S. Choleraesuis¶

At a Glance


Antigenic Formula	`6,7:c:1,5`
Serogroup	O:7 (C1)
NCBI Pathogen Detection	View isolates

Background Information¶

Salmonella enterica subsp. enterica serovar Choleraesuis has the antigenic formula 6,7:c:1,5 of the O:7 (C₁) serogroup. Within S. Choleraesuis there are two biovars, S. Choleraesuis var. Kunzendorf and S. Choleraesuis var. Decatur. S. Choleraesuis is utilized as an H₂S negative QC strain in the USDA Microbiology Laboratory Guidebook, Chapter 4: Isolation and Identification of Salmonella from Meat, Poultry, Pasteurized Egg, Siluriformes (Fish) Products, Carcass and Environmental Sponges. S. Choleraesuis was one of the first types of Salmonella discovered. Theobald Smith and Daniel Salmon discovered S. Choleraesuis in 1885 while studying swine diseases. This serovar is highly host adapted to swine and causes swine paratyphoid. Pigs that have been infected can shed the organism for up to 12 weeks resulting environmental contamination and spread of the disease among the herd. Human cases from this serovar in the United States are rare, but nearly half of infections are invasive and can be severe. While it is not one of the leading serovars associated with nontyphoidal salmonellosis (NTS), S. Choeraesuis is one of the top servors implicated in NTS fatalities. In the 1990s, S. Choleraesuis was one of the top 10 serovars isolated from human cases inTaiwan. Improvements in swine husbandry, including vaccination of pigs, has substantially reduced the occurrence of Choleraesuis in Taiwan. Outbreaks from consuming contaminated pork are rare.

Table 1: Differention of serovars with antigenic formula 6,7:c:1,5

	Dulcitol	H₂S	Mucate	Agglutination of H:c in sera
S1	S2	S3
Paratyphi C (Vi^₊or Vi^-)	+	+	-	-
Choleraesuis	-	-	-	-
Choleraesuis var. Kunzendorf	-	+	-	-
Choleraesuis var. Decatur	+	+	+	+
Typhisuis	-	-	-	-

Genetic Characteristics¶

Serovar Choleraesuis has been found to be polyphyletic with four lineages identified. The majority of Salmonella Choleraesuis strains linked to human infections, particularly in Asian countries, exhibit MDR. This resistance is often attributed to traditional mobile genetic elements, such as transposons and plasmids, as well as integrative elements. These elements facilitate the dissemination of antimicrobial resistance genes within the bacterial genome via gene cassettes through site-specific recombination. Salmonella Choleraesuis in pigs harbors a 50-kb virulence plasmid including the spv operon. The spv operon is essential for the systemic phase of infection in certain hosts, with the virulence plasmid size being serotype-specific. The strains were cleared of a 50-kb virulence plasmid and exhibited significantly higher 50% lethal doses (LD50) in mice.

Animal Reservoir¶

Swine is the reservoir of this serovar.

Geographical Distribution¶

Serovar Choleraesuis has been reported worldwide. Although Salmonella Derby is rarely detected in human cases in the United States and European regions, it is the main cause of salmonellosis in several Asian countries such as Thailand and Taiwan.

Animal outbreaks: Multiple swine outbreaks linked to serovar Choleraesuis have been reported. Below are examples.

Year	Location	Breed	Number of cases
2020-2021	Sweden	Sus scrofa & Sus scrofa domesticus	Five domestic pig herds and one estate with a small group of fenced wild boar
2018-2019	Slovenia	Sus scrofa domesticus	2500 sows and approximately 20 breeding boars
2012-2013	Denmark	Sus scrofa domesticus	Four herds
1999-2000	Denmark	Sus scrofa domesticus	One herd

Border Rejections¶

There have been no recent border rejections linked to this serovar.

Recalls¶

Year	Location	Recalled food	Type
2021	Italy	Salami	Meat and meat products (other than poultry)