There are provided compounds of formula ##STR1## wherein R is hydrogen atom or C.sub.1 -C.sub.3 alkyl group optionally substituted from halogen atom or hydroxy group optionally protected, and Q.sup.(+) represents a group ##STR2## wherein R.sub.1, R.sub.2 and R.sub.3 are each either: (i) optionally substituted alkyl, aralkyl or aryl radical or(ii) R.sub.1 is as defined above under (i) and R.sub.2, R.sub.3, taken together, represent an optionally substituted or fused heterocyclic radical or(iii) R.sub.1, R.sub.2, R.sub.3, taken together, represent an optionally substituted azonia-bicyclo or tricyclo radical or(iv) R.sub.1, R.sub.2, R.sub.3, taken together, represent an optionally substituted fused pyridinium radical or(v) R.sub.1, R.sub.2, R.sub.3, taken together, represent an optionally substituted pyrazimium, pyrazolium or pyridazinium radical, and the pharmaceutically or veterinarily acceptable salts thereof.A method of preparation is also provided.The compounds show high antibacterial activity.