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.