Comparative genomics of Enterococcus faecalis from healthy Norwegian infants.
BACKGROUND
Enterococcus faecalis, traditionally considered a harmless commensal of the intestinal tract, is now ranked among the leading causes of nosocomial infections. In an attempt to gain insight into the genetic make-up of commensal E. faecalis, we have studied genomic variation in a collection of community-derived E. faecalis isolated from the feces of Norwegian infants.


RESULTS
The E. faecalis isolates were first sequence typed by multilocus sequence typing (MLST) and characterized with respect to antibiotic resistance and properties associated with virulence. A subset of the isolates was compared to the vancomycin resistant strain E. faecalis V583 (V583) by whole genome microarray comparison (comparative genomic hybridization (CGH)). Several of the putative enterococcal virulence factors were found to be highly prevalent among the commensal baby isolates. The genomic variation as observed by CGH was less between isolates displaying the same MLST sequence type than between isolates belonging to different evolutionary lineages.


CONCLUSIONS
The variations in gene content observed among the investigated commensal E. faecalis is comparable to the genetic variation previously reported among strains of various origins thought to be representative of the major E. faecalis lineages. Previous MLST analysis of E. faecalis have identified so-called high-risk enterococcal clonal complexes (HiRECC), defined as genetically distinct subpopulations, epidemiologically associated with enterococcal infections. The observed correlation between CGH and MLST presented here, may offer a method for the identification of lineage-specific genes, and may therefore add clues on how to distinguish pathogenic from commensal E. faecalis. In this work, information on the core genome of E. faecalis is also substantially extended.
Solheim
Margrete
M
Laboratory of Microbial Gene Technology and Food Microbiology, Department of Chemistry, Biotechnology and Food Science, The Norwegian University of Life Sciences, As, Norway. margrete.solheim@umb.no
Aakra
Agot
A
Snipen
Lars G
LG
Brede
Dag A
DA
Nes
Ingolf F
IF
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015373:Bacterial Typing Techniques / Q000379:methods*; D001430:Bacteriocins / Q000096:biosynthesis; D055028:Comparative Genomic Hybridization / Q000379:methods*; D013293:Enterococcus faecalis / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D005243:Feces / Q000382:microbiology; D005260:Female; D018093:Gelatinases / Q000235:genetics / Q000378:metabolism; D023281:Genomics / Q000379:methods*; D006801:Humans; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D009664:Norway; D054353:Perforin / Q000096:biosynthesis; D010802:Phylogeny; D037521:Virulence Factors / Q000235:genetics
D001426:Bacterial Proteins; D001430:Bacteriocins; D037521:Virulence Factors; D054353:Perforin; D018093:Gelatinases