The invention relates to the compounds (I) and their acids and bases salts: wherein: Formula (I) the dotted line indicates a double bond; X is N or C—R1 and Y is N or C—R2, X and Y not being simultaneously N; A is selected from the group consisting of phenyl, naphthyl and (5-11) membered monocyclic or bicyclic unsaturated cycle or heterocycle possibly substituted as defined in the application, and A can also comprise either a further (4-7) membered heterocycle, said heterocycle being a monocycle, fused, saturated or unsaturated, the polycyclic system then comprising up to 14 members and up to 5 heteroatoms selected from N, O and S; B is selected from the group of substituents as defined in the application, or B is a 4 or (6-10) membered mono or bicyclic saturated or unsaturated heterocycle containing 1-3 heteroatoms selected from N, O and S, linked by a carbon atom, and possibly substituted as defined in the application; R1 is Hydrogen or a substituent as defined in the application; R2 is Hydrogen or Halogen; their preparation, their use in the antibacterial prevention and therapy, alone or in association with antibacterials, antivirulence agents or drugs reinforcing the host innate immunity, and pharmaceutical compositions and associations containing them.