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Background: Salmonella enterica subsp. enterica serovar Hadar (antigenic formula 6,8:z10z₁₀:e,n,x) is a serovar of the O:8 (C₂-C₃) serogroup. S. Hadar is a common serovar in the U.S. and Europe. Serovar Hadar is associated with turkey and other birds, and is commonly found in ground turkey and chicken meat. In Europe,  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 S. Hadar.  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 4^th 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 S. serovar Hadar emergence, a phage typing scheme was developed, this included 35 included 24 recognized phage types. In 2011, The strain isolated from an outbreak associated with turkey burgers occurred in the U.S. , the outbreak strain 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.

Rep strainv 

Animal reservoir: The main reservoirs of S. Hadar serovar Hadar are turkey flocks and turkey meat. However, chickens, ducks and swine are also sources of this serovar. In the U.S, this serovar is the most common serovar isolated from turkey. 

Geographical distribution: S. Serovar Hadar has been isolated in the U.S., where it is among the top ten serovars from non-clinical non-human sources. In Europe, serovar Hadar is the 4^th most common serovar isolated from humans. In two countries of Asia, Thailand and China, this serovar has also been reported. In Thailand, serovar Hadar was reported in food (chicken and duck meat). Reports of acquisition of S. Hadar in travelers returning from Africa suggest a distribution of this serovar in Africa.reported worldwide such as the US. 

Human outbreaks: There were multiple human outbreaks of Salmonella Hadar. Below are examples.  Human outbreaks: Outbreaks of Salmonella Hadar have been identified in the U.S. and Europe

Border rejections:

¹ Salmonella Hadar and Kottbus were both found. 

Recalls:

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//webgate.ec.europa.eu/rasff-window/screen/notification/468397
5. https://www.fsis.usda.gov/recalls?keywords=Salmonella&page=1
6. https://webgate.ec.europa.eu/rasff-window/screen/notification/431922
7. .frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2025.1547190/full
8. https://pmc.ncbi.nlm.nih.gov/articles/PMC9152617/
9. https://academic.oup.com/femsle/article/218/1/127/532259
10. https://www.cdc.gov/salmonella/php/data-research/reptdk01.html
11. https://pmc.ncbi.nlm.nih.gov/articles/PMC11384159/#:~:text=Historically%2C%20outbreaks%20of%20foodborne%20Salmonella,to%20the%20backyard%20poultry%20market.
12. 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.
13. https://archive.cdc.gov/#/details?q=https://www.cdc.gov/salmonella/hadar-live-poultry-07-12/index.html&start=0&rows=10&url=httpshttp://www.cdc.gov/salmonella/hadar-live-poultry-07-12/index.html
14. httphttps://web.archive.org/web/20140122214727/https://www.cdc.gov/salmonella/hadar0411/040411/index.html
15. httphttps://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(05)70209-7.pdf
16. https://pubmed.ncbi.nlm.nih.gov/pmc/articles/PMC1601188/pdf/brmedj00016-0007.pdf/11078117/#:~:text=In%20August%201997%2C%20an%20outbreak,had%20symptoms%20of%20acute%20gastroenteritis.
17. https://pubmed.ncbi.nlm.nih.gov/9517880/
18. https://webgate.ec.europa.eu/rasff-window/screen/notification/468397
19. https://www.fsis.usda.gov/recalls?keywords=Salmonella&page=1
20. https://webgate.ec.europa.eu/rasff-window/screen/notification/431922