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J. Bacteriol. doi:10.1128/JB.00664-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Five Genes Encoding Surface Exposed LPXTG Proteins are Enriched in Hospital-adapted Enterococcus faecium Clonal Complex-17 Isolates

Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands., Department of Medical Microbiology and Infectious Diseases, Erasmus MC-University Medical Center Rotterdam, Rotterdam, The Netherlands., Cell Microscopy Center, Department of Cell Biology, Institute of Biomembranes., Department of Internal Medicine, Division of Acute Internal Medicine and Infectious Diseases, Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands

^* To whom correspondence should be addressed. Email: a.hendrickx{at}umcutrecht.nl.

	Abstract

Most Enterococcus faecium isolates associated with hospital outbreaks and invasive infections belong to a distinct genetic subpopulation, called clonal complex-17 (CC17). It has been postulated that the genetic evolution of this CC17 involves the acquisition of various genes involved in antibiotic resistance, metabolic pathways and virulence. To gain insight in additional genes that may have favoured the rapid emergence of this nosocomial pathogen, we aimed to identify surface exposed LPXTG cell wall anchored proteins (CWAP), specifically enriched in CC17 E. faecium. Using PCR, Southern and dot-blot hybridizations, 131 E. faecium isolates (40 CC17 and 91 non-CC17) were screened for the presence of 22 putative CWAP genes identified from the E. faecium TX0016 genome. Five genes encoding LPXTG surface proteins were specifically enriched in E. faecium CC17 isolates. These five LPXTG surface protein genes were found in 28-40 (70-100%) of CC17 and in only 7-24 (8-26%) of non-CC17 isolates (p < 0.05). Three of these CWAP genes clustered together on the E. faecium TX0016 genome, which may comprise a novel Enterococcal pathogenicity island covering E. faecium contig 609. Expression at mRNA level was demonstrated and immuno transmission electron microscopy revealed association of the five LPXTG surface proteins with the cell wall. Minimal Spanning Tree analysis based on presence and absence of 22 CWAP genes revealed grouping of all 40 CC17 strains together with 18 hospital-derived but evolutionary unrelated non-CC17 isolates in a distinct CWAP enriched cluster, suggesting horizontal transfer of CWAP genes, and a role of these CWAPs in hospital adaptation.