Nationwide increase of invasive ampicillin resistant Enterococcus faecium in the Netherlands

Abstract number: 1733_192

Top J., Willems R., van der Velden S., Asbroek M., Bonten M.

Objectives: We recently described an increase in the proportion of invasive enterococcal infections caused by ampicillin resistant Enterococcus faecium (AREfm) from 2% in 1994 to 32% in 2005 and a partially replacement of ampicillin-susceptible (ampS) E. faecalis by E. faecium (75% AREfm) among enterococcal bloodstream infections in our hospital (Top et al., CMI in press). In our hospital all AREfm belonged to CC17 E. faecium, a clonal complex associated with nosocomial outbreaks worldwide. A nationwide study was initiated to determine whether these ecological changes had also occurred in other hospitals in the Netherlands.

Methods: All 66 microbiology laboratories serving all hospitals of the country were asked to provide data on annual numbers of all invasive ampicillin resistant (ampR) enterococcal isolates and the first 30 enterococcal blood stream isolates (1 per patient) from 1994 until 2006. Multiplex PCR based on the ddl gene was performed to distinguish E. faecium and E. faecalis and susceptibility to ampicillin was determined.

Results: Thirty labs (45.5%) provided data, and 8 (12%) labs also provided isolates. The mean number of invasive ampR enterococcal isolates increased from 5 in 1994 to 25 in 2005. This increase was more pronounced in academic and large non-academic hospitals (>500 beds); from 5 in 1994 to 45 in 2005 in academic hospitals and from 4 in 1994 to 19 in 2005 in non-academic hospitals. Among enterococcal blood isolates proportions AREfm increased from 13% in 1993 to 40% in 2006; from 13% in 1993 to 51% in 2006 in academic hospitals and from 13% in 1999 to 26% in 2006 in non-academic hospitals. All E. faecalis isolates were ampicillin susceptible, while 75% of the E. faecium isolates were ampicillin resistant.

Conclusions: In the Netherlands invasive AREfm increased nationwide and have partially replaced ampS E. faecalis. The difference in prevalence among academic and non-academic hospitals probably reflects differences in patient population with haematology and transplant patients having the highest risks for AREfm bacteraemia being over represented in academic hospitals. All E. faecium isolates will be genotyped to determine the molecular epidemiology of AREfm in the Netherlands.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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