The invention relates to novel compounds of high antimicrobial activity of the formula: ##STR1## in which R.sup.1 is amino-substituted-heterocyclic group which may have halogen, protected amino-substituted-heterocyclic group which may have halogen, or a group of the formula: ##STR2## wherein R.sup.3 is lower alkyl,R.sup.2 is carboxy or a protected carboxy group, andA is lower alkylene which may have a substituent selected from the group consisting of amino, a protected amino group, hydroxy, oxo and a group of the formula: .dbd.N.about.OR.sup.4, wherein R.sup.4 is hydrogen, cyclo(lower)alkenyl, lower alkynyl, lower alkenyl, lower alkenyl substituted by carboxy or a protected carboxy group, lower alkyl, or lower alkyl substituted by one or more substituents selected from carboxy, a protected carboxy group, amino, a protected amino group, cyano, phosphono, a protected phosphono group and a heterocyclic group which may have suitable substituents.