Epidemic and Nonepidemic Multidrug-ResistantEnterococcus faecium

Helen L Leavis,Albert J De Neeling,Ellen M Mascini,Emile Spalburg,Andy Hoepelman,Rob J.L Willems,Ad C Fluit,Marc J.M Bonten,Janetta Top

doi:10.3201/eid0909.020383

Abstract

The epidemiology of vancomycin-resistant Enterococcus faecium (VREF) in Europe is characterized by a large community reservoir. In contrast, nosocomial outbreaks and infections (without a community reservoir) characterize VREF in the United States. Previous studies demonstrated host-specific genogroups and a distinct genetic lineage of VREF associated with hospital outbreaks, characterized by the variant esp-gene and a specific allele-type of the purK housekeeping gene (purK1). We investigated the genetic relatedness of vanA VREF (n=108) and vancomycin-susceptible E. faecium (VSEF) (n=92) from different epidemiologic sources by genotyping, susceptibility testing for ampicillin, sequencing of purK1, and testing for presence of esp. Clusters of VSEF fit well into previously described VREF genogroups, and strong associations were found between VSEF and VREF isolates with resistance to ampicillin, presence of esp, and purK1. Genotypes characterized by presence of esp, purK1, and ampicillin resistance were most frequent among outbreak-associated isolates and almost absent among community surveillance isolates. Vancomycin-resistance was not specifically linked to genogroups. VREF and VSEF from different epidemiologic sources are genetically related; evidence exists for nosocomial selection of a subtype of E. faecium, which has acquired vancomycin-resistance through horizontal transfer.

Highlights

Enterococcus faecium has become an important nosocomial pathogen, especially in immunocompromised patients, creating serious limitations in treatment options because of cumulative resistance to antimicrobial agents [1]
Other investigators described the variant esp gene in vancomycin-susceptible E. faecium (VSEF), and this gene appeared to be predominantly present among clinical isolates [15,16,17,18].These findings suggest the existence of a specific subpopulation of E. faecium, comprising both vancomycin-resistant Enterococcus faecium (VREF) as well as VSEF, associated with hospital outbreaks and infections
On the basis of our calculations of the identification factors of VSEF and representative isolates of different VREF genogroups, we found that isolates of cluster 1 (n=4) resembled those of genogroup A, previously allocated to nonhospitalized patients and pig-derived VREF (Table 2)

Summary

Introduction

Enterococcus faecium has become an important nosocomial pathogen, especially in immunocompromised patients, creating serious limitations in treatment options because of cumulative resistance to antimicrobial agents [1]. In the United States, prevalences of colonization and infection are high among hospitalized patients, but a community reservoir of VREF in healthy persons or animals seems to be absent [3,4]. Previous studies suggested host-specificity of VREF genogroups [11], and isolates associated with nosocomial outbreaks seemed to be genetically distinct from nonepidemic VREF isolated from humans and animals [12]. Other investigators described the variant esp gene in vancomycin-susceptible E. faecium (VSEF), and this gene appeared to be predominantly present among clinical isolates [15,16,17,18].These findings suggest the existence of a specific subpopulation of E. faecium, comprising both VREF as well as VSEF, associated with hospital outbreaks and infections. We further investigated the genetic relationship between VREF and VSEF isolates, derived from different epidemiologic sources, such as hospital out-

Methods

Results

Conclusion