Key factors in screening for resistant enterococci: a narrative synthesis of current evidence

Abstract

Background and aim Enterococci, naturally found in the gut, can be largely resistant to antibiotics. While the enterococci rarely cause disease, the bacteria pose a higher risk to immunocompromised patients. Vancomycin resistant enterococci (VRE), linezolid resistant enterococci (LRE) and linezolid-and vancomycin resistant enterococci (LVRE) are particularly challenging and a focus for infection prevention. VRE, especially Enterococcus faecium (VREfm), is rising in Europe and listed by WHO as a priority pathogen due to its resistant capabilities. Currently, it is not possible to clear enterococcal carriage. VRE is notifiable in Norway, and it is voluntary to send isolates to the reference laboratory for surveillance in Denmark. National prevention guidelines were updated in 2015 and 2016, in Norway and Denmark respectively. In 2023, the Norwegian Institute of Public Health (NIPH) and the Statens Serum Institut (SSI) decided to collaborate on proposals for new national recommendations for screening, targeting resistant microbes of special significance to healthcare. We conducted literature reviews to update screening recommendations for resistant microbes in healthcare. This literature review is part of a series of reviews aimed at providing evidence to support this process. Methods We systematically searched five databases for systematic reviews and primary literature from the Nordic countries and the Netherlands. Inclusion criteria included whether outcomes were duration of colonisation, risk of transmission, prevalence of resistant enterococci among different patient populations and in different settings, or individual factors associated with resistant enterococci colonisation or infection. We excluded studies on treatment, management, laboratory methods, drug resistance, and environmental screening. We chose not to include a discussion section in this report, as the interpretation of the results will be addressed in a more comprehensive assessment, which will incorporate all evidence syntheses along with other considerations. Results In our search, we found 14 studies to be relevant. All studies involved VRE, and no studies on LRE were identified. Assessments of duration of colonisation and long-time carriage remain challenging based on identified studies, but there might be a trend that that persistent colonization decreases over time. Studies on risk of infection/colonisation with VRE after exposure to an infected/colonised roommate and rooms previously occupied by infected/colonised patients are inconclusive. The exposure may increase the risk of transmission, but the evidence is scarce. Studies on the prevalence of VRE in different patient populations mainly focuses on pooled prevalences of patients from different settings in the world, and interpretation of the results should be done with caution. This narrative synthesis found clear evidence that previous antibiotic use, especially vancomycin, was a risk factor for VRE colonisation or infection. Other associated factors were recent hospitalisation, ICU stay, invasive devices, wounds, and incontinence. Conclusion This review showed that persistent VRE colonisation may decrease over time. Evidence on transmission risks remains inconclusive. Key risk factors include prior antibiotic use, especially vancomycin, as well as hospitalisation, ICU stay, invasive devices, wounds, and incontinence.