Virulent synergistic effect between Enterococcus faecalis and Escherichia coli assayed by using the Caenorhabditis elegans model.
BACKGROUND
The role of enterococci in the pathogenesis of polymicrobial infections is still debated. The purpose of this study was to evaluate the effect of virulent enterococci in the presence or absence of Escherichia coli strains in the in vivo Caenorhabditis elegans model.


RESULTS
This study demonstrated that there was a synergistic effect on virulence when an association of enterococci and E. coli (LT50 = 1.6 days+/-0.1 according to the tested strains and death of nematodes in 4 days+/-0.5) was tested in comparison with enterococci alone (LT50 = 4.6 days+/-0.1 and death in 10.4 days+/-0.6) or E. coli alone (LT50 = 2.1+/-0.9 and deaths 6.6+/-0.6) (p<0.001). In addition, there was a relation between the virulence of E. faecalis strains alone and the virulence potential of the association with E. coli strains. Finally, in the presence of avirulent E. coli strains, enterococci have no effect (LT50 = 4.3+/-0.5 and deaths in 10.8+/-0.8), independently of the level of their own virulence, demonstrating that the 'enterococci effect' only occurred in the presence of virulent E. coli strains.


CONCLUSIONS
This study allows a better understanding of a bacterial cooperation. Moreover, it could help to optimize the antibiotic regimen during polymicrobial infections.
Institut National de la Santé et de la Recherche Médicale, ESPRI 26, Université Montpellier 1, UFR de Médecine, Nîmes, France.
Jean-Philippe
JP
Lavigne
Marie-Hélène
MH
Nicolas-Chanoine
Gisèle
G
Bourg
Jérôme
J
Moreau
Albert
A
Sotto
D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001424:Bacterial Infections / Q000188:drug therapy / Q000503:physiopathology*; D017173:Caenorhabditis elegans / Q000382:microbiology* / Q000502:physiology; D004195:Disease Models, Animal; D013293:Enterococcus faecalis / Q000472:pathogenicity*; D004926:Escherichia coli / Q000472:pathogenicity*; D005838:Genotype; D012044:Regression Analysis; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
D000900:Anti-Bacterial Agents; D037521:Virulence Factors