A compound of formula (I) wherein R and R.sub.2 together with the nitrogen atom to which they are attached form pyrrolidinyl or piperidinyl, R.sub.1 is a group of formula (II) R.sub.3 and R'.sub.3 are hydrogen, deuterium or halogen, R.sub.4, R.sub.5 and R.sub.10 are independently of each other hydrogen or alkyl, R.sub.6, R.sub.7 and R.sub.8 are hydrogen or deuterium; R.sub.9 is amino, alkyl, aryl, heterocyclyl or mercapto; and, if X is oxygen, R.sub.9 is additionally hydrogen; R'.sub.10 is alkyl, X is sulphur, oxygen, NR.sub.10, or N+(R'.sub.10).sub.2; Y is sulphur or oxygen, and m is 0, 1 or 2; with the proviso that, when R and R.sub.2 together with the nitrogen atom to which they are attached form piperidinyl, m is O, Y is S and Y is attached in position 3 of said piperidine ring, that group of formula (I) which is attached to the piperidine ring via the residue Y is either in the (S)-configuration or in the (R)-configuration, preferably in the (S) -configuration which is e.g. useful as antimicrobial, antibacterial.