U.S. flag

An official website of the United States government

Ag Data Commons migration begins October 18, 2023

The Ag Data Commons is migrating to a new platform – an institutional portal on Figshare. Starting October 18 the current system will be available for search and download only. Submissions will resume after the launch of our portal on Figshare in November. Stay tuned for details!

Comparison of methods to detect low levels of Salmonella enterica in surface waters to support antimicrobial resistance surveillance efforts performed in multiple laboratories

    Identifying and developing effective and sensitive detection methods for antimicrobial resistant Salmonella enterica from surface water is a goal of the U.S. National Antimicrobial Resistance Monitoring System (NARMS). No specific microbiological methods used in surveillance efforts for Salmonella enterica or antimicrobial resistant S. enterica in water have been standardized or reported in the U.S. Here we describe a multi-laboratory evaluation of four methods, bulk water enrichment (BW), vertical Modified Moore Swab (VMMS), modified Standard Method 9260.B3 (SM), and dead-end ultrafiltration (DEUF), to recover S. enterica from surface water.

    IncA-C Alignment

      IncA/C plasmids are a class of plasmids from Enterobacteraciae that are relatively large (49 to >180 kbp), are readily transferred by conjugation, and carry multiple antimicrobial resistance genes. Reconstruction of the phylogeny of these plasmids has been difficult because of the high rate of remodeling by recombination-mediated horizontal gene transfer (HGT). We hypothesized that evaluation of nucleotide polymorphisms relative to the rate of HGT would help to develop a clock to show if anthropic practices have had significant influences on the lineages of the plasmid. A system was developed to rapidly sequence up to 191 known open27 reading-frames from each of 39 recently isolated IncA/C plasmids from a diverse panel of Salmonella enterica and Escherichia coli. With these data plus sequences from Genbank we were able to distinguish six distinct lineages that had extremely low numbers of polymorphisms within each lineage, especially among the largest group designated as Lineage 1. Two regions, each about half the plasmid in size, could be distinguished with a separate lineal pattern. The distribution of Lineage 1 showed that it has migrated extremely rapidly with fewer polymorphisms than can be expected in two-thousand years. Remodeling by frequent HGT was evident with a pattern that appeared to have the highest rate just upstream of the putative conjugation origin of transfer (ori-T). It seems likely that when an IncA/C plasmid is transferred also adjacent to a multiple antimicrobial resistance gene cassette.

      Vaccination Against Lawsonia intracellularis Decreases Shedding of Salmonella enterica serovar Typhimurium in Co-Infected Pigs and Alters the Gut Microbiome

        *Salmonella enterica* is a leading cause of foodborne illness worldwide and pork can serve a source of infection. In this study, we investigated if vaccinating pigs against L*awsonia intracellularis*, a common pathogen of swine that has previously been shown to favor *Salmonella enterica* infection, confers protection against *Salmonella enterica serovar Typhimurium*. We investigated the underlying changes in the gut microbiome mediated by single *S. Typhiumurium* infection compared to co-infection with *L. intracellularis* as well as the effect of vaccination on the microbiome.

        Changes in the Porcine Intestinal Microbiome in Response to Infection with Salmonella Enterica and Lawsonia Intracellularis

          Salmonella enterica is a leading cause of food borne illness. Recent studies have shown that S. enterica is a pathogen capable of causing alterations to the composition of the intestinal microbiome. A recent prospective cross-sectional study of French pork production farms found a statistically significant association between Lawsonia intracellularis and carriage of S. enterica. The ZIP file includes 51 sequence files (FASTA format) and 1 Excel file describing the species, age, sampled tissue, treatment condition, and sample name corresponding to the different file names. The Excel file is converted to a csv for archival purposes. The Readme.txt file describes the context of how the data was created and any codes used in the spreadsheet.