The invention relates to antibacterial compounds of formula Iwherein M is one of the groups MA, MBand MCrepresented belowwherein R1, MA, MBand MCare as defined in the specification; and to salts thereof.本發明係關於式I之抗菌化合物及其鹽類,其中M係下文所代表之基團MA、MB及MC中之一者:其中R1、MA、MB及MC係如說明書中所定義。