An Alternative Method to Evaluate the Virulence of Salmonella Enteritidis Challenge Strain using Embryonated Chicken Eggs

The chicken pathogenicity test is an old method to determine the bacterial virulence. In the present study, ELA (Embryo Lethality Assay) was designed as an alternative, rapid and easy model to evaluate the S. Enteritidis virulence. Previously confirmed virulent and avirulent strains, using the traditional chicken pathogenicity method, were used to apply the ELA. Based on ELD50 (50% embryo lethal dose) calculation, virulent strain has 3.6 Log10 ELD50 but the avirulent strain has 6 Log10 ELD50. Strain virulence was determined according to bacterial count in the allantoic cavity (AC) fluid and rate of liver invasion score. The virulent strain count in the allantoic fluid was declined and maintained to 107 CFU/ml on the 5th post inoculation, but the avirulent strain declined to 106 CFU/ml. The bacterial load of embryonic liver of virulent strain was about 10,000 times more than the avirulent one on the 5th post inoculation. In conclusion, these results recommend the application of embryonated chicken eggs assay as an alternative method to evaluate the virulence of Salmonella Enteritidis challenge strain