Salmonella Muenster

Background: Salmonella enterica subsp. enterica serovar Muenster (antigenic formula 3,{10}{15}{15,34}:e,h:1,5) is a serovar of the O:3,10 (E₁) serogroup. The serovars previously known as Newhaw and Arkansas are now classified as variants of serovar Muenster. Newhaw is designated as Muenster var. 15⁺ (converted by phage ε15), while Arkansas is Muenster var. 15⁺,34⁺ (converted by phages ε15 and ε34). These variants occupy the same serological position as group O:4 (B) strains, which express factor 1 upon conversion but had not been assigned new names. During 1986, Salmonella spp. (primarily serovar Muenster) was detected in 2.9% of raw milk samples from dairy herds in southwestern Ontario, but the prevalence declined to zero within approximately a year. According to the 1996 USDA prevalence study, serovar Muenster ranked as the seventh most frequent serotype, representing 4.7% of all Salmonella spp. isolates in US dairy operations. Serovar Muenster can cause abortion or diarrhea in cows in late gestation.

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

Genetic characteristics: Serovar Muenster has been found to be polyphyletic with two lineages identified and two stand-alone singletons that do not cluster with any other Salmonella Muenster isolates. Chang et al. found an Muenster isolate with a 260-kb bla _CTX-M-55-qnrS1-bearing IncHI2 plasmid. Argentinian researchers reported that serovar Muenster had low pathogenic potential in swine. Osman et al. revealed that 2 out of 5 Muenster isolates included in their study exhibited resistance to lincomycin, streptomycin and chloramphenicol. Nguyen et al. collected a total of 47 duck carcass samples in wet markets during October 2019 in Vietnam and isolated seven strains of serovar Muenster belonging to ST 321. Among these seven isolates, three of them harbored C63PI, an iron transport system located in SPI-1. Three plasmid replicons were identified in these Muenster isolates (IncHI2_1, IncHI2A_1, and IncL/M(pMU407)_1_pMU407). All seven isolates exhibited ESBL phenotypes and carried the bla_CTX-M-55 variants (i.e., bla_TEM-1B, bla_CTX-M-55, bla_TEM-206, bla_TEM-214, and bla_TEM-141).

Animal reservoir: Dairy cattle is the reservoir for serovar Muenster. This serovar was also isolated from other animals such as pet bearded dragons, and birds (Tympanuchus cupido, Antigone canadensis).

Geographical distribution: According to the metadata from NCBI PD, serovar Muenster has been reported globally but primarily in US. Among a total of 2,659 serovar Muenster isolates available in NCBI PD (accessed 04/29/2025), there were 2,040 isolates collected in US.

Human outbreaks:

Year	Location	Associated source	Number of cases
2020	US: multistate	Pet bearded dragons	18
2008	France	Goat's cheese	25
2016	US: multistate	Live poultry	25
1980	Saudi Arabia	Roast beef	12

Border rejections:

Year	Exporting country	Importing country	Associated source	Product category
2024	Nigeria	Italy	Sesame seeds	Nuts, nut products and seeds
2020	Brazil	Germany	Black pepper	Herbs and spices
2020	Poland	Bulgaria	Frozen chicken leg quarters¹	Poultry meat and poultry meat products

¹Salmonella Infantis and Muenster were found.

Recalls:

Year	Location	Associated source	Type
2024	Germany, Ireland	Tahini from Lebanon	Nuts, nut products and seeds

Relevant links:

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Salmonella Muenster