Salmonella Tennessee

Background: Salmonella enterica subsp. enterica serovar Tennessee (antigenic formula 6,7,14:z₂₉:[1,2,7]) is a serovar of the O:7 (C₁) serogroup. Infections from this serotype are uncommon, representing approximately 0.1% of US Salmonellosis cases between 1994 and 2004 and averaging just 52 per year. At the beginning of 1994 and in the following months, Denmark observed a substantial increase in serovar Tennessee cases among broiler flocks. Unlike typical Salmonella infections limited to the gut, certain serotypes, including serovar Tennessee, show a greater tendency to invade the urinary tract. Notably, urine isolates of serovar Tennessee surged from 15% (1995–2004) to 27% during 2005–2006 in US.

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

Genetic characteristics: Serovar Tennessee has been found to be polyphyletic with two lineages identified. Wilson et al. analyzed 71 serovar Tennessee isolates and identified four clades with a total of 114 SNPs. Additionally, a 110 kb phage was identified, showing similarity to Salmonella phage SSU5 (103,299 bp). A transcriptomic study conducted by Li et al. found that after two hours of air-drying at 11% relative humidity, around 25% of the open reading frames (ORFs) in the serovar Tennessee genome and 20% in serovar Typhimurium LT2 showed differential expression (more than 2-fold change). Among the most significantly affected functional groups (greater than 5-fold change) in both strains, fatty acid metabolism had the highest expression shift, accounting for 51% of the total expression change in serovar Tennessee and 35% in LT2. Compared to LT2, serovar Tennessee exhibited stronger expression changes in stress response and cell envelope modification genes but weaker changes in protein biosynthesis. Flagella gene expression was more suppressed in serovar Tennessee’s stationary-phase cells than in LT2, both before and after drying. Additionally, desiccation triggered a notable increase in the osmolyte trehalose in serovar Tennessee, whereas no detectable rise occurred in LT2—a finding that aligns with the expression trends of trehalose-related biosynthesis and degradation pathways in both strains.

Animal reservoir: Unknown, but chicken may be the potential reservoir for serovar Tennessee. This serovar was also isolated from other animals such as snake, seagull, and turtle.

Geographical distribution: According to the metadata from NCBI PD (accessed on 05/21/2025), serovar Tennessee has been reported occasionally worldwide but is found mainly in US and UK, with 660 and 167 out of a total of 1,174 serovar Tennessee isolates from those regions.

Human outbreaks:

Year	Location	Associated source	Number of cases
2008	Germany	Bearded dragons	18
2006-2007	US: multistate	Peanut butter	715
2006	US: CO	Not identified¹	10
1992-1993	Canada and US	Milk products and infant formula	48

¹ The outbreak occurred in a neonatal intensive care unit.

Border rejections:

Year	Exporting country	Importing country	Associated source	Product category
2020	Russia	Finland	Rape seed meal	Feed materials
2020	China	Germany	Organic soy bean cake	Feed materials

Recalls:

Year	Location	Associated source	Type
2023	Romania	Fish flour from Latvia	Feed materials
2021	Germany, Czech Republic	Sesame paste from Syria	Nuts, nut products and seeds

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Salmonella Tennessee