Prevalence and Molecular Characterization of Vancomycin Variable Enterococcus faecium Isolated From Clinical...

Area of Science:

• Microbiology
• Molecular Biology
• Infectious Diseases

Background:

• Vancomycin-susceptible Enterococcus faecium (VSE) can harbor resistance genes.
• Vancomycin variable Enterococcus (VVE) are VSE isolates possessing the vanA gene.
• Understanding VVE prevalence and molecular characteristics is vital for infection control.

Purpose of the Study:

• To determine the prevalence of VVE among clinical VSE isolates.
• To elucidate the molecular structure of the vanA gene cluster in VVE.
• To assess the potential for VVE to acquire vancomycin resistance.

Main Methods:

• Collection of consecutive VSE isolates.
• Real-time PCR for vanA, vanB, and vanC gene detection.
• Overlapping PCR, whole-genome sequencing, and multilocus sequence typing for genetic analysis.
• Vancomycin exposure testing to assess resistance acquisition.

Main Results:

• 20 out of 282 VSE isolates (7.1%) were identified as VVE.
• Seventeen VVE isolates showed partial deletions in IS elements within vanS, vanR, or vanH.
• All VVE isolates belonged to the CC17 complex, with ST17, ST1421, and ST80 being dominant hospital-associated clones.
• 18 of 20 VVE isolates acquired vancomycin resistance after exposure.

Conclusions:

• VVE are present in clinical VSE isolates and can readily acquire vancomycin resistance.
• The molecular characterization reveals specific genetic alterations in VVE.
• Screening VSE for vanA is critical for identifying VVE and implementing appropriate treatment and infection control strategies.