Barceló, Isabel MaríaEscobar-Salom, MariaJordana-Lluch, ElenaTorrens, GabrielOliver, AntonioJuan, Carlos2024-10-092024-10-092024-01-02Barceló IM, Escobar-Salom M, Jordana-Lluch E, Torrens G, Oliver A, Juan C. Filling knowledge gaps related to AmpC-dependent β-lactam resistance in Enterobacter cloacae. Sci Rep. 2024 Jan 2;14(1):189.https://hdl.handle.net/20.500.13003/20131https://hdl.handle.net/20.500.12105/23830Enterobacter cloacae starred different pioneer studies that enabled the development of a widely accepted model for the peptidoglycan metabolism-linked regulation of intrinsic class C cephalosporinases, highly conserved in different Gram-negatives. However, some mechanistic and fitness/virulence-related aspects of E. cloacae choromosomal AmpC-dependent resistance are not completely understood. The present study including knockout mutants, β-lactamase cloning, gene expression analysis, characterization of resistance phenotypes, and the Galleria mellonella infection model fills these gaps demonstrating that: (i) AmpC enzyme does not show any collateral activity impacting fitness/virulence; (ii) AmpC hyperproduction mediated by ampD inactivation does not entail any biological cost; (iii) alteration of peptidoglycan recycling alone or combined with AmpC hyperproduction causes no attenuation of E. cloacae virulence in contrast to other species; (iv) derepression of E. cloacae AmpC does not follow a stepwise dynamics linked to the sequential inactivation of AmpD amidase homologues as happens in Pseudomonas aeruginosa; (v) the enigmatic additional putative AmpC-type β-lactamase generally present in E. cloacae does not contribute to the classical cephalosporinase hyperproduction-based resistance, having a negligible impact on phenotypes even when hyperproduced from multicopy vector. This study reveals interesting particularities in the chromosomal AmpC-related behavior of E. cloacae that complete the knowledge on this top resistance mechanism.enghttp://creativecommons.org/licenses/by/4.0/Bacterial Proteinsbeta-Lactam ResistancePeptidoglycanMicrobial Sensitivity TestsCephalosporinasebeta-LactamasesEnterobacter cloacaeresearch articleAtribución 4.0 Internacional3816798614118910.1038/s41598-023-50685-110.1038/s41598-023-50685-12045-2322Scientific reportsopen accessEnterobacter cloacaePruebas de Sensibilidad MicrobianaCefalosporinasaPeptidoglicanoProteínas Bacterianasbeta-LactamasasResistencia betalactómica