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Vancomycin resistance emerging in a clonal outbreak caused by ampicillin-resistant Enterococcus faecium
S Harthug1, A Digranes, O Hope
1Department of Medicine, The Gade Institute, Haukeland University Hospital, Bergen, Norway. stig.harthug@haukeland.no
Summary
Norway experienced its first hospital-acquired outbreak of ampicillin-resistant Enterococcus faecium (ARE) in 1995, which is still ongoing. Vancomycin-resistant Enterococcus faecium (VRE) emerged a year later, particularly in areas with high vancomycin use.
Area of Science:
- Infectious Diseases
- Microbiology
- Hospital Epidemiology
Background:
- Nosocomial outbreaks pose significant public health challenges.
- Emergence of antibiotic resistance, such as ampicillin-resistant Enterococcus faecium (ARE), necessitates surveillance.
- Understanding the dynamics of ARE and vancomycin-resistant Enterococcus faecium (VRE) is crucial for infection control.
Purpose of the Study:
- To document the initial nosocomial outbreak of ARE in Norway.
- To investigate the emergence and characteristics of vancomycin-resistant Enterococcus faecium (VRE) in relation to the ARE outbreak.
- To analyze clinical data and genomic relatedness of ARE and VRE isolates.
Main Methods:
- Systematic registration of all ARE and VRE cases in a region of 1 million people.
- Genomic characterization of isolates using pulsed-field gel electrophoresis (PFGE).
- Retrospective collection and analysis of clinical data from affected patients.
Main Results:
- 149 patients infected with ARE, with 115 linked to the outbreak strain; common infections included urinary tract infections (97) and bacteremia (14).
- 16.1% of ARE patients died during hospitalization; 93% had prior antibiotic exposure.
- Four vanB-type VRE infections were identified, genomically related to the ARE strain, with VRE emergence correlating with increased vancomycin use.
Conclusions:
- Norway's first nosocomial ARE outbreak began in 1995 and remains active.
- VRE appeared in wards with higher vancomycin consumption approximately one year after the ARE outbreak's onset.
- These findings highlight the importance of antimicrobial stewardship in preventing the spread of resistant organisms.