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The most common source of serovar Worthington is turkey, turkey ceca, and its production environment. This serovar has been reported in milk powder contamination, vegetables, and seafood. However, serovar Worthington has been frequently reported to cause infection especially in neonatal cases and the pediatric ward. Serovar Worthington tends to cause infection in vulnerable groups such as newborns or elderly. Although the symptoms caused by serovar Worthington infection are likely non-typhoidal infection symptoms such as diarrhea or vomiting, in some cases, it can develop to meningitis leading to fatality. In 1955, there was a report on serovar Worthington suspected causing gastroenteritis including vomiting from artificial feeding in several newborn babies in a small maternity ward at Indonesian hospital. The outbreak to newborn babies in the nursery of maternity ward also occurred in in hospital in Hong Kong in August 1974 leading to 1 from 13 cases died due to meningitis but the outbreak cause was unable to identified. However, the second outbreak occurred in five weeks after with infected five newborns and this time revealed that the outbreak caused by the contamination in tubing system of a suction apparatus which was used for baby's oropharyngeal suction. The outbreak causing by the same contamination also happened in Pakistan in early 1990s. Salmonella Worthington was recovered from 18 babies who received suction. Recently, serovar Worthington likely becomes multidrug-resistant bacteria challenging for treatment especially in neonates and elderly. 

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Genetic characteristics: Serovar Worthington has been found to be polyphyletic with 1 lineage and 1 stand-alone singleton. Salmonella Worthington isolates from preharvest turkey production sources pose both virulence and persistence by carrying virulence genes which are invA, aceK, and sopB together with resistance to many antibiotics (tetracycline, erythromycin, bacitracin, novobiocin, and rifampin). Salmonella Worthington has been reported on its ability either  either acquire third-generation cephalosporin resistance plasmid (bla_DHA-1-carrying IncFII plasmid) from Citrobacter amalonaticus or transfer its own resistance genes consisting of extended-spectrum cephalosporins, monobactam, and fluoroquinolone to Escherichia coli. Salmonella Worthington isolated from 

phylogenetic groups 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: Serovar Worthington has been commonly found in turkeys including their environments.

Geographical distribution: Serovar Worthington has been found in the United States, Indonesia, Hong Kong, India, Thailand, and Pakistan.

OutbreaksHuman outbreaks: Several human outbreaks have been associated with S. Sandiego, mostly associated with small pet turtles. There was a report on an outbreak of food poisoning with approximately 200 cases in California in 1938. Two isolates of Salmonella Sandiego were obtained from this outbreak Worthington. Below are some examples.

¹ Because of limitation of serological procedure at that time, this outbreak might be caused by pathogenic E. coli or Salmonella Worthington or both organisms

Border Rejections: One case of border rejections associated with serovar Worthington was reported.Border Rejections: Multiple border rejections associated with serovar Sandiego have been reported during August 2020 to December 2021 and they were all linked to black pepper imported from Brazil to Germany. Some border rejections were linked to multiple serotypes. 

¹ Salmonella Sandiego and Kedougou were found.

² Salmonella Sandiego, Poona, Newport, Kiambu, Freetown, and Rubislaw were found.  

³ Salmonella Sandiego and Abaetetuba were found.

Recalls: One recall linked to serovar Worthington has been reportedRecalls: There have been no recent recalls linked to this serovar.

¹ This recall was caused by  multistate human outbreak linked to Salmonella Sandiego and Salmonella enterica subspecies IIIb, linked to ready-to-eat Spring Pasta Salad from Hy-Vee brand grocery stores. a multistate outbreak.  Daniella brand mangoes grown in Mexico were recalled.

Relevant links and references:

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4. https://www.sciencedirect.com/science/article/pii/S0168160503003301?via%3Dihub#BIB20

5. https://www.foodsafetynews.com/2012/10/after-salmonella-outbreaks-growers-are-told-mangoes-are-high-risk-fruit/