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Genetic characteristics: Chen et al. found that serovar Saintpaul appeared to be polyphyletic with four distinct phylogenetic groups identified. Within serovar Saintpaul, the comparative genomic analysis revealed 384 and 619 genes enriched in isolates from 5 human-associated (HA) and 4 non-human-associated (NHA) SNP clusters, respectively, that showed the strongest association with their isolation sources. This included five known HA-linked virulence genes located on Gifsy-1/Gifsy-2 prophages. Additionally, premature stop codons were more prevalent in 3 HA and 7 NHA genes. Cell culture experiments with representative strains from 4 HA and 3 NHA clusters found no increased invasion or intracellular survival capability in HA SNP clusters. However, the presence of sodCI (encoding a superoxide dismutase)—detected in 4 HA and 1 NHA clusters—correlated with enhanced survival in macrophage-like cells. In the study of worldwide population dynamics of serovar Saintpaul, Panzenhagen et al. found a total of 49 sequence types (STs), with ST-50 (787 genomes) and ST-27 (634 genomes) being the most common. All clinical isolates from South America, including PP_BR059 (isolated from a hospitalized patient in Ceará, Brazil), belonged to ST-50. Antimicrobial resistance (AMR) analysis indicated that 60% of Salmonella Saintpaul genomes had no resistance, while ST-27 contained the highest number of AMR strains. More specifically, among the 1,954 serovar Saintpaul isolates analyzed, 391 (20%) exhibited resistance genes associated with a multidrug-resistant phenotype. Additionally, seven isolates harbored the mcr-1 gene, while 17 isolates carried the CTX-M gene. They also identified separate evolutionary lineages within ST-50 and ST-27. PP_BR059 showed reduced macrophage invasion (3.82%) but notably higher survival rates inside cells at both 2 hours (68.72%) and 20 hours (25.68%) post-infection.

In Germany, a clonal line of Salmonella Saintpaul with a multidrug resistant phenotype was found in turkeys and human feces. These isolates exhibited resistance (either complete or intermediate) to ampicillin, amoxicillin-clavulanic acid, gentamicin, kanamycin, nalidixic acid, streptomycin, spectinomycin, and sulfamethoxazole, along with intermediate resistance or reduced susceptibility to ciprofloxacin and multiple third-generation cephalosporins (including ceftiofur and cefoxitin). Genotypic analysis revealed a conserved resistance pattern, featuring bla_TEM-1, aadB, aadA2, sul1, and a Ser83→Glu83 mutation in the gyrA gene. Additionally, all isolates carried a chromosomal class 1 integron harboring the aadB-aadA2 gene cassette. 

Animal reservoir: Unknown, but turkey and swine are likely to be reservoirs for serovar Saintpaul. 

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