The increasing diffusion of antimicrobial resistance represents one of the major public health problems worldwide. In the last years, novel antimicrobial molecules have been developed to contrast the emergence of antimicrobial resistance and to provide a valuable therapeutic options against multi drug-resistant (MDR) GNB microorganisms. A new siderophore cephalosporin, Cefiderocol, represents a novel valuable antimicrobial drug for the treatment of infections caused by MDR-GNB. The mechanism of cefiderocol to penetrate trough the outer membrane of bacterial cell with a particular mechanism defined at “Trojan horse” render this molecule unique and immune against the different strategies adopted by GNB to counteract the activity of antimicrobial molecules. The broad spectrum of activity against different GNB species, the potent antibacterial activity, the pharmacokinetics properties, safety, and tolerability render cefiderocol a fundamental drug for the treatment of infections due MDR strains. Although this novel antimicrobial molecule has revolutionized the therapeutic antimicrobial armamentarium against MDR-GNB, the recent emergence of cefiderocol resistant strains have redefined its role in clinical practice and requested novel strategies to preserve its antibacterial activity. In this review, we discuss the mechanism of action of Cefiderocol, emerging resistance mechanisms, pharmacokinetic/pharmacodynamic (PK/PD) properties, efficacy data against the main Gram-negative bacteria, and future prospectives.

The present work demonstrates the optimization of the ligand structure in the series of bis-phosphine oxide and carbamoylphosphine oxide representatives for efficient coordination of Tb3+ and Eu3+ ions with the formation of the complexes exhibiting high Tb3+- and Eu3+-centered luminescence. The analysis of the stoichiometry and structure of the lanthanide complexes obtained by XRD method reveals the great impact of the bridging group nature between two phosphine oxide moieties on the coordination mode of the ligands with Tb3+ and Eu3+ ions. The bridging imido-group facilitates the deprotonation of imido-bisphosphine oxide ligand followed by the formation of tris-complexes. The spectral and PXRD analysis of the separated colloids indicates that the high stability of the tris-complexes provides their safe conversion into polystyrenesulfonate-stabilized colloids under the solvent exchange method. The red Eu3+-centered luminescence of the tris-complex exhibits the same specificity in the solutions and the colloids. The pronounced luminescent response on the antibiotics ceftriaxone allows to sense the latter in aqueous solutions with the LOD value equal to 0.974 M.