S. Muenchen¶

At a Glance


Antigenic Formula	`6,8:d:1,2`
Serogroup	O:8 (C2-C3)
NCBI Pathogen Detection	View isolates

Background Information¶

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.

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/Animal Outbreaks¶

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

Year	Location	Associated source	Number of cases
2024-2025	US: multistate	Geckos	14
2023	Denmark	Unknown	31
2020	Germany	Coconut pieces or flakes	161
2016	US: multistate	Alfalfa sprouts	26¹
2014	Germany	Raw pork sausage	247
2013	Germany	Raw pork	203
2003	US: multistate	Cantaloupe, honeydew melon	58
2001	Germany	Pork	198
1999	US: multistate	Alfalfa sprouts	At least 157
1999	US: multistate, Canada	Orange juice	298
1997	Australia	Corn beef	24
1980	London	Nosocomial in pediatric hospital	30

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¶

Year	Exporting country	Importing country	Associated source	Product category
2023	South Africa	Germany	Dog chews (ostrich meat)	Pet food
2021	Brazil	Germany	Black pepper¹	Herbs and spices
2020	Brazil	Germany	Black pepper²	Herbs and spices
2020	Brazil	Germany	Black pepper³	Herbs and spices

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

² Salmonella Muenchen and Javiana were found.

³ Salmonella Muenchen and Rubislaw were found.

Recalls¶

Year	Location	Recalled food	Type
2016	US: multistate	Alfalfa sprouts¹	Fruits and vegetables
2013	US: CO	Beef bully sticks²	Pet food
1999	US: multistate	Unpasteurized orange juice³	Non-alcoholic beverages

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.