In research sponsored by the USPOULTRY Foundation, Dr. Donald Reynolds of the School of Veterinary Medicine and Biomedical Sciences, University of Nebraska developed an embryo lethality assay to distinguish between highly virulent and pathogenic strains of Enterococcus faecalis.  Concurrently, his laboratory applied matrix assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) to distinguish among isolates. 

Research was conducted on 52 isolates of E. faecalis obtained from broilers, laying hens, turkeys and game birds.  The embryo lethality assay provided a semi-quantifiable index of pathogenicity.  This is necessary since additional molecular assays on either high or low pathogenicity strains would indicate the exotoxins produced that are responsible for embryo mortality and specific pathology.  The MALDI-TOF MS assays could distinguish between virulent and innocuous strains but lacked the ability to distinguish among strains of intermediate pathogenicity suggesting additional research to refine the technique.