Evaluation of PCR inhibitory effect of enrichment broths and comparison of DNA extraction methods for detection of Salmonella Enteritidis using real-time PCR assay

The best enrichment broth and DNA extraction scheme was determined for rapid and sensitive detection of Salmonella Enteritidis in steamed pork using real-time PCR. The inhibitory effect of commonly used Salmonella enrichment broths, Rappaport-Vassiliadis (RV) and Muller-Kauffmann tetrathionate with novobiocin (MKTTn), on real-time PCR was confirmed. The inhibition of PCR was statistically significant (p < 0.05) in RV and MKTTn, as compared with buffered peptone water (BPW) or phosphate-buffered saline. The inhibitory effect of the selective enrichment media was successfully removed by using a modified DNA extraction, PrepMan Ultra Reagent with an additional washing step or the DNeasy Tissue Kit. In three experiments, when applied to detection of Salmonella Enteritidis in steamed pork, the real-time PCR coupled with single 24 h enrichment with BPW performed better than double 48 h enrichment with BPW plus RV or MKTTn. The simple real-time PCR assay using BPW proved to be a rapid and sensitive test for detection of low concentrations of Salmonella Enteritidis in steamed pork samples as compared with the conventional culture method.

Identification of 1,531 cSNPs from Full-length Enriched cDNA Libraries of the Korean Native Pig Using in Silico Analysis

Sequences from the clones of full-length enriched cDNA libraries serve as valuable resources for functional genomics related studies, genome annotation and SNP discovery. We analyzed 7,392 high-quality chromatograms (Phred value >30) obtained from sequencing the 5' ends of clones derived from full-length enriched cDNA libraries of Korean native pigs including brainstem, liver, cerebellum, neocortex and spleen libraries. In addition, 50,000 EST sequence trace files obtained from GenBank were combined with our sequences to identify cSNPs in silico. The process generated 11,324 contigs, of which 2,895 contigs contained at least one SNP and among them 610 contigs had a minimum of one sequence from Korean native pigs. Of 610 contigs, we randomly selected 262 contigs and performed in silico analysis for the identification of cSNPs. From the results, we identified 1,531 putative coding single nucleotide polymorphisms (cSNPs) and the SNP detection frequency was one SNP per 465 bp. A large-scale sequencing result of clones from full-length enriched cDNA libraries and identified cSNPs will serve as a useful resource to functional genomics related projects such as a pig HapMap project in the near future