Compounds represented by the following formula (I), that is, cephem derivatives having substituted or unsubstituted imidazo[5,1-b]thiazolium-6-yl as a substituent at the 3-position of the cephem ring: ##STR1## wherein X represents CH or N, R.sup.1 represents H, alkyl, alkenyl or the like, and R.sup.2, R.sup.3, R.sup.4 and R.sup.5 represent H, alkyl, carbamoyl, amino or the like. The above compounds have excellent antibacterial activity, and useful as medicines for the treatment of various infectious diseases caused by bacteria.
A compound represented by general formula (I), i.e., a cephem derivative having an (un)substituted imidazo-[5,1-b]thiazolium-6-yl group at the 3-position of the ring, wherein X represents CH or N; R1 represents H, alkyl, alkenyl, etc.; and R2, R3, R4 and R5 represent each H, alkyl, carbamoyl, amino, etc. This compound has an excellent antibacterial activity and is useful as a remedy for various types of microbism.