Prevalence and distribution of non-typhoidal Salmonella enterica serogroups and serovars isolated from normally sterile sites: A global systematic review

Abstract

To inform coverage by potential vaccines, we aimed to systematically review evidence on the prevalence and distribution of non-typhoidal Salmonella enterica serogroups and serovars. We searched four databases from inception through 4 June 2021. Articles were included that reported at least one non-typhoidal S. enterica strain by serogroup or serovar isolated from a normally sterile site. Of serogrouped isolates, we pooled the prevalence of serogroup O:4, serogroup O:9, and other serogroups using random-effects meta-analyses. Of serotyped isolates, we pooled the prevalence of Salmonella Typhimurium (member of serogroup O:4), Salmonella Enteritidis (member of serogroup O:9), and other serovars. Of 82 studies yielding 24,253 serogrouped isolates, the pooled prevalence (95% CI) was 44.6% (36.2%-48.2%) for serogroup O:4, 45.5% (37.0%-49.1%) for serogroup O:9, and 9.9% (6.1%-13.3%) for other serogroups. Of serotyped isolates, the pooled prevalence (95%CI) was 36.8% (29.9%-44.0%) for Salmonella Typhimurium, 37.8% (33.2%-42.4%) for Salmonella Enteritidis, and 18.4% (11.4%-22.9%) for other serovars. Of global serogrouped non-typhoidal Salmonella isolates from normally sterile sites, serogroup O:4 and O:9 together accounted for 90%, and among serotyped isolates, serovars Typhimurium and Enteritidis together accounted for 75%. Vaccine development strategies covering serogroups O:4 and O:9, or serovars Typhimurium and Enteritidis, have the potential to prevent the majority of non-typhoidal Salmonella invasive disease.

Keywords: Salmonella vaccines; meta-analysis; non-typhoidal Salmonella; prevalence; systematic review.

Figure 1.

Proportion of non-typhoidal Salmonella enterica serogroups (A) and serovars (B) isolated from normally sterile sites, global, 1941–2019. Legend Figure 1: The error bars represent the 95%CI of the proportion. Legend Figure 1a: The complete list of serogroups is provided in Supplementary Table S5. Legend Figure 1b: The complete list of serovars is provided in Supplementary Table S6.

Figure 2.

Prevalence of non-typhoidal Salmonella enterica serovars from normally sterile sites ranked among top five, by UN region, 1941–2019 (79 articles, 23,971 isolates). Legend Figure 2: The error bars indicate 95%CI of the prevalence. *Others include other serovars that had rank sixth or higher. Data for Oceania is described in the Results section. The global map was downloaded from mapchart.net.

Figure 3.

Meta-analysis of prevalence of non-typhoidal Salmonella enterica from normally sterile sites for serogroup O:4, serogroup O:9, and other serogroups by UN region, 1941–2019 (82 articles, 24,253 isolates). Legend Figure 3: The error bars indicate 95%CI of pooled prevalence. Data for Oceania was not pooled and is described in the Results. Global map was downloaded from mapchart.net.