RESUMEN
Salmonella enterica subsp. enterica serovar Bovismorbificans has caused multiple outbreaks involving the consumption of produce, hummus, and processed meat products worldwide. To elucidate the intra-serovar genomic structure of S. Bovismorbificans, a core-genome analysis with 2690 loci (based on 150 complete genomes representing Salmonella enterica serovars developed as part of this study) and a k-mer-binning based strategy were carried out on 95 whole genome sequencing (WGS) assemblies from Swiss, Canadian, and USA collections of S. Bovismorbificans strains from foodborne infections. Data mining of a digital DNA tiling array of legacy SARA and SARB strains was conducted to identify near-neighbors of S. Bovismorbificans. The core genome analysis and the k-mer-binning methods identified two polyphyletic clusters, each with emerging evolutionary properties. Four STs (2640, 142, 1499, and 377), which constituted the majority of the publicly available WGS datasets from >260 strains analyzed by k-mer-binning based strategy, contained a conserved core genome backbone with a different evolutionary lineage as compared to strains comprising the other cluster (ST150). In addition, the assortment of genotypic features contributing to pathogenesis and persistence, such as antimicrobial resistance, prophage, plasmid, and virulence factor genes, were assessed to understand the emerging characteristics of this serovar that are relevant clinically and for food safety concerns. The phylogenomic profiling of polyphyletic S. Bovismorbificans in this study corresponds to intra-serovar variations observed in S. Napoli and S. Newport serovars using similar high-resolution genomic profiling approaches and contributes to the understanding of the evolution and sequence divergence of foodborne Salmonellae. These intra-serovar differences may have to be thoroughly understood for the accurate classification of foodborne Salmonella strains needed for the uniform development of future food safety mitigation strategies.
RESUMEN
The detection of Salmonella in spices is challenging due to the presence of antibacterial components. In this study, we evaluated the use of an adsorbent beta zeolite in pre-enrichment media to improve the recovery of Salmonella from cinnamon bark and oregano leaves. Samples (25 g) were spiked with varying levels of S. Montevideo or S. Senftenberg. After 2 weeks of stabilization at RT, betazeolite was added to cinnamon and oregano samples prior to the addition of 225 mL or 475 mL of pre-enrichment media, respectively. Detection sensitivity and rate of the test method were compared to the FDA Bacteriological Analytical Manual (BAM) method which requires the use of 2.5 L pre-enrichment broth. While Salmonella could not be detected in the test method using the reduced volume of pre-enrichment media alone, the addition of beta zeolite resulted in a positivity rate of 62% and 72.6% for cinnamon bark and oregano leaves respectively (all spike levels and both serovars combined). Furthermore, while there were differences in the LOD50 compared to the BAM method, there was no significant difference in the minimum level of detection between the betazeolite and the BAM methods. Our results demonstrate that the use of betazeolite in the pre-enrichment media offers a method with reduced media volumes without compromising on the sensitivity or efficiency of Salmonella detection in cinnamon bark and oregano leaves.