A sustained endemic outbreak of vancomycin-resistant Enterococcus faecium: A 30-month surveillance study

Abstract

Background: The assessment of risk factors for the nosocomial acquisition of colonization and infection by vancomycin-resistant Enterococcus faecium (VRE_fm) is often problematic due to scarce data on antibiotic use. A 30-month prospective cohort study was conducted to characterize VRE_fm strains isolated during an outbreak and endemic period, identifying the risk factors, antibiotic consumption, and prevalence of virulence determinants. Methods: The study was conducted in a tertiary care hospital. A representative number (171 patients) of isolates that were classified as resistant to high-level vancomycin (minimum inhibitory concentration (MIC) ≥ 256 μg/ml) were investigated. Results: Among 171 colonized patients, 22 (12.9%) developed VRE infection. All VRE_fm isolates harboured vanA genes. Genes codifying virulence factors such as enterococcal surface protein (esp), aggregation substance 1 (asa1), and gelatinase (gelE) were detected in the VRE_fm studied. All patients infected with VRE had previously been colonized and became infected on average 14 days after colonization. Only previous use of aminoglycosides was a risk factor independently associated with VRE infection; however, glycopeptide consumption in defined daily doses (DDD) per 1000 patient-days was associated with the presence of this microorganism. The monthly colonization pressure ranged from 0.004% to 1.32% during the 30-month study period. Conclusions: We found a high incidence of VRE in a tertiary care hospital, independently associated with the prior use of aminoglycosides and the administration of glycopeptides.

Keywords::

• Outbreaks
• vancomycin-resistant enterococci
• colonization pressure

Acknowledgements

We thank V. P. Almeida for providing the strains of VRE_fm for this study and A. L. C. Darini for the control samples.

Declaration of interest: There is no conflict of interest. FAPEMIG financially supported this work.