Stability of vancomycin-resistant enterococcal genotypes isolated from long-term-colonized patients

Area of Science:

• Microbiology
• Infectious Diseases
• Molecular Epidemiology

Background:

• Vancomycin-resistant enterococci (VRE) are a significant cause of healthcare-associated infections.
• Understanding the genetic diversity and stability of VRE strains is crucial for effective infection control and epidemiological studies.
• Pulsed-field gel electrophoresis (PFGE) is a common method for bacterial strain typing.

Purpose of the Study:

• To investigate the genotypic variation and stability of vancomycin-resistant enterococci (VRE) isolates.
• To determine the genetic diversity among VRE strains in an endemic setting.
• To assess the applicability of pulsed-field gel electrophoresis (PFGE) for VRE strain definition.

Main Methods:

• Analysis of 455 VRE isolates using pulsed-field gel electrophoresis (PFGE).
• Identification of distinct PFGE types.
• Comparison of vanA and vanB Enterococcus faecium strain types.
• Evaluation of VRE isolate variation within individual patients over time.

Main Results:

• Twenty-two distinct PFGE types were identified among the 455 VRE isolates.
• Comparisons of vanA Enterococcus faecium strain types consistently showed greater than 10 band differences.
• Over 85% of vanA and vanB E. faecium isolates from individual patients exhibited fewer than 3 band differences, indicating low genetic variation.
• Analysis of all strains revealed two distinct peaks of band differences: < 3 and > 10, suggesting distinct VRE populations.

Conclusions:

• VRE isolates demonstrate significant genetic dichotomy, being either closely related or highly divergent.
• VRE strains within individual patients exhibit minimal genetic variation over time.
• PFGE is a suitable method for studying the epidemiology of endemic VRE.