A foodborne outbreak of Salmonella Paratyphi C in a Chinese middle school: Genomic tracing and epidemiological characterization

Background

Salmonella Paratyphi C is an infrequent etiological agent of enteric fever, with sporadic cases primarily reported in Asia and Africa. Documented outbreaks remain exceedingly rare, and epidemiological data on such events are notably scarce.

Methods

This study investigated a paratyphoid fever outbreak caused by S. Paratyphi C at a secondary school in China in 2023. Comprehensive field epidemiological investigations were conducted, including environmental sampling and the collection of clinical specimens. All outbreak-associated isolates underwent antimicrobial susceptibility testing, whole-genome sequencing, and in-depth bioinformatics analysis. Single-nucleotide polymorphism profiling and core genome multilocus sequence typing were employed to elucidate the genetic relatedness of the isolates.

Results

A total of 11 S. Paratyphi C strains, characterized by the antigenic formula 6,7:c:1,5, were recovered from a variety of sample sources. Genomic analyses revealed striking homogeneity across all isolates, with uniform multilocus sequence types, identical antimicrobial resistance patterns, and shared virulence-associated genes. Phylogenetic reconstruction demonstrated a tightly clustered lineage, corroborated by highly similar circular genome structures, suggesting a common source of infection.

Conclusions

This investigation offered critical insights into a rare foodborne outbreak caused by S. Paratyphi C, bridging significant knowledge gaps regarding its epidemiology and genetic characteristics. The findings underscored the global diversity and potential public health threat of S. Paratyphi C, reinforcing the urgent need to enhance food safety monitoring and improve outbreak preparedness strategies both in China and internationally.