Compounds of the formula (I), or a pharmaceutically-acceptable salt, or an in-vivo-hydrolysable ester thereof, ##STR00001## wherein --N-HET is, for example, (Ic) or (If) ##STR00002## wherein R1 is (1-4C)alkyl; Q is selected from, for example, Q1 ##STR00003## wherein R.sup.2 and R.sup.3 are independently hydrogen or fluoro; T is selected from a range of groups, for example, ##STR00004## wherein m is 0, 1 or 2; are useful as antibacterial agents; and processes for their manufacture and pharmaceutical compositions containing them are described.