Salmonella Dublin

Background: Salmonella enterica subsp. enterica serovar Dublin (antigenic formula 1,9,12[Vi]:g,p:-) is a serovar of the O:9 (D₁) serogroup. Serovar Dublin is a serovar adapted to cattle, which is the primary host, but it can also infect and cause disease in different hosts, including humans. In cattle, serovar Dublin causes acute and subclinical disease; symptoms of salmonellosis in cattle include: fever, diarrhea, abortions, respiratory signs (especially in calves), and systemic disease, thus making serovar Dublin an important economic concern in the bovine industry. Serovar Dublin is a zoonosis that causes one of the highest rates of systemic disease among all non-typhoidal salmonellosis cases in humans. Similar to Salmonella Choleraesuis, serovar Dublin infections in humans were linked to a higher incidence of bacteremia (91%), metastatic infections (30%), and mortality rates (26%) compared to other non-typhoidal Salmonella serovars. In the U.S., S. Dublin is the second most common Salmonella serovar among clinical non-human sources.

NCBI PD link for serovar Dublin: https://www.ncbi.nlm.nih.gov/pathogens/isolates/#(taxgroup_name:%22Salmonella%20enterica%22)%20AND%20computed_types:(%22serotype=Dublin%22)

Genetic characteristics: In 2012, the Animal Health Diagnostic Center at Cornell University published an animal health advisory that indicated an increase in the isolation of multidrug resistant strains of serovar Dublin in New York. Among ceftriaxone-resistant Salmonella isolates reported by the National Antimicrobial Resistance Monitoring System (NARMS), serovar Dublin represents the 40.8% and 2.9% of isolates from cattle and humans, respectively. Salmonella Dublin was identified as a monophyletic serovar with its largest lineage (Dublin 2-3) containing clonal sub-clades enriched for human isolates. Wallis et al. suggested that the Salmonella virulence plasmid does not play a role in the enteric phase of infection or the systemic spread of S. dublin; however, it likely facilitates the bacterium's persistence at systemic sites. Meanwhile, Libby et al. found that calves infected with the wild type or the complemented spvR mutant rapidly developed severe diarrhea and became moribund, whereas those infected with the spvR mutant exhibited little to no clinical signs of systemic salmonellosis and only mild diarrhea, indicating the spv genes of S. dublin facilitate increased intracellular proliferation within intestinal tissues and at extraintestinal sites in cattle. Mohammed et al. claimed that several virulence factors such as Gifsy-2 prophage, SPI-6, SPI-19, ggt and PagN in the genome of S. Dublin may contribute to its ability to invade the human bloodstream; however, no specific genomic markers distinguish invasive from non-invasive isolates, indicating that the host immune response likely plays a critical role in determining the clinical outcome of S. Dublin infection.

Animal reservoir: Cattle is the reservoir of this serovar, but it can cause disease in other animals, such as dogs, as well.

Geographical distribution: Serovar Dublin has been reported worldwide such as the US and the UK.

Animal outbreaks:

Year	Location	Breed	Number of cases
2000	Denmark	Mustela vison	25 mink and fox farms¹

¹ Each farm typically houses around 1,000 breeding females.

Human outbreaks: Several reports of outbreaks associated with Salmonella Dublin in humans have been documented. These outbreaks are primarily linked to the consumption of raw milk or products made from raw milk. Below are examples.

Year	Location	Associated source	Number of cases
2019	US: multistate	Ground beef	13
2015-2016	France	Raw-milk cheese	83
1989	England and Wales	Unpasteurized cows' milk cheese	42
1979	Glasgow	Milk	At least 700

Border rejections:

Year	Exporting country	Importing country	Associated source	Product category
2023	Italy	Finland	Frozen beef patties	Meat and meat products (other than poultry)
2023	Poland	Estonia	Frozen beef brisket	Meat and meat products (other than poultry)
2021	Denmark	Finland	Chilled beef trimmings	Meat and meat products (other than poultry)

Recalls:

Year	Location	Recalled food	Type
2020	France	Morbier au lait cru¹	Milk and milk products
2019	US: multistate	Ground beef²	Meat and meat products (other than poultry)

¹ France issued a press release with a public warning, while Spain announced a withdrawal of the product from the market.

² Central Valley Meat Co. in Hanford, California, issued a recall of 34,222 pounds of ground beef that may be contaminated with Salmonella Dublin. This recall was caused by a multistate outbreak of Salmonella Dublin infections linked to ground beef which was described above.

Relevant links:

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Salmonella Dublin