Salmonella Muenchen

Background: Salmonella enterica subsp. enterica serovar Muenchen (antigenic formula 6,8:d:1,2) is a serovar of the O:8 (C₂-C₃) serogroup. Serovar Muenchen was first described in 1932 and the first records of its isolation were documented in South and North America. Serovar Muenchen is one of the top 10 serovars responsible for human salmonellosis cases in US. CDC surveillance data indicated that serovar Muenchen represents approximately 2% of salmonellosis infections, ranking eighth among the leading Salmonella serovars. Since 2019, serovar Muenchen has been the most predominant serovar in Israel, identified in clinical, poultry, and food samples. It accounted for over 30% (937 of 3,112) of all clinical Salmonella isolates in 2019 and 39.5% (1,055 of 2,671) in 2020. This serovar was also the most common serovar in beef in Oceania. Between 2001 and 2007, serovar Muenchen ranked as the 15th most frequently isolated Salmonella serovar from humans across 37 countries participating in the WHO Global Foodborne Infections Network laboratory surveillance program.

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

Genetic characteristics: Serovar Muenchen has been found to be polyphyletic with four lineages identified. Cohen et al. revealed that the emergence of serovar Muenchen was characterized by a predominant clonal multidrug-resistant (MDR) strain carrying the epidemic megaplasmid pESI. This plasmid confers resistance to streptomycin/spectinomycin (aadA1), sulfonamides (sul1), tetracycline (tetRA), and trimethoprim (dfrA1), and demonstrates self-mobilization capability to E. coli and other Salmonella serovars. Notably, pESI also harbors multiple virulence determinants, including: (1) two chaperone-usher fimbrial clusters (Ipf and Klf); (2) a mercury resistance operon; and (3) the yersiniabactin iron acquisition system - all likely contributing to enhanced pathogenicity, host specificity, and environmental persistence. While initially reported in Israel, pESI-positive serovar Muenchen strains have now been identified in additional geographic regions such as South Africa, the UK, and US. Another Israeli study revealed that yersiniabactin gene cluster in pESI demonstrated specific upregulation under two key conditions: (1) mid-to-late logarithmic growth phase and (2) iron-depleted or oxidative stress (hydrogen peroxide) environments. Their findings revealed yersiniabactin's novel function in oxidative stress resistance and demonstrated its substantial contribution to serovar Infantis/Muenchen gut colonization in murine, promoting the worldwide transmission of pESI-bearing strains across diverse Salmonella lineages.

Animal reservoir: Swine, cattle, and poultry are reservoirs for serovar Muenchen. This serovar was also isolated from other animals such as raccoons and reptile. 

Geographical distribution: Serovar Muenchen has been found worldwide. 

Human outbreaks: Multiple human outbreaks have been linked to serovar Muenchen. Below are some examples. 

1 Twenty-six people infected with the outbreak strains of Salmonella Muenchen (25 people) or Salmonella Kentucky (1 person) were reported from 12 states.

Border rejections:

¹ Salmonella Saintpaul, Muenchen, Matadi, and Newport were found. 

² Salmonella Muenchen and Javiana were found.

³ Salmonella Muenchen and Rubislaw were found.

Recalls: 

¹ Sweetwater Farms LLC in Inman, KS, issued a recall of a single lot of its fresh alfalfa sprouts. This recall was resulted by a multistate outbreak described above. 

² A total of 14 different Salmonella serovars including Salmonella Anatum, Mbandaka, Senftenberg, Typhimurium, Agona, Muenchen, Irumu, Tennessee, Montevideo, Infantis, Muenster, Derby, O rough;d;e,n,x, and London were found. Kasel issued a recall of four lots of their products.  

³ Sun Orchard issued a recall of its unpasteurized orange juice products. This recall was resulted by a multistate outbreak described above. 

Relevant links:

1. https://stacks.cdc.gov/view/cdc/152398/cdc_152398_DS1.pdf
2. https://web.archive.org/web/20030315113355/http://www.cdc.gov/ncidod/dbmd/phlisdata/salmtab/2001/SalmonellaAnnualSummary2001.pdf
3. https://www.sciencedirect.com/science/article/pii/S1198743X22002889
4. https://journals.asm.org/doi/10.1128/aem.00591-19
5. https://www.liebertpub.com/doi/10.1089/fpd.2010.0787?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed
6. https://www.tandfonline.com/doi/10.1080/19490976.2024.2369339?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed#abstract
7. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2025.1547190/full#h10
8. https://boneandjoint.org.uk/Article/10.1302/0301-620X.46B4.697/pdf
9. https://www.aphis.usda.gov/sites/default/files/swine2006_is_salmonella_1.pdf
10. https://pmc.ncbi.nlm.nih.gov/articles/PMC4825103/
11. https://stacks.cdc.gov/view/cdc/22161
12. https://www.cdc.gov/salmonella/outbreaks/muenchen-03-25/investigation.html#:~:text=This%20means%20that%20people%20in,strain%2C%20also%20linked%20to%20geckos.
13. https://www.food.dtu.dk/english/newsarchive/2024/06/more-outbreaks-of-salmonella-in-2023
14. https://www.foodsafetynews.com/2021/12/salmonella-behind-a-quarter-of-eu-outbreaks-in-2020-with-20000-sickened/
15. https://archive.cdc.gov/#/details?url=https://www.cdc.gov/salmonella/muenchen-02-16/index.html
16. https://pubmed.ncbi.nlm.nih.gov/28494842/
17. https://outbreakdatabase.com/outbreaks/2003-outbreak-of-salmonella-muenchen-linked-to-cantaloupehoneydew-melon
18. https://www.sciencedirect.com/science/article/pii/S0362028X22009164?via%3Dihub
19. https://pmc.ncbi.nlm.nih.gov/articles/PMC88372/
20. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm4827a2.htm
21. https://www1.health.gov.au/internet/main/publishing.nsf/content/cda-cdi2109-pdf-cnt.htm/$FILE/cdi2109b.pdf
22. https://www.sciencedirect.com/science/article/pii/0195670182900652#:~:text=An%20outbreak%20of%20Salmonella%20muenchen%20infection%20involving%2028%20children%20and,occurred%20in%20two%20immunodeficient%20patients.
23. https://webgate.ec.europa.eu/rasff-window/screen/notification/654263
24. https://webgate.ec.europa.eu/rasff-window/screen/notification/461765
25. https://webgate.ec.europa.eu/rasff-window/screen/notification/442889
26. https://webgate.ec.europa.eu/rasff-window/screen/notification/432927
27. https://www.foodsafetynews.com/2016/02/123962/
28. https://www.foodsafetynews.com/2013/02/fda-flexes-muscles-to-achieve-kasel-pet-treat-recall/
29. https://marlerclark.com/news_events/sun-orchard-salmonella-outbreak-multistate