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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  Serovar Napoli has been found to be monophyletic. An Italian study used genomic and phylogenetic approaches and found that an invasive strain of serovar Napoli was part of the Typhi subclade within clade A, with Paratyphi A as its closest serovar. This isolate was found to have the typhoid-associated genes hlyE and taiA (SPI-18), cdtB, pltA, and pltB  (CdtB-Islet), as well as the GICT18/1 islet. Another Italian study analyzed 112 serovar Napoli isolates and revealed that all tested isolates were susceptible to the examined antimicrobials, with SPI-associated genes (ssaQ, mgtC, spi_4D, and sopB) present in 75–100% of isolates, while avrA was rare (detected in only one human and four environmental isolates). The phage-related sopE1 appeared in 93% of strains, whereas sodC1 and gipA were limited to four and two environmental isolates, respectively. The fimbrial gene bcfC was universal in animal/food strains but less frequent in environmental (71.4%) and human (46.8%) isolates. Ten virulence profiles (VPs) were identified, with VP1–3 encompassing 99 of 112 isolates. PFGE analysis grouped 103 of 111 isolates into four major and three minor clusters (two isolates were unrelated), with dominant clusters strongly correlating with VP1–3.

Mastrorilli et al. further corroborated the genomic relatedness of serovar Napoli to typhoidal serovars (Salmonella Typhi and Paratyphi A), with two distinct subclades evident, including the biphyletically distributed ST-474. All sequence types (STs) were distributed across isolation sources and years. Compared to other non-typhoidal serovars, serovar Napoli harbors fewer SPIs and ARGs and rarely acquires plasmids. Notably, their study documented the second known instance of an extended-spectrum β-lactamase (ESBL)-producing serovar Napoli isolate and the first reported cases of MDR serovar Napoli isolates, all of human origin.

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. 

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