Salmonella Montevideo

Background: Salmonella enterica subsp. enterica serovar Montevideo (antigenic formula 6,7,14:g,m,[p],s:[1,2,7]) is a serovar of the O:7 (C₁) serogroup.

S. Montevideo is the sixth most common serovar isolated from humans and animals in the U.S. Outbreaks caused by S. Montevideo have been associated with imported spices and live poultry. Whole genome sequencing of a number of S. Montevideo strains have been conducted, including an study that identified one strain with two large plasmids that encoded antimicrobial and heavy metal resistance genes.  It has been reported, among the most common serovars, in the U.S., Europe, Latin America, Asia, and Oceania

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

Genetic characteristics: Serovar Montevideo was found to be polyphyletic with four clades identified. Within the largest clade, Montevideo A, the subclade Montevideo A-10 was cattle-associated, whereas Montevideo A-7 was associated with environmental sources (e.g., water, sediment). The cattle-associated Montevideo-A-10 lineage (emerged ~1905) contained two clonal subclades, Montevideo-A-10-I (29% of isolates, emerged ~1968) and Montevideo-A-10-II (13% of isolates, emerged ~1958), both showing increased cattle-associated prevalence over time. Lalsiamthara and Lee used serovar Montevideo and Typhimurium to infect chickens and rabbits. They revealed that infected birds showed no visible signs of illness, and histopathology revealed only mild damage to intestinal epithelium and splenic parenchyma despite consistent serovar Montevideo isolation from these tissues. Salmonella Montevideo was internalized by chicken peritoneal macrophages at rates comparable to Salmonella Typhimurium but demonstrated greater susceptibility to chicken serum complement than rabbit serum. In mock-infected layers, serovar Montevideo caused transient internal egg contamination at trace levels, persisting for one week post-inoculation, suggesting infection of Salmonella Montevideo in chickens is asymptomatic and sub-clinical.

Animal reservoir: Cattle and chicken are the reservoirs for serovar Montevideo. 

Geographical distribution: Serovar Montevideo is globally distributed. 

Outbreaks: Numerous outbreaks in different countries have been linked to serovar Montevideo, nuts have been associated with several of these outbreaks. Below are some examples. 

¹ There were a total of 11 people infected with the outbreak strains of Salmonella Montevideo (9 cases) and Senftenberg (2 cases) reported from nine states.

² Salmonella Montevideo (4 cases) and Mbandaka (12 cases) infections were reported from nine states.

³ Eleven people were infected by Salmonella Senftenberg. These 11 cases were not included in the overall case count (272). 

Border rejections: Multiple border rejections associated with serovar Montevideo have been reported. Below are some examples.

¹ Salmonella Anatum, Brancaster and Montevideo were found.

² Salmonella Abony and Montevideo were found.

³ Salmonella Bredeney and Montevideo were found. 

Recalls: Multiple recalls associated with serovar Montevideo have been reported. Below are some examples.

¹ Wonderful Pistachios of Lost Hills, California issued a voluntary recalled. The recalled pistachios, distributed under the Wonderful, Paramount Farms, and Trader Joe’s brands, were sold across the US as well as in Canada, Mexico, and Peru.

Relevant links:

1. https://journals.asm.org/doi/10.1128/mbio.01913-24
2. https://www.nature.com/articles/srep46232
3. https://pubmed.ncbi.nlm.nih.gov/23566273/
4. https://www.nature.com/articles/srep46232#:~:text=Abstract,poultry%20or%20poultry%20meat%20products.
5. http://www.jbjc.org/en/article/doi/10.3784/j.issn.1003-9961.2014.12.022
6. https://www.sciencedirect.com/science/article/pii/S0362028X23068151
7. https://archive.cdc.gov/#/details?url=https://www.cdc.gov/salmonella/montevideo-01-18/index.html
8. https://archive.cdc.gov/www_cdc_gov/salmonella/montevideo-03-16/index.html
9. https://archive.cdc.gov/#/details?url=https://www.cdc.gov/salmonella/montevideo-tahini-05-13/index.html
10. https://archive.cdc.gov/#/details?url=https://www.cdc.gov/salmonella/montevideo-06-12/index.html
11. https://www.eurosurveillance.org/content/10.2807/ese.16.50.20040-en
12. https://pmc.ncbi.nlm.nih.gov/articles/PMC2870340/
13. https://pubmed.ncbi.nlm.nih.gov/12501260/
14. https://pubmed.ncbi.nlm.nih.gov/10491878/
15. https://webgate.ec.europa.eu/rasff-window/screen/notification/723009
16. https://webgate.ec.europa.eu/rasff-window/screen/notification/702610
17. https://webgate.ec.europa.eu/rasff-window/screen/notification/685839
18. https://webgate.ec.europa.eu/rasff-window/screen/notification/473167
19. https://webgate.ec.europa.eu/rasff-window/screen/notification/726067
20. https://webgate.ec.europa.eu/rasff-window/screen/notification/657396
21. https://webgate.ec.europa.eu/rasff-window/screen/notification/607162
22. https://webgate.ec.europa.eu/rasff-window/screen/notification/603115