FAL/BMELV-Symposium "Futtermittelsicherheit"

A DNA microarray has been developed for the simultaneous characterization and typing of Salmonella enterica subsp. enterica isolates. One-hundred and nine 35-40mer oligonucleotides probes detect specific antibiotic resistance determinants, important virulence genes located within or outside the pathogenicity islands, flagellar and somatic antigens encoding genes, prophage genes and genes associated with metabolic pathways. The probes were printed on glass slides and whole genomic Cy5-labbeled Salmonella DNA was hybridized to the substrate. A set of 19 different Salmonella strains and one E. coli strain has been selected as positive and negative controls for each probe. The validity of the results are confirmed by gene specific PCRs or phenotypic methods (serotyping, MIC determination for various antimicrobial agents). Of 2071 data points generated, an agreement of 97.7% has been obtained between microarray and PCR/phenotypic results. One percent was classified as uncertain and 1.3 % showed a discordant result. The microarray described here is a new tool to study the epidemiology of Salmonella strains on the genotypic level and might become a powerful method for risk analysis. The BfR communicates the new tool to European scientists to stimulate further developments on that area. An extended microarray version (prototype 2) using 200 probes is in progress