Background: 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 in Taiwan. Improvements in swine husbandry, including vaccination of pigs, has substantially reduced the occurrence of Choleraesuis in Taiwan. Outbreaks from consuming contaminated pork are rare.
The in-silico serotyping tool SeqSero2, which is used by NCBI PD, cannot differentiate between Salmonella Paratyphi C, Choleraesuis, or Typhisuis because there are also two other serovoars with the same antigenic formula as S. Choleraesuis: S. Paratyphi C. and S. Typhisuis. Additional markers are required to accurately determine the serotype of Choleraesuis. Differentiation is accomplished through biochemical analysis, see Table 1 below. NCBI PD link for serovar Paratyphi C or Choleraesuis or Typhisuis: https://www.ncbi.nlm.nih.gov/pathogens/isolates/#(taxgroup_name:%22Salmonella%20enterica%22)%20AND%20computed_types:(%22serotype=Paratyphi%20C%20or%20Choleraesuis%20or%20Typhisuis%22)
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:
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) |
Relevant links: