Microarray analysis of virulence gene profiles in Salmonella serovars from food/food animal environment

Rapid, accurate and inexpensive analysis of the disease-causing potential of foodborne pathogens is an important consideration in food safety and biodefense, particularly in developing countries. The objective of this study is to demonstrate the use of a robust and inexpensive microarray platform to assay the virulence gene profiles in Salmonella from food and/or the food animal environment, and then use ArrayTrack™ for data analysis.

The spotted array consisted of 69 selected Salmonella-specific virulence gene probes (65bp each). These probes were printed on poly-L-lysine-coated slides. Genomic DNA was digested with Sau3AI, labeled with Cy3 dye, hybridized to the gene probes, and the images were captured and analyzed by GenePix 4000B and ArrayTrack™, a free software developed by Food and Drug Administration (FDA) researchers.

Nearly 58% of the virulence-associated genes tested were present in all Salmonella strains tested. In general, genes belonging to inv, pip, prg, sic, sip, spa or ttr families were detected in more than 90% of the isolates, while the iacP, avrA, invH, rhuM, sirA, sopB, sopE or sugR genes were detected in 40 to 80% of the isolates. The gene variability was independent of the Salmonella serotype.

This hybridization array presents an accurate and cost-effective method for evaluating the disease-causing potential of Salmonella in outbreak investigations by targeting a selective set of Salmonella-associated virulence genes.