First Isolation of Vancomycin-Resistant Enterococcus faecium Carrying Plasmid-Borne vanD1

Area of Science:

• Microbiology
• Molecular Biology
• Infectious Diseases

Background:

• Enterococcus faecium is a significant cause of hospital-acquired infections.
• Vancomycin resistance in E. faecium is a growing public health concern.
• The vanD gene cluster confers resistance to vancomycin.

Purpose of the Study:

• To characterize a vancomycin-resistant Enterococcus faecium strain isolated from a Japanese patient.
• To investigate the genetic basis of vancomycin resistance in the isolated strain.
• To assess the transferability of the resistance gene.

Main Methods:

• Isolation and identification of Enterococcus faecium from a fecal sample.
• Antimicrobial susceptibility testing (MIC determination for vancomycin and teicoplanin).
• Plasmid DNA analysis and gene sequencing (vanD1 gene detection).
• Conjugation experiments to assess gene transfer.

Main Results:

• Isolation of vancomycin-resistant Enterococcus faecium strain JH5687 carrying the vanD1 gene on plasmid pEF-D.
• Strain JH5687 exhibited moderate vancomycin resistance (MIC = 16 μg/mL) but remained susceptible to teicoplanin (MIC = 1 μg/mL).
• Plasmid pEF-D showed high homology to known conjugative plasmids, and strain JH5687 demonstrated a conjugation frequency of 10^-4 to 10^-5 per donor cell.

Conclusions:

• The vanD1 gene on plasmid pEF-D is responsible for vancomycin resistance in E. faecium strain JH5687.
• The genetic organization of pEF-D is similar to other conjugative plasmids, suggesting efficient horizontal gene transfer.
• The susceptibility to teicoplanin offers a potential therapeutic alternative for infections caused by this strain.