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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 very common serovar in the U.S. and Europe; associated with turkey and other birds, it is commonly found in ground turkey and chicken meat. In Europe  In Europe, this serovar emerged in the 1971. In England, for example, before 1971 were , only eight human cases reported, but ; by 1979 a total of 1,600 human salmonellosis human cases were confirmed to be caused by S. Hadar.  Consequent to the S. 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 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 typically 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 The main reservoirs for S. Hadar of serovar Hadar are turkey flocks and turkey meat. However, chickens, ducks and swine are also source sources of this serovar. In the U.S this serovar is the most common serovar isolated from turkey. 

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

Human outbreaks: There were multiple human outbreaks of Salmonella Hadar. Below are examples.  Outbreaks: outbreaks of Salmonella Hadar have been identified in the U.S. and Europe, one large outbreak with > 2,000 cases was reported in Spain.

Border rejections:

¹ Salmonella Hadar and Kottbus were both found. 

Recalls:

Relevant links:

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=httpshttp://www.cdc.gov/salmonella/hadar-live-poultry-07-12/index.html
12. httphttps://web.archive.org/web/20140122214727/https://www.cdc.gov/salmonella/hadar0411/040411/index.html
13. httphttps://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(05)70209-7.pdf
14. https://pubmed.ncbi.nlm.nih.gov/pmc/articles/PMC1601188/pdf/brmedj00016-0007.pdf11078117/#:~: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