Abstract: Objective: To monitor the Salmonella contamination status of commercial eggs, detect the pathogenesis and pathogenicity island (SPI) gene of Salmonella isolates and their correlation. Methods: Commercial eggs were collected from supermarkets in different cities in Shaanxi province. The eggshell membranes were harvested for isolating and culturing Salmonella in eggs. The strain isolates were identified through the PCR amplification of the special gene invA from Salmonella. The isolated strains were used for testing the pathogenesis for chicken. According to the sequence of SPI genes published in GenBank, PCR primers were designed to amplify and identify the SPI genes of core proteins. Results: A total of 30 Salmonella strains were isolated from 1100 commercial eggs that were purchased from 55 supermarkets. According to animal pathogenesis tests, 13 strains were pathogenic and 7 strains were strongly pathogenic among these Salmonella strains. The carrying rate of SPI gene was 60% for SPI-1, 73.3% for SPI-2, 100% for SPI-3, 90% for SPI-4 and 76.7% for SPI-5. Meanwhile, SPI-1 and SPI-2 revealed an obvious correlation with pathogenesis. Conclusion: The isolation rate of Salmonella from commercial eggs observed in this study is 2.73%. SPI-1 and SPI-2 have a positive correlation with pathogenesis.

Key words: Salmonella, invA gene, pathogenesis, SPI, egg, eggshell membrane