A study conducted by Penn State University researchers has demonstrated the potential for Salmonella Dublin, which is primarily associated with infections in cows, to persist in the environment and spread to humans. The researchers say the finding is especially relevant to public health as antimicrobial resistance (AMR) among S. Dublin has been on the rise.

Based on their findings, the researchers emphasize the need for a “One Health” approach to addressing the spread of drug-resistant S. Dublin among cows, humans, and the environment.

“Humans usually get infected by eating contaminated beef, milk or cheese, but direct contact with cattle by farm workers, for example, is also a risk,” said Erika Ganda, Ph.D., Associate Professor of Food Animal Microbiomes in the Penn State College of Agricultural Sciences and corresponding author on the study. “This study shows that to tackle antibiotic-resistant S. Dublin, we must use a One Health approach—looking at how humans, animals and the environment are interconnected in the spread and evolution of this dangerous pathogen.”

For the study, published in Applied and Environmental Microbiology, the researchers analyzed 2,150 S. Dublin isolates from 581 cow clinical samples, 644 human clinical samples, and 905 environmental samples, including post-harvest beef and dairy food samples and on-farm environmental swabs. The sampling data was accessed via the U.S. National Center for Biotechnology Information (NCBI) Pathogen Isolate Browser, which houses whole-genome sequencing (WGS) data, and the U.S. National Antimicrobial Resistance Monitoring System (NARMS) database, which monitors AMR in foodborne pathogens, covering the years 2002–2023.

Analysis of WGS data revealed that, despite some genetic differences across 2,150 strains of S. Dublin, the bacteria remained highly similar—indicating the potential for cross-transmission among cattle, humans, and the environment.

The researchers also found that certain AMR genes and plasmids carrying multidrug resistance (MDR) genes were most prevalent in cattle clinical isolates. The cattle clinical isolates also exhibited the greatest genetic diversity; however, the genomic core remained highly similar across all isolates, regardless of source.

Lead author Sophia Kenney, Ph.D., who was a postdoctoral scholar in the Department of Animal Science at the time of the study, remarked that the increasing MDR observed in some S. Dublin isolates is a concern. “It complicates treatment for both cattle and humans, but knowing the genetic trends of S. Dublin across multiple sources in the U.S. can better inform disease control and more targeted surveillance efforts,” she said.

Overall, the study’s findings create an understanding of the One Health dynamics of S. Dublin and provide detailed genetic evidence that can help guide surveillance and inform intervention strategies, such as limiting antibiotics use in livestock.

Nkuchia M’ikanatha, Dr.P.H., M.P.H., Lead Epidemiologist for the Pennsylvania Department of Health and an affiliated researcher in Penn State’s Department of Food Science, also contributed to the study.

The project was supported by the U.S. Department of Agriculture’s (USDA’s) National Institute of Food and Agriculture (NIFA) and USDA’s Plant Health Inspection Service (APHIS) National Bio and Agro-Defense Facility Scientist Training Program.