A cephalosporin derivative of the formula I: ##STR1## in which X is S, O, CH.sub.2 or SO, ##STR2## represents one of C-7 acyl groups known in the cephalosporin art, R3 is hydrogen or methoxy, R4 is hydrogen, optionally substituted alkyl or allyl, and R5 is an aromatic heterocyclic ring system which is linked via carbon, and which contains a quaternized nitrogen atom.
                            一种
头孢菌素衍
生物,其
化学式为I:##STR1## 其中X是S、O、CH.sub.2或SO,##STR2##代表
头孢菌素艺术中已知的C-7酰基之一,R3是氢或甲氧基,R4是氢,可选地被取代的烷基或烯丙基,R5是一种芳香杂环环系统,通过碳链连接,并且含有一个季
铵化的氮原子。