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 Enterococci (VRE) isolates exhibiting resistance to tetracycline (TET), tigecycline (TGC), and eravacycline (ERV).

METHODS: Between December 2023 and September 2024, 32 VRE were collected from clinical samples at the Policlinico Foggia, Italy. Bacterial identification was carried out by matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis. Antimicrobial susceptibility testing for vancomycin, TET, TGC, and ERV was performed by the reference broth microdilution method. Whole-genome sequencing was carried out to explore the content of tetracycline resistance determinants, and the phylogenetic relationship between isolates (in silico multilocus sequence typing [MLST] and single-nucleotide polymorphisms [SNPs] analysis).

RESULTS: Among the studied isolates, 30 and 2 were vancomycin-resistant Enterococcus faecium (VREfm) and vancomycin-resistant Enterococcus faecalis (VREfs), 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 sequence type (ST)6 and carried the tet(M) gene only. All the TET-resistant VREfm were ST80 and carried the 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 the tet(L) and tet(M) genes.