Enterococcus faecium
Enterococcus faecium is a Gram-positive coccus increasingly implicated in healthcare-associated infections, particularly among immunocompromised or long-term hospitalized patients. Its rising resistance to vancomycin has positioned vancomycin-resistant E. faecium (VREfm) as a pathogen of major clinical and public health concern.
In Taiwan, through the national TSAR (Taiwan Surveillance of Antimicrobial Resistance) program, we analyzed over 1,100 clinical isolates between 2004 and 2018, with 229 VREfm isolates subjected to whole genome sequencing (WGS). ST17 and ST78 were identified as predominant clones, with ST17 rising dramatically from 14.6% to 47.5%. The vanA gene was typically carried on Tn1546-like transposons, and a type II variant with IS1678 has become dominant since 2008, indicating enhanced transmissibility and genetic mobility.
Of growing concern, these multidrug-resistant strains—resistant to ampicillin, tetracyclines, macrolides, and fluoroquinolones—are increasingly causing bloodstream infections. A nationwide 18-year study published from our TSAR surveillance revealed that E. faecium bacteremia cases increased from 0.8% to 1.8% between 2002 and 2020 (P < 0.001), and by 2020, nearly half (47.4%) of E. faecium bloodstream isolates were vancomycin-resistant. This contrasts with declining trends observed in the U.S. and China, highlighting the unique and escalating challenge in Taiwan.
These findings, published in Journal of Global Antimicrobial Resistance and Microbiology Spectrum, emphasize the need for continued genomic surveillance and the implementation of robust antimicrobial stewardship strategies to mitigate the burden of VREfm in Taiwan.
References
1. Huang YC, Chen FJ, Huang IW, et al. Clonal expansion of Tn1546-like transposon-carrying vancomycin-resistant Enterococcus faecium, a nationwide study in Taiwan, 2004–2018. J Glob Antimicrob Resist. 2024 Jul 10:S2213-7165(24)00117-6. https://doi.org/10.1016/j.jgar.2024.07.003
2. Huang YC, Kuo SC, Fang CT, Lauderdale TL. Changing epidemiology and antimicrobial resistance of bacteria causing bacteremia in Taiwan: 2002–2020. Microbiol Spectr. 2024;12(8):e00608-24. https://doi.org/10.1128/spectrum.00608-24
Enterococcus faecalis
Enterococcus faecalis is a commensal bacterium of the human gastrointestinal tract, but it is also an opportunistic pathogen causing a range of infections, including urinary tract infections, endocarditis, and intra-abdominal infections. In recent years, the emergence of linezolid-resistant E. faecalis carrying the optrA gene has raised public health concerns, particularly with evidence suggesting potential zoonotic transmission.
Our recent investigations incorporate both human clinical isolates and retail meat samples, revealing that optrA-positive E. faecalis are present in both sources. Preliminary genomic analysis indicates the presence of mobile genetic elements-mediated resistance and potential cross-host dissemination pathways. These findings underscore the importance of a One Health approach in antimicrobial resistance surveillance, recognizing the interconnectedness of human, animal, and environmental health.
Ongoing work focuses on WGS-based phylogenomic comparison to assess the genetic relatedness and evolutionary trajectories of human- and animal-derived isolates. The ultimate goal is to inform risk assessment and develop evidence-based recommendations for AMR mitigation strategies in both clinical and agricultural settings.