Cephem compounds, pharmaceutically acceptable salts thereof, and methods of using same, wherein the compound has a bicyclic nitrogen-containing aromatic heterocyclic ring as the quaternary ammoniomethyl group at the 3-position and one or both of a terminal amidine residue (substituted or unsubstituted) attached to an aryl or a 5- or 6-membered heteroaryl group (substituted or unsubstituted) which is further attached through a spacer to the free N-atom of the quaternary nitrogen-containing bicyclic ring at the 3-side chain, or a terminal guanidine residue attached to an aryl or a 5- or 6-membered heteroaryl group (substituted or unsubstituted) which is further attached through a spacer to the free N-atom of the quaternary nitrogen-containing bicyclic ring at the 3-side chain.