Molecular characterization of vancomycin-resistant Enterococcus faecium isolated from intensive care units

Area of Science:

• Microbiology
• Infectious Diseases
• Molecular Epidemiology

Background:

• Vancomycin-resistant enterococci (VRE) are a growing concern in healthcare settings.
• Understanding the molecular epidemiology of VRE is crucial for infection control.

Purpose of the Study:

• To molecularly characterize vancomycin-resistant enterococci (VRE) isolates from intensive care units (ICUs).
• To investigate the genetic basis and dissemination patterns of VRE in Iranian hospitals.

Main Methods:

• Prospective observational study collecting 546 enterococci isolates.
• Pulsed-field gel electrophoresis (PFGE) for typing VRE isolates.
• Long PCR restriction fragment length polymorphism (L-PCR RFLP) and sequencing to analyze the Tn1546 transposon and vanA gene location via DNA hybridization.

Main Results:

• 33 isolates (6%) were identified as VRE, with 11 (34%) from ICUs.
• VRE were predominantly isolated from urinary tract infections (18 isolates, 55%).
• PFGE identified five common types (CT) and 13 single types (ST), with two major CTs and one ST among ICU isolates.
• Two distinct lineages of the Tn1546 transposon were identified.
• The vanA gene was consistently located on the genome in most VRE isolates.

Conclusions:

• A limited number of VRE clonal types are disseminated within Iranian ICUs.
• These VRE strains possess the vanA gene and exhibit high conjugation frequency, facilitating spread.
• Molecular surveillance is essential for controlling VRE transmission in healthcare environments.