salt, which has a broad antibacterial spectrum and particularly has a potent antibacterial activity against &bgr；-lactamase-producing Gram-negative bacteria. Also disclosed is a pharmaceutical composition comprising the cephem compound, the ester, the protected product, the pharmaceutically acceptable salt or the solvate.В данном изобретении предложены следующие соединения цефема, которые имеют широкий спектр противомикробной активности и отличаются высокой противомикробной активностью против грамотрицательных бактерий, продуцирующих бета-лактамазу:соединение формулы I, (I)гдеX представляет собой N, CH или С-Cl；Т представляет собой S или т.п.；А и G представляют собой низший алкилен или т.п.；В представляет собой простую связь или т.п.；D представляет собой простую связь -NR-, -CO-, -CO-NR-, -NR-CO-, -NR-CO-NR- или т.п.；Е представляет собой н
