Tn916-like element EfaB5 genes are highly conserved in invasive Enterococcus faecalis and CC17 Enterococcus faecium

Abstract number: P2040

Leavis H.L., Bonten M.J.M., Schuren F.H., Asbroek M., Caspers M.P.M., Willems R.J.L.

Objectives:Enterococcus faecalis and Enterococcus faecium have evolved in high-risk enterococcal clonal complexes (HiRECC). HiRECC from both species are emerging as nosomial pathogens, most notably the E. faecium Clonal Complex 17 (CC17). The extent of virulence gene exchange between both species, however, is unknown.

Methods: We assessed the presence of orthologs in 16 blood culture E. faecalis and 97 E. faecium of which 40 belonged to the HiRECC CC17, through hybridisation to an E. faecium mixed whole genome microarray (Leavis et al. PLoS Pathog 2007). In addition, we performed an in silico hybridisation of E. faecalis V583 and the unfinished E. faecium DO genome, and interspecies 16s rRNA and MLST genes comparisons. PCR and direct sequencing were used to analyse the spatial arrangement of EfaB5 variant genes in E. faecium DO.

Results:E. faecalis and E. faecium shared only 233 spots (4.4%) in microarray hybridisation of which 58 were >80% specific for CC17 E. faecium (sensitivity: 26–98%). Sequencing revealed that eight spots represented genes, present in seven E. faecalis strains (n[HiRECC]=5), highly similar to genes previously found on EfaB5, an E. faecalis Tn916-like element containing several genes related to virulence in other species. An in silico genome comparison, identified 24 E. faecium DO genes, with >85% sequence identity with EfaB5, thus confirming the presence of an element similar to EfaB5 in E. faecium. Analysis of spatial arrangements of the EfaB5 orthologues in E. faecium DO revealed a conserved 3' end of this mobile element, while genes with high identity (>95%) to the 5'-end of EfaB5 were found to be scattered on the E. faecium DO chromosome. In contrast to the high similarity of EfaB5 genes, the sequence identity of the core genomes of the two species is low, which is reflected by the relative high average of 16S rRNA sequence divergence (4.1%) and the low average nucleotide identity of housekeeping genes (74.2%).

Conclusion: The presence of highly similar genes in CC17 and HiRECC E. faecalis suggests genetic exchange between the most prevalent clinical enterococcal subpopulations, in which EfaB5 might have played a role in niche adaptation. Scattered presence of part of the EfaB5 variant genes in E. faecium DO, suggests either recombination after integration or acquisition at different occasions.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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