The reality and intensity of antibiotic resistance in pathogenic bacteria calls for the rapid development of new antimicrobial drugs. In bacteria, trans-translation is the primary quality control mechanism for rescuing ribosomes arrested during translation. Because transtranslation is absent in eukaryotes but necessary to avoid ribosomal stalling and therefore essential for bacterial survival, it is a promising target either for novel antibiotics or for improving the activities of the protein synthesis inhibitors already in use. Oxadiazole derivatives display strong bactericidal activity against a large number of bacteria, but their effects on trans-translation were recently questioned. In this work, a series of new 1,3,4oxadiazole derivatives and analogs were synthesized and assessed for their efficiency as antimicrobial agents against a wide range of gram-positive and gram-negative pathogenic strains. Despite the strong antimicrobial activity observed in these molecules, it turns out that they do not target trans-translation in vivo, but they definitely act on various other cellular pathways. This work was supported by the Direction Générale de l'Armement (#ANR-14-ASTR-0001) and the Agence Nationale pour la Recherche under the frame of the Joint JPI-EC-AMR Project named "Ribotarget-Development of novel ribosome-targeting antibiotics" (SNF No.

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