Epidemiological and genomic characterization of a rare foodborne outbreak caused by Bacillus paranthracis in Huzhou, China, 2024

Bacillus paranthracis belongs to Bacillus cereus group, Gram-positive and spore-forming bacteria, has the potential to induce foodborne diseases. However, globally reported outbreaks caused by B. paranthracis remain exceptionally rare and the genomic characteristics of outbreak isolates are seldom characterized. We applied epidemiological and genomic investigation to understand the cause of a foodborne outbreak in Huzhou, China, in 2024. Real-time fluorescent quantitative PCR was used for scanning the potential infectious agents, and 10 B. paranthracis isolates were identified, including 4 from patient samples and 6 from food samples. Epidemiological and genomics investigations showed that the B. paranthracis isolate of ST26 from uncooked rice was responsible for this outbreak. Genomic analysis indicated that the 8 strains of ST26 associated with the outbreak had high consistency in drug susceptibility phenotypes, antimicrobial resistance genes, virulence genes, and had very minimal genetic difference. This study underscores that need to implement systematic surveillance of B. paranthracis infections to safeguard public health.