Y-017. Predicting Salmonella enterica subsp. enterica Serotypes by Repetitive Extragenic Palindromic Sequence-Based PCR

B. S. Seal1, M. G. Wise2, G. R. Siragusa1, J. Plumblee1, P. F. Cray1, E. H. Atkins2, T. A. Ross2, M. Healy2;
1USDA/ARS, Athens, GA, 2Bacterial Barcodes, Athens, GA.

Background: Repetitive extragenic palindromic sequence-based PCR (rep-PCR) which can be used to genotype microorganisms was evaluated as a method to predict the serotype of Salmonella isolates. Methods: Two hundred and thirty-three Salmonella isolates belonging to 14 frequently isolated serotypes from poultry were used to create a DNA fingerprint library with the DiversiLab software. Subsequently, a blinded set of 42 poultry-related Salmonella isolates were typed with the DiversiLab System, and queried against the library in an attempt to putatively assign a serotype designation. The query isolates were previously serotyped employing standard techniques. Results: Using clustering of the resultant microchip patterns by the DiversiLab dendrogram system and similarity percentages as a guide, 28 isolates had concordant serotypes. A further set of six were correctly classified as one of two very closely related serotypes (Hadar or Istanbul). Six other isolates showed no match to the database (similarity values <95%) and these proved to be serotypes not included in the library. The serological identification of two isolates was not concordant with the rep-PCR predicted serotype at the 95% similarity threshold. Both discrepant samples, identified by traditional methods as Bredeney and Lille, are relatively rare and graph overlays with the top library match showed distinct amplification product differences. Conclusion: Since traditional serotyping methodology can take several days to provide serotype information, the DiversiLab System holds promise as a more rapid and highly reliable serotype identification system for members of this group.