Cross-species genomic analysis of <i>Salmonella enterica</i> subspecies <i>enterica</i> serovar Dublin isolated from dairy cattle, dogs, and humans in Florida from 2019 to 2024.
This study highlights the interconnectedness of S. Dublin infections in humans and animals, emphasizing the need for responsible antimicrobial use and genomic surveillance.
Where it sits
this study against the rest of the ll-37 corpusSummary and findings
This study analyzed 78 clinical strains of Salmonella enterica serovar Dublin isolated from humans, dairy cattle, and dogs in Florida from 2019 to 2024. The analysis focused on antimicrobial resistance (AMR) gene profiling and genomic relatedness across host species. Findings included widespread multidrug resistance and conserved virulence genes across all isolates.
Abstract
<i>Salmonella enterica</i> serovar Dublin (<i>S.</i> Dublin) is a cattle-adapted pathogen that can cause severe systemic infections in humans and animals. Understanding genomic relatedness across host species is essential for assessing the zoonotic potential and dissemination of antimicrobial resistance (AMR). In this study, 78 clinical <i>S.</i> Dublin strains, isolated in Florida between 2019 and 2024, were subjected to comparative genomic analysis. These included 19 animal-derived isolates (17 from dairy cattle and two from dogs) and 59 human-derived isolates. AMR gene profiling revealed widespread multidrug resistance, with genes conferring resistance to aminoglycoside (<i>aac(6')-Iaa</i>, <i>aph(6)-Id</i>), tetracycline (<i>tetA</i>), and sulfonamide (<i>sul2</i>) detected in all isolates. Beta-lactamase genes, particularly <i>bla</i> <sub>TEM</sub> variants, were detected more frequently in human- and dog-derived isolates than in cattle-derived isolates. In contrast, rare <i>bla</i> <sub>CMY</sub> variants (<i>bla</i> <sub>CMY-61</sub>, <i>bla</i> <sub>CMY-130</sub>, <i>bla</i> <sub>CMY-153</sub>, and <i>bla</i> <sub>CMY-2b</sub>) were detected in only one cattle isolate. Plasmid analysis revealed that IncX1, IncFII(S), and IncC replicons were common among the isolates, highlighting their potential role in facilitating AMR dissemination via horizontal gene transfer. Virulence gene profiling revealed conserved <i>Salmonella</i> pathogenicity islands, type III and type VI secretion systems, and the <i>spv</i> operon across <i>S</i>. Dublin isolates from all host species. Multilocus sequence typing (MLST) confirmed that all isolates belonged to sequence type (ST) 10, and most harbored the Gifsy-2 prophage. The SNP-based phylogeny revealed distinct host-associated clades as well as mixed-host clusters, demonstrating close genomic relatedness among isolates from different host species and suggesting possible cross-species transmission, exposure to shared sources, or circulation of closely related lineages. These findings illustrate the interconnectedness of animal and human <i>S.</i> Dublin infections, emphasize the importance of responsible antimicrobial use, and highlight the value of genomic surveillance for detecting and controlling <i>S</i>. Dublin infections. Collectively, this study provides a genomic framework for assessing cross-species relatedness, virulence characteristics, and AMR patterns of <i>S.</i> Dublin.
Background
This paper addresses the genomic relatedness of Salmonella enterica serovar Dublin across different host species, focusing on its zoonotic potential and antimicrobial resistance. Prior studies have established S. Dublin as a significant pathogen in both animals and humans, but the cross-species transmission dynamics remain unclear. Understanding these relationships is crucial for public health and effective antimicrobial stewardship.
Methods
The study involved comparative genomic analysis of 78 clinical S. Dublin strains isolated in Florida from 2019 to 2024. The population included 19 isolates from animals (17 from dairy cattle and 2 from dogs) and 59 from humans. The analysis included AMR gene profiling, virulence gene profiling, and multilocus sequence typing (MLST) to assess genomic relatedness.
Results
All isolates exhibited multidrug resistance, with AMR genes present in every strain. Beta-lactamase genes were more prevalent in human- and dog-derived isolates compared to cattle-derived ones. MLST confirmed that all isolates belonged to sequence type (ST) 10, indicating a close genetic relationship among strains from different hosts.
Interpretation
The findings align with previous research indicating significant genetic overlap among S. Dublin strains from various hosts. While the statistical significance of the observed AMR patterns is noted, the clinical relevance of these findings requires further investigation, particularly regarding the implications for treatment and infection control. Limitations include potential confounding factors such as small sample size and the lack of longitudinal data.
Key findings
- 78 clinical S. Dublin strains analyzed, including 19 animal-derived and 59 human-derived isolates.
- AMR genes conferring resistance to aminoglycoside, tetracycline, and sulfonamide detected in all isolates.
- Beta-lactamase genes detected more frequently in human- and dog-derived isolates than in cattle-derived isolates.
- All isolates belonged to sequence type (ST) 10, with most harboring the Gifsy-2 prophage.
- Distinct host-associated clades and mixed-host clusters observed in SNP-based phylogeny.
Limitations
- small sample size of 78 strains
- focus on a single geographic region
- short study duration from 2019 to 2024
- potential for confounding factors in cross-species transmission analysis