The Y58D mutation in rpsJ gene is correlated with tigecycline and eravacycline combined resistance in ST80 vancomycin-resistant Enterococcus faecium isolates

Objectives: To describe the phenotypic and genetic features of vancomycin-resistant Enterococcus faecium (VREfm) isolates exhibiting resistance to tetracycline (TET), tigecycline (TGC) and eravacycline (ERV). Methods: Between December 2023 and September 2024, 32 vancomycin-resistant Enterococci (VRE) were collected from clinical samples at the Policlinico Foggia, Italy. Bacterial identification was carried out by mass spectrometry analysis (MALDI-TOF). Antimicrobial susceptibility testing for vancomycin (VA), TET, TGC and ERV was performed by reference broth microdilution method. Whole-genome sequencing (WGS) was carried out to explore the content of tetracyclines resistance determinants, and the phylogenetic relationship between isolates (in silico MLST and SNPs analysis). Results: Among studied isolates, thirty and two were E. faecium and Enterococcus faecalis (Efs), respectively. Overall, eight isolates, six VREfm and two VREfs, were resistant to TET (8/32, 25%), with four (all VREfm) being resistant to TGC and ERV (4/32, 12.5%), also. The two TET-resistant VREfs strains belonged to ST6 and carried the tet(M) gene only. All the TET-resistant VREfm were ST80 and carried tet(L) and tet(M) genes. Among these, the four TGC-resistant and ERV-resistant strains showed an uncommon Y58D substitution in the ribosomal S10 protein (rpsJ gene). SNPs analysis revealed that Y58D-carrying strains formed a separate cluster, within ST80 VREfm. Conclusions: In this study we correlated the presence of the Y58D mutation in the rpsJ gene with resistance to TGC and ERV in a cluster of VREfm ST80 clinical strains. The Y58D mutation was invariably found in co-presence with tet(L) and tet(M) genes.