Background: Salmonella enterica subsp. enterica serovar Chester (antigenic formula: 1,4,[5],12:e,h:e,n,x) is a serovar of the O:4 (B) serogroup. In 1937, this serovar was first isolated from humans during a food poisoning outbreak in the hospital of Chester, United Kingdom. Serovar Chester is a rare serovar worldwide. For example, in Canada, it only accounted for an average of seven human infections per year. In the US during 2001-2011, only 403 human cases have been reported. In addition, animal and food surveillance have not found serovar Chester in these sources in the US. 

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

Genetic characteristics: Serovar Chester has been found to be polyphyletic with two lineages identified. Multidrug resistance was identified in two isolates of serovar Chester (ST2063), which harbored resistance determinants across five distinct classes of antibiotics. Whole genome sequencing of serovar Chester in Norway revealed four geographically distinct clusters. All isolates within the African cluster exhibited resistance to at least one class of antimicrobials, whereas resistance was uncommon in the other clusters.

Animal reservoir: There is not clear evidence of the animal reservoir for this serovar, although serovar Chester has been found in various animals, including turkeys, cattle, reptiles, and birds. 

Geographical distribution: Serovar Chester have been reported worldwide, including countries in North (US, Canada) and South America (Brazil), Morocco and Australia.

Human outbreaks: Despite the fact that this is a rare serovar, multiple outbreaks have been reported. Below are examples. 

Year

Location

Associated source

Number of cases

2010

Canada

Headcheese

33

2010

US: multistate

Frozen meals

44

2005

Australia

Tap water

26

1998

Australia

Turtle meat

36

Border rejections:

Year

Exporting country

Importing country

Associated source

Product category

2023SpainFranceFrozen chicken drumstick1Poultry meat and poultry meat products
2023TurkeySwitzerlandRed Paprika, sweetHerbs and spices
2021The United KingdomDenmarkFishmeal pellets for farmed salmon Feed materials

1 Salmonella Vichow and Salmonella Chester were both found. 

Recalls:

YearLocationRecalled foodType
2024GermanyOrganic moringa powder from Sri LankaDietetic foods, food supplements and fortified foods

Relevant links:

  1. https://pmc.ncbi.nlm.nih.gov/articles/PMC5322187/#r16
  2. https://web.archive.org/web/20120822142907/http://www.nml-lnm.gc.ca/NESP-PNSME/index-eng.htm
  3. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2025.1547190/full
  4. https://pubmed.ncbi.nlm.nih.gov/31099590/#:~:text=Among%20the%2033%20chicken%20isolates,;%20surveillance;%20whole%20genome%20sequencing.
  5. https://pmc.ncbi.nlm.nih.gov/articles/PMC6352000/
  6. https://www.sciencedirect.com/science/article/pii/S0362028X23014473#bb0010
  7. https://pubmed.ncbi.nlm.nih.gov/22488063/
  8. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6248a2.htm
  9. https://www1.health.gov.au/internet/main/publishing.nsf/content/cda-cdi3003-pdf-cnt.htm/$FILE/cdi3003b.pdf
  10. https://pubmed.ncbi.nlm.nih.gov/10774704/
  11. https://webgate.ec.europa.eu/rasff-window/screen/notification/638548
  12. https://webgate.ec.europa.eu/rasff-window/screen/notification/598996
  13. https://webgate.ec.europa.eu/rasff-window/screen/notification/506373
  14. https://webgate.ec.europa.eu/rasff-window/screen/notification/675850
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