The present invention provides a novel compound which has a broad antibacterial spectrum and particularly exhibits a high antibacterial activity on β-lactamase-producing gram-negative bacteria. Specifically provided are: a compound represented by formula (I)
wherein the meaning of each symbol is as defined in the description, an amino-group-protected form of a type of the compound which has the amino group on a ring in a position-7 side chain, or a pharmaceutically acceptable salt of the compound or the amino-group-protected form; and a pharmaceutical composition containing the compound, the amino-group-protected form or the pharmaceutically acceptable salt.