Background: Salmonella enterica subsp. enterica serovar Napoli (antigenic formula 1,9,12:l,z₁₃:e,n,x) is a serovar of the O:9 (D₁) serogroup. In 2006, serovar Napoli ranked 22nd in the Enter-net Salmonella database, accounting for 295 cases (0.28%) out of 105,635 reported across 29 European countries. Between 2000 and 2006, Europe saw a 140% rise in serovar Napoli infections, with over 87% of cases originating in France, Italy, and Switzerland. This serovar has been an emerging serovar in these three countries, particularly in Italy, where it is the fourth most frequent Salmonella serovar, responsible for 2-4% of human infections. Additionally, from 2010 to 2014, serovar Napoli was the leading cause of invasive salmonellosis, affecting 40 out of 687 cases in Italy—a notably higher invasive rate compared to other nontyphoidal serotypes. 

It was isolated from rucola and wild bird samples collected in Italy between 2004 and 2014 (Fisher et al., 2009; Mancini et al., 2014; Gori et al., 2018).  Although it is a nontyphodial Salmonella strain some if its symptoms, including a prolonged incubation period (7–14 days), high fever, bacteremia, and elevated rates of hospitalizations, are similar to those caused by typhoidal Salmonella. 

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

Genetic characteristics: Serovar Napoli has the typhoid-associated genes hlyE and taiA (SPI-18), cdtB, pltA, and pltB (CdtB-Islet), as well as the GICT18/1 islet.

Animal reservoir: Unknown, poultry and wild boars may be potential reservoirs for serovar Napoli. It was also isolated from wild birds but uncommonly from cattle. 

Geographical distribution: Serovar Napoli has been reported in US, Canada, Australia, and Europe, mainly in Italy. 

Human outbreaks:

Animal outbreaks:

¹ The herd consisted of 310 cows. There were four animals infected: two calves and two milking cows.

Border rejections: There have been no recent border rejections linked to this serovar. 

Recalls: There have been no recent recalls linked to this serovar. 

Relevant links:

1. https://pubmed.ncbi.nlm.nih.gov/19534593/
2. https://www.escaide.eu/sites/default/files/documents/ESCAIDE-2012-abstract-book.pdf
3. https://www.scielosp.org/article/aiss/2014.v50n1/96-98/
4. https://www.liebertpub.com/doi/abs/10.1089/fpd.2016.2206

1. https://pmc.ncbi.nlm.nih.gov/articles/PMC8276318/#:~:text=So%20far%2C%20it%20has%20been,undoubted%20benefit%20at%20community%20level.
2. https://link.springer.com/article/10.1007/s10393-023-01625-y
3. https://efsa.onlinelibrary.wiley.com/doi/pdf/10.2903/sp.efsa.2022.EN-7687
4. https://www.foodsafetynews.com/2023/12/salmonella-outbreak-over-in-norway-but-source-not-found/
5. https://www.liebertpub.com/doi/full/10.1089/fpd.2015.2091
6. https://pubmed.ncbi.nlm.nih.gov/6131266/
7. https://pmc.ncbi.nlm.nih.gov/articles/PMC11718894/