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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. This serovar was first isolated in Uruguay in 1936 from an infant with chronic enterocolitis.

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. 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.

Nguyen et al. also identified four clades for serovar Montevideo in their study. They found that clade I strains have up to two large integrated mobile genetic elements (MGEs), each approximately 30–60 kb in size. A phage attachment site, known to be targeted by the lambdoid prophage Gifsy-2—a factor linked to virulence in Salmonella Typhimurium LT2 (which inserts between pepN and pcnB)—was found to be occupied by different prophages in Montevideo clades I and III (SM F7-F9). A prophage similar to Gifsy-1, Gifsy-2, or SEN34 (SM F8-F9), carrying the virulence genes gtgE and msgA but missing sodCI, was detected in all clade III strains except ATCC BAA710. Additionally, all clade IV strains contained Fels-2-like and Salmon_vB_SosS_Oslo-like prophages (SM F5 and SM F6, respectively), though these were not exclusive to clade IV. Furthermore, Montevideo isolates from all four clades were found to carry Salmonella pathogenicity islands (SPIs) with similarities to SPI-1 through SPI-6.

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

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