Genotypic and phenotypic characterization of vancomycin-resistant enterococcus faecium from clinical and surveillance samples in northern Thailand.

OBJECTIVES

Vancomycin-resistant Enterococcus faecium (VREfm) is a significant cause of hospital-acquired infections due to its multidrug resistance, environmental persistence, and high transmissibility. This study aimed to characterize clinical and surveillance VREfm isolates by examining antimicrobial resistance profiles, virulence gene distribution, biofilm formation, and genetic background.

METHODS

A total of 107 VREfm isolates (43 clinical, 64 surveillance) were collected from Maharaj Nakorn Chiang Mai Hospital. Antimicrobial susceptibility testing, PCR detection of resistance and virulence genes, and biofilm formation using the crystal violet assay were performed. Whole genome sequencing (WGS) was conducted on four representative isolates.

RESULTS

Most clinical isolates (88.4%) were from urine samples, while all surveillance isolates were obtained from rectal swabs. The majority of patients (74-75%) were over 60 years old. All isolates exhibited resistance to ampicillin, penicillin, ciprofloxacin, levofloxacin, and vancomycin, with some showing high-level gentamicin resistance. The vanA gene was detected in all isolates, corresponding with vancomycin MICs ≥64 µg/mL. Virulence genes esp, hyl, acm, and sagA were detected in 96.9-100% of isolates. Moderate biofilm formation was observed in 83.7% of clinical and 68.7% of surveillance isolates, particularly among those carrying multiple virulence genes. WGS identified two sequence types; ST17 and ST262, which shared similar resistance and virulence profiles.

CONCLUSIONS

Clinical and surveillance VREfm isolates exhibited comparable resistance and virulence characteristics. These findings underscore the need for continuous surveillance of VREfm in hospitals, particularly among high-risk populations, to prevent infections and improve treatment strategies.