Virulence of Enterococcus faecalis dairy strains in an insect model: the role of fsrB and gelE.
Despite the existence of various virulence factors in the Enterococcus genus, enterococcal virulence is still a debated issue. A main consideration is the detection of the same virulence genes in strains isolated from nosocomial or community-acquired infections, and from food products. The goal of this study was to evaluate the roles of two well-characterized enterococcal virulence factors, Fsr and gelatinase, in the potential virulence of Enterococcus faecalis food strains. Virulence of unrelated Enterococcus isolates, including dairy strains carrying fsr and gelE operons, was compared in the Galleria mellonella insect model. E. faecalis dairy strains were able to kill larvae and were as virulent as strain OG1RF, one of the most widely used for virulence studies. In contrast, Enterococcus durans and Enterococcus faecium strains were avirulent or poorly virulent for G. mellonella. To evaluate the role of fsrB and gelE in virulence of E. faecalis dairy strains, both genes were deleted independently in two strains. The Delta fsrB and Delta gelE deletion mutants both produced a gelatinase-negative phenotype. Although both mutations significantly attenuated virulence in G. mellonella, the Delta fsrB strains were more strongly attenuated. These results agree with previous findings suggesting the involvement of fsrB in the control of other cell functions relevant to virulence. Our work demonstrates that the presence of functional fsrB, and to a lesser extent gelE, in dairy enterococci should be considered with caution.
Gaspar
Frédéric
F
IBET and ITQB-UNL, Quinta do marquês, Av da República, 2781-901 Oeiras, Portugal.
Teixeira
Neuza
N
IBET and ITQB-UNL, Quinta do marquês, Av da República, 2781-901 Oeiras, Portugal.
Rigottier-Gois
Lionel
L
INRA-U888-UBLO, Domaine de Vilvert, 78352 Jouy en Josas cedex, France.
Marujo
Paulo
P
IBET and ITQB-UNL, Quinta do marquês, Av da República, 2781-901 Oeiras, Portugal.
Nielsen-LeRoux
Christina
C
INRA-U1249-GME, Domaine de la Minière, 78285 Guyancourt, France.
Crespo
Maria Teresa Barreto
MTB
IBET and ITQB-UNL, Quinta do marquês, Av da República, 2781-901 Oeiras, Portugal.
Lopes
Maria de Fátima Silva
MFS
IBET and ITQB-UNL, Quinta do marquês, Av da República, 2781-901 Oeiras, Portugal.
Serror
Pascale
P
INRA-U888-UBLO, Domaine de Vilvert, 78352 Jouy en Josas cedex, France.
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D013293:Enterococcus faecalis / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity*; D018093:Gelatinases / Q000235:genetics*; D017353:Gene Deletion; D009036:Moths / Q000382:microbiology; D009876:Operon; D017422:Sequence Analysis, DNA; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C409032:FsrB protein, Enterococcus; D037521:Virulence Factors; D018093:Gelatinases