Molecular characterization of vancomycin-resistant enterococcus faecium isolates from mainland China

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Vancomycin-resistant enterococci (VRE) pose a significant global health threat.
• Limited data exists on VRE epidemiology and genetic characteristics in China.

Purpose of the Study:

• To characterize vancomycin-resistant Enterococcus faecium (VRE) isolates from China.
• To investigate the genetic elements responsible for vancomycin resistance and their dissemination.

Main Methods:

• Pulsed-field gel electrophoresis (PFGE) for VRE typing.
• Multilocus sequence typing (MLST) for strain characterization.
• Plasmid analysis and conjugation experiments to assess resistance transfer.

Main Results:

• Thirteen heterogeneous VanA-type VRE isolates were identified across five Chinese hospitals (2001-2005).
• Nine distinct sequence types (STs) were found, including five novel STs.
• Highly conjugative, novel plasmids (pZB18, pZB22) lacking the traA gene were identified.
• Thirteen Tn1546-like elements were classified into six types, with type II predominating.

Conclusions:

• The findings reveal novel genetic mechanisms of VRE in China, including unique conjugative plasmids.
• Plasmid-mediated transfer of Tn1546-like elements is a key driver for VRE dissemination among Enterococcus faecium strains.
• Further surveillance is crucial to monitor VRE spread in Chinese healthcare settings.