ABSTRACT Nontyphoidal Salmonella enterica (NTS) infections in humans typically present as self-limiting gastroenteritis, but a small percentage progress to extraintestinal illness, including bacteremia. The spvRABCD ( S almonella p lasmid v irulence) locus is a plasmid-localized regulon and is hypothesized to contribute to NTS bacteremia. We analyzed 10,544 serotype Typhimurium (I 4,5,12:i:1,2) and 5,271 serotype I 4,5,12:i:- (abbreviated as “I 4:i:-”) genomes from human case isolates that were collected and uploaded to PulseNet between 1 January 2019 and 11 May 2022. We examined the relationships between isolate spv status, infection site, patient age, sex, and seven-gene multilocus sequence typing (MLST) sequence type. Comparing the spv + and spv− subpopulations of Typhimurium and I 4:i:- revealed respective 3.5- and 2.2-fold increases in the proportion of blood isolates among the spv + subpopulation. Bivariate analysis revealed associations between spv + status, patient age group, patient sex, and infection site for both serotypes. Generalized estimating equation models found increased odds of isolation of spv + isolates from blood compared with stool for both serotypes (Typhimurium adjusted odds ratio aOR: 4.1 95% CI: 3.4–5.1 P < 0.001; I 4:i:- aOR: 2.3 95% CI: 1.6–3.2 P < 0.001) and increased odds of urine vs stool isolation for spv + isolates for Typhimurium (aOR: 1.6 95% CI: 1.3–2.0 P < 0.001). Patient age and sex were also predictive of blood and urine isolation, relative to stool. Additionally, MLST sequence types with higher rates of spv carriage showed higher rates of blood infections. In summary, our analysis strongly supports a role for the spv locus in bloodstream infection cases caused by Typhimurium and I 4:i:-. IMPORTANCE This study details a comprehensive analysis of 15,815 clinical isolates of Salmonella Typhimurium and I 4,5,12:i:- collected through the PulseNet USA Network to investigate the role of the spvRABCD locus in nontyphoidal Salmonella infections, with a focus on its association with bloodstream infections. These findings demonstrate increased odds of bacteremia in strains that carry the spv genes in two prevalent nontyphoidal serotypes. This research builds on and confirms previous studies’ implications that these genes contribute to the risk of blood infections by utilizing large human data sets to directly connect bacterial genotype to a specific isolation site in a human. This work both enhances our understanding of the virulence mechanisms of Salmonella and underscores the importance of genomic surveillance in identifying strains that pose a heightened risk for invasive disease.
Tierney et al. (Mon,) studied this question.