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

BACKGROUND

Understanding the virulence and pathogenicity of invasive nontyphoidal (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-to-severe 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 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 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 non-iNTS, several genetic factors, including pathogenicity island (SPI)-1 ( =0.039), SPI-2 ( =0.020), SPI-5 ( =0.014), SPI-13 ( =0.010), cytolethal distending toxin-related genes ( =1.4×10), ( =0.021), and ( =0.040) were more frequent in invasive isolates.

CONCLUSIONS

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.