Ann Lab Med.  2025 May;45(3):312-321. 10.3343/alm.2024.0378.

Epidemiology of Nontyphoidal Salmonella Infections in Korean Children and Genetic Factors Associated with Extra-intestinal Invasion: A Whole-genome Sequencing Analysis

• Kang HM
• Chu J
• Yoo IH
• Yoo IY
• Shin JI
• Seo MR
• Chung YJ
• Jung SH
• Park YJ

• KMID: 2567973
• DOI: http://doi.org/10.3343/alm.2024.0378

Abstract

Background
Understanding the virulence and pathogenicity of invasive nontyphoidal Salmonella (iNTS) in children may support timely treatment and enable closer monitoring of chronic infections. iNTS epidemiology in Asia remains inadequately described. We analyzed the genetic diversity and virulence genes associated with extra-intestinal invasion in Korean children.
Methods
Salmonella isolates from children < 18 yrs of age diagnosed with moderate-tosevere salmonellosis between January 2019 and December 2021 were subjected to antibiotic susceptibility testing and whole-genome sequencing.
Results
In total, 58 cases were included. We identified 20 serotypes, the most prevalent being Salmonella Enteritidis (N = 21), followed by Infantis (N = 6), I 4,[5],12:i:- (N = 5), and Bareilly (N = 5). Extra-intestinal invasion occurred in 12 (20.7%) cases involving Salmonella Oranienburg (2/2), Give (1/1), Javiana (1/1), Paratyphi B var. L(+) tartrate+ (1/1), Schwarzengrund (1/1), Singapore (1/1), Montevideo (1/2), Saintpaul (1/2), I 4:b:- (1/2), Infantis (1/6), and Enteritidis (1/21). While the numbers of total virulence genes and genes belonging to major virulence categories did not significantly differ between iNTS and noniNTS, several genetic factors, including Salmonella pathogenicity island (SPI)-1 (P = 0.039), SPI-2 (P = 0.020), SPI-5 (P = 0.014), SPI-13 (P = 0.010), cytolethal distending toxin-related genes (P = 1.4 × 10 ^–4 ), fepC (P = 0.021), and tcpC (P = 0.040) were more frequent in invasive isolates.
Conclusions
Salmonella Enteritidis-ST11 predominated in infections among Korean children, but invasive isolates were rare. Early detection of genetic factors associated with extra-intestinal invasion will be helpful for prompt and appropriate treatment.

Keyword

Extra-intestinal invasion; Genetic factor; Nontyphoidal Salmonella; Salmonella pathogenicity island; Whole-genome sequencing

Figure

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  Fig. 1 Distribution of serotypes and sequence types among children with salmonellosis in Korea.

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  Fig. 2 Virulence profile and distribution. (A) Heatmap of 175 virulence genes present in 58 Salmonella isolates. The X-axis and Y-axis represent virulence categories and serotypes, respectively. (B) Number of virulence genes by serotype. Red dots represent extra-intestinal invasive isolates. The mean and 95% confidence interval are represented with black lines.

• 

  Fig. 3 Phenotypic and genotypic profiles of 58 nontyphoidal Salmonella isolates collected in South Korea between January 2019 and December 2021. Major sequence types and serotypes are represented by distinct colors, whereas other serotypes/sequence types are uniformly displayed in gray. Phenotypic resistance is marked with a black square for all drugs except ciprofloxacin. Phenotypic intermediate resistance to ciprofloxacin is marked with a black square.

Reference

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