Review of Enterococcus faecalis Infections of Poultry

Enterococcus faecalis organisms are Gram-positive cocci that are ubiquitous in the environment, occurring in water and soil, and are commensal inhabitants of the intestinal tracts of both vertebrate and invertebrate animals. They are considered opportunists and possess many virulence-encoding traits, including the formation of biofilms and toxins. Enterococcus faecalis produces cytolysin, which is a unique toxin having activity against both eukaryotic and prokaryotic cells. Cytolysin causes hemolysis of red blood cells and has also been termed hemolysin. Enterococcus faecalis organisms are intrinsically resistant to some antibiotics and can transmit antimicrobial resistance to other microorganisms. In poultry, there is ample evidence to indicate that E. faecalis can be egg transmitted, causing decreased hatchability of eggs. Enterococcus faecalis has been found to rapidly spread among hatchlings that are exposed in the hatcher. In older birds, some E. faecalis isolates cause amyloid arthropathy. Various methods have been developed to assess E. faecalis isolates for virulence-encoding traits, including Multilocus sequence typing and embryo lethality assays. However, much variability occurs in interpreting the results of these methods and the correlation between genotypes, phenotypes, and virulence has not been well established. The virulence traits and pathogenesis of E. faecalis in poultry need to be elucidated further.