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Wiki Markup*{+}Background:+* _Salmonella enterica_ subsp. _enterica_ serovar Heidelberg (antigenic formula 1,4,\[5\],12:r:1,2) is a serovar of the O:4 (B) serogroup. _S_. Heidelberg is commonly found in poultry meat in North America. In the U.S. and Canada, it has caused numerous infections in chickens. In the U.S., this serovar has caused a number of outbreaks that included the recent outbreak (October, 2013), linked to [raw chicken|http://www.cdc.gov/salmonella/heidelberg-10-13/index.html]; this outbreak was caused by a multidrug resistant _S._ Heidelberg strain (resistant to ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline). _S._ Heidelberg accounts for the 8.6% of ceftriaxone-resistant _Salmonella_ isolated from humans in the U.S. Recently, a [phage typing scheme|http://jcm.asm.org/content/41/9/4279.full] was developed for serovar Heidelberg in Canada; this scheme recognizes 49 phage types.  

Animal reservoir: S. Heidelberg is mostly found in chickens and turkeys. 

Geographical distribution: Mostly reported from North America, serovar Heidelberg is the second and seventh most common serovar isolated from humans in Canada and in the U.S., respectively. In Europe this serovar is rare (approx. 180 cases/year).

Outbreaks: Multiple Heidelberg outbreaks have been linked to poultry, most of them in the U.S.

serogroup. Salmonella Heidelberg was first identified in 1933 in Heidelberg, Germany. It was later detected in the United States for the first time in 1954. In the United States, Salmonella Heidelberg ranks as the third most common serotype found in retail meat and food animal isolates. It is also among the top four serotypes isolated from blood samples. Notably, 12%–13% of Salmonella Heidelberg infections in North America result in invasive disease, a rate significantly higher than the U.S. average of 7% for all Salmonella infections.

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

Genetic characteristics: Serovar Heidelberg has been found to be monophyletic. Previously, a phage typing scheme was developed for serovar Heidelberg in Canada; this scheme recognizes 49 phage types. S. Heidelberg accounts for the 8.6% of ceftriaxone-resistant Salmonella isolated from humans in the U.S. SARA33 is a multidrug resistant (MDR) strain. This strain was found, in silico, Relevant genetic characteristics: Whole genome sequences for 15 strains of S. Heidelberg have been deposited at GenBank as of October, 2013. Genomic characteristics of the sequenced S. Heidelberg include i) a genome size ranging from 4.73 to 4.98 Mb, ii) a mol G+C% of 52.1 , and iii) 5,578 to 5,039 predicted genes. Many of these sequenced strains were implicated in recent outbreaks (2011 and 2012), in the U.S. Salmonella Heidelberg str. SARA33 is a multidrug resistant strain. This strain was found to contain a novel integron cassette; in addition, it was found to carry the following resistance genes: aac(6′)-ly, aadA5, aadB, aa(6′)-33, and aadA1, sul1 and sul2, blaOXAbla_OXA-2 and blaTEMbla_TEM, tetD. Resistance genes in S. Heidelberg have been identified in the chromosome (resistant islands) and in plasmids. The Different incompatibility types (A/C, FIB, HI2) have been identified in the plasmids that carried resistance genes represent different incompatibility types (IncA/C, IncFIB, IncHI2)in S. Heidelberg. A MDR S. Heidelberg strain (resistant to ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline) was found to cause a multistate outbreak linked to the Foster Farms brand chicken. Etter et al. analyzed a total of nine Heidelberg isolates collected during the outbreak investigation and revealed that (i) six Salmonella Heidelberg isolates linked to the foodborne outbreak exhibited increased heat tolerance, (ii) one of these heat-tolerant isolates also demonstrated enhanced biofilm formation under stressful conditions, (iii) heat stress triggered higher expression of multidrug efflux and virulence genes in Salmonella Heidelberg, and (iv) the outbreak-related isolates appeared to be transcriptionally prepared to better withstand processing stresses and potentially to cause infection.

Phylogenetic and pan-genomic analyses that included two of the sequenced S. Heidelberg strains and other Salmonella serovars concluded that S. Heidelberg (i) belongs to clade A, according to den Bakker et al. (2011) classification, (ii) appears to have a single evolutionary origin, and (iii) contains 74 gene families unique to this serovar.  

Genome sequences available:

Animal reservoir:Poultry, including chickens and turkeys, are the main reservoirs for serovar Heidelberg. It has also been found in other animals such as cattle, swine, and dogs.

Geographical distribution: Serovar Heidelberg has been reported worldwide, mainly in North America.

Human outbreaks: Multiple Heidelberg outbreaks have been linked to poultry, most of them in the US. Here are some example:

Border rejections:

Recalls:

¹ Tyson Foods, Inc. issued a recall of around 33,840 pounds of mechanically separated chicken products due to potential contamination with Salmonella Heidelberg. These products were manufactured on October 11, 2013, and distributed exclusively for institutional use across the nation.

Relevant links:

1. https://scholar.google.com/scholar_lookup?journal=J%20Bacteriol&title=About%20a%20new%20type%20of%20bacteria%20form%20the%20paratyphoid%20enteritis%20group&author=VH%20Habbs&publication_year=1933&pages=367-374&
2. https://www.jstor.org/stable/1588278?casa_token=sTneApEGY84AAAAA%3AxCcrraoy6aPu-M6ejq3MtxjBB1MMgP_Z6YwUi4_cVoYN9dHewNuMwxG9EeHAe6ua_dq1zAdT8vyzdTrmZ47-5_6uPGQhzNzzMViPBHNg6yfUnNVpvw&seq=1
3. https://pubmed
4. Salmonella enterica subsp. enterica serovar Heidelberg str. 41563 http://www.ncbi.nlm.nih.gov/assembly/481988/
5. Salmonella enterica subsp. enterica serovar Heidelberg str. 41565 http://www.ncbi.nlm.nih.gov/18757574/assembly
6. https:/482048/
7. Salmonella enterica subsp. enterica serovar Heidelberg str. 41566 http://www.ncbi.nlm.nih.gov/assembly/482028/
8. Salmonella enterica subsp. enterica serovar Heidelberg str. 41573 http://www.ncbi.nlm.nih.gov/assembly/482008/
9. Salmonella enterica subsp. enterica serovar Heidelberg str. 41578 http://www.ncbi.nlm.nih.gov/assembly/41121/
10. journals.asm.org/doi/10.1128/aac.01333-10
11. https://wwwnc.cdc.gov/eid/article/16/1/09-0729_article
12. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2025.1547190/full
13. https://journals.asm.org/doi/full/10.1128/jcm.41.9.4279-4284.2003
14. https://www.cdc.gov/salmonella/pdf/heidelberg-508c.pdf
15. https://pmcSalmonella enterica subsp. enterica serovar Heidelberg str. 41579 http://www.ncbi.nlm.nih.gov/assemblyarticles/481968PMC3790100/Salmonella enterica subsp. enterica serovar Heidelberg str. B182
16. httphttps://wwwpubmed.ncbi.nlm.nih.gov/23251446/assembly
17. https:/377398/
18. Salmonella enterica subsp. enterica serovar Heidelberg str. CFSAN002069 http://www.ncbi.nlm.nih.gov/assembly/41111/
19. journals.asm.org/doi/10.1128/aem.01065-19
20. https://bmcgenomics.biomedcentral.com/articles/10.1186/1471-2164-12-425
21. https://pmcSalmonella enterica subsp. enterica serovar Heidelberg str. CFSAN00322 http://www.ncbi.nlm.nih.gov/assemblyarticles/493148PMC3175032/Salmonella enterica subsp. enterica serovar Heidelberg str. CFSAN00325 http
22. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1282832/pdf#:~:text=Salmonella%20enterica%20subspecies%20enterica%20serovar%20Heidelberg%20(Salmonella%20Heidelberg)%20is%20primarily,Clothier%20and%20Byrne%2C%202016).
23. https://pmcncbi.nlm.nih.gov/assembly/493168/Salmonella enterica subsp. enterica serovar Heidelberg str. CFSAN00326 http://www.ncbi.nlm.nih.gov/assemblyarticles/493188PMC3768931/Salmonella enterica subsp. enterica serovar Heidelberg str. CFSAN00328 http
24. https://wwwpubmed.ncbi.nlm.nih.gov/assembly/493208/Salmonella enterica subsp. enterica serovar Heidelberg str. SARA33 http/34932458/#:~:text=We%20report%20a%20multistate%20Salmonella,indicators%20of%20severity%20and%20invasiveness.
25. https://archive.cdc.gov/#/details?url=https://www.cdc.gov/salmonella/heidelberg-11-16/index.html
26. https://archive.cdc.gov/www_cdc_gov/salmonella/heidelberg-10-13/index.html
27. https://archive.cdc.gov/www_cdc_gov/salmonella/2011/chicken-liver-1-11-2012.html
28. https://pubmedncbi.nlm.nih.gov/assembly/62751/Salmonella enterica subsp. enterica serovar Heidelberg str. SL476 http://www.ncbi.nlm.nih.gov/assembly/4174825865382/Salmonella enterica subsp. enterica serovar Heidelberg str. SL486
29. httphttps://wwwpmc.ncbi.nlm.nih.gov/assemblyarticles/210978PMC9151100/

Relevant links and references:

1. httphttps://www.cdccanada.govca/salmonellaen/heidelberg-02-13/
2. http://www.cdc.gov/salmonella/heidelberg-10-13/index.html
3. http://jcm.asm.org/content/41/9/4279.full
4. public-health/services/reports-publications/canada-communicable-disease-report-ccdr/monthly-issue/2005-31/restaurant-foodhandler-associated-outbreak-salmonella-heidelberg-gastroenteritis-identified-calls-local-telehealth-service-edmonton.html
5. https://webgate.ec.europa.eu/rasff-window/screen/notification/680242
6. https://webgate.ec.europa.eu/rasff-window/screen/notification/679279
7. https://webgate.ec.europa.eu/rasff-window/screen/notification/609282
8. https://archive.cdc.gov/www_cdc_gov/salmonella/heidelberg-01-14/advice-institutions.htmlhttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC3569330/