Characterizing Antimicrobial Resistance Genes, Virulence Genes, and Plasmids in Isolates of Salmonella Dublin Obtained Via FoodNet

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Restricted (Penn State Only)
Author:
Mackley, Jasmine
Area of Honors:
Immunology and Infectious Disease
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Erika Ganda, Thesis Supervisor
Robert Paulson, Thesis Honors Advisor
Keywords:
Salmonella Dublin
Salmonella
FoodNet
antimicrobial resistance
One Health
microbiome
Abstract:
This study addresses the growing issue of human cases of Salmonella enterica subsp. enterica serotype Dublin (Salmonella Dublin) by characterizing demographic information, genotypic profile, and phylogeny of strains compiled by the United States Center for Disease Control and Prevention’s Foodborne Diseases Active Surveillance Network (FoodNet). The study included 104 human samples of Salmonella Dublin collected from 2014 through 2022, including samples from all ten FoodNet collaboration states. A high proportion of the included cases (72.12%) was among individuals 50 years old and older. Isolates were derived from diverse sample types, with blood (47/104), stool (32/104), and urine (15/104) being the most common. Various antimicrobial resistance genes (including golS, golT, mdsA, and mdsB) were identified in all the analyzed strain genomes. The isolate genomes included 109 distinct virulence genes, with the majority (104/109) being found in over 99% of the analyzed genomes. Additionally, seven plasmids (IncX1, IncFII/S, ColRNAI, IncA/C2, IncFIA, IncFIB/pB171, and IncI1_1_Alpha) were present in the strain genomes. Phylogenetic analysis revealed sporadic clustering based on strains’ collection year, collection state, and sample type, including one cluster of 13 closely related samples that were traced to the same outbreak based on the associated metadata. Also, based on full genome annotation of the strains, there was a statistically significant difference between strains from blood and stool sample types. Overall, this project provides valuable insights regarding the antimicrobial resistance genes, virulence genes, and plasmids associated with strains of Salmonella Dublin. Additionally, this study showcases the value of active surveillance networks such as FoodNet, as well as the importance of using a One Health approach to address bacteria such as Salmonella Dublin. This study’s results can be used to guide treatment practices and to develop public health interventions against this increasingly important pathogen.