Genetic analysis of vancomycin-variable Enterococcus faecium clinical isolates in Italy

• DOI: 10.1007/s10096-024-04768-0
• Publication Date: 2024-01-31T21:22:33Z
• Authors: Sonia Nina Coccitto; Marzia Cinthi; Serena Simoni; Antonella Pocognoli; Guido Zeni; Annarita Mazzariol; Gianluca Morroni; Marina Mingoia; Eleonora Giovanetti; Andrea Brenciani; Carla Vignaroli
• Keywords: Enterococcus faecium; Multilocus sequence typing; Enterococcus faecalis

Abstract Purpose To investigate the occurrence of vancomycin-variable enterococci (VVE) in a hospital central Italy. Methods vanA positive but vancomycin-susceptible Enterococcus faecium isolates (VVE-S) were characterized by antibiotic susceptibility tests, molecular typing (PFGE and MLST), WGS approach. The reversion VVE-S to resistant phenotype was assessed exposure increasing vancomycin concentrations, revertant used filter mating experiments. qPCR analyze plasmid copy number. Results Eleven putative selected. revealed two categories cluster located: first type showed lack vanR , deletion vanS an intact vanH / vanX cluster; second devoid both 544-bp at 5′-end . Strains ( n = 7) carrying considered able regain resistance (VVE-R) presence vancomycin, due 44-bp promoter region vanH/vanA/vanX causing its constitutive expression. VVE-R strains not transfer conjugation, unstable: after 11 days growth without selective pressure, revertants still lower MIC. A higher number probably related phenotype. Conclusion We highlight importance VVE transition VRE under therapy resulting potential failure treatment. also report first-time identification pstS -null belonging ST1478.