Background: Salmonella enterica subsp. enterica serovar Hadar (antigenic formula 6,8:z10:e,n,x) is a serovar of the O:8 (C2-C3) serogroup. In Europe, this serovar emerged in 1971. In England, before 1971, only eight human cases reported; by 1979 a total of 1,600 human salmonellosis cases were confirmed to be caused by serovar Hadar. Serovar Hadar is among the top ten serovars from non-clinical non-human sources in the US. Also, this serovar is the most common serovar isolated from turkey in the US. In Europe, serovar Hadar is the 4th most common serovar isolated from humans. Reports of acquisition of serovar Hadar in travelers returning from Africa suggest a distribution of this serovar in Africa. 

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

Genetic characteristics: Serovar Hadar has been found to be polyphyletic with two lineages identified and two stand-alone singletons that do not cluster with any other Salmonella Hadar isolates. As a consequence of the serovar Hadar emergence, a phage typing scheme was developed, this included 24 recognized phage types. The strain isolated from an outbreak associated with turkey burgers occurred in the U.S. in 2011 showed resistance to several antibiotics commonly used to treat salmonellosis (ampicillin, amoxicillin/clavulanate, cephalothin, and tetracycline). Among 64 Hadar isolates collected from different patients from 2005 to 2010 in Switzerland, 71.8% of them showed resistance to nalidixic acid. While 40.6% of the isolates were resistant to the β-lactam antibiotic ampicillin, they remained sensitive to the third-generation cephalosporin cefotaxime. All Hadar strains Nógrády et al. analyzed showed profound growth suppression. Prior colonization of chickens with Hadar strain 18 effectively prevented superinfection by S. Enteritidis, Typhimurium, Virchow and Saintpaul. REPTDK01 is a REP (reoccurring, emerging, or persisting) strain of Salmonella Hadar that has been linked to illnesses and outbreaks in the United States.

Animal reservoir: The main reservoirs of serovar Hadar are turkey flocks and turkey meat. However, chickens, ducks and swine are also sources of this serovar. 

Geographical distribution: Serovar Hadar has been reported worldwide such as the US. 

Human outbreaks: There were multiple human outbreaks of Salmonella Hadar. Below are examples.  

Year

Location

Associated source

Number of cases

2021

US: multistate

Ground turkey

33

2012

US: multistate

Live poultry

46

2011

US: multistate

Turkey burgers

12

2005

Spain

Pre-cooked chicken

2138

1997

Italy

Roasted rabit

29

1994

Italy

Meat salad

448

Border rejections:

Year

Exporting country

Importing country

Associated source

Product category

2021Hungary ItalyDuck fillets1Poultry meat and poultry meat products

1 Salmonella Hadar and Kottbus were both found. 

Recalls:

YearLocationRecalled foodType
2021USGround turkey1Poultry meat and poultry meat products
2020LatviaTurkey minced meat2Poultry meat and poultry meat products

1 Plainville Brands, LLC, issued the recall because of the Salmonella Hadar outbreak.

2 Product was (presumably) no longer on the market.    

Relevant links:

  1. https://pmc.ncbi.nlm.nih.gov/articles/PMC1601188/pdf/brmedj00016-0007.pdf
  2. https://www.cdc.gov/salmonella/pdf/hadar-508c.pdf
  3. https://www.sciencedirect.com/science/article/pii/S1198743X14622126
  4. https://pubmed.ncbi.nlm.nih.gov/3729881/
  5. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2025.1547190/full
  6. https://pmc.ncbi.nlm.nih.gov/articles/PMC9152617/
  7. https://academic.oup.com/femsle/article/218/1/127/532259
  8. https://www.cdc.gov/salmonella/php/data-research/reptdk01.html
  9. https://pmc.ncbi.nlm.nih.gov/articles/PMC11384159/#:~:text=Historically%2C%20outbreaks%20of%20foodborne%20Salmonella,to%20the%20backyard%20poultry%20market.
  10. https://archive.cdc.gov/www_cdc_gov/salmonella/hadar-04-21/details.html#:~:text=As%20of%20May%2017%2C%202021%2C%20a%20total%20of%2033%20people,No%20deaths%20were%20reported.
  11. https://archive.cdc.gov/#/details?q=https://www.cdc.gov/salmonella/hadar-live-poultry-07-12/index.html&start=0&rows=10&url=https://www.cdc.gov/salmonella/hadar-live-poultry-07-12/index.html
  12. https://web.archive.org/web/20140122214727/https://www.cdc.gov/salmonella/hadar0411/040411/index.html
  13. https://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(05)70209-7.pdf
  14. https://pubmed.ncbi.nlm.nih.gov/11078117/#:~:text=In%20August%201997%2C%20an%20outbreak,had%20symptoms%20of%20acute%20gastroenteritis.
  15. https://pubmed.ncbi.nlm.nih.gov/9517880/
  16. https://webgate.ec.europa.eu/rasff-window/screen/notification/468397
  17. https://www.fsis.usda.gov/recalls?keywords=Salmonella&page=1
  18. https://webgate.ec.europa.eu/rasff-window/screen/notification/431922
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