Whole-genome sequencing of Listeria monocytogenes isolated from retail enoki mushrooms in China highlights public health risk

The food-borne pathogen Listeria monocytogenes (L. monocytogenes, Lm) has been identified as the cause of listeriosis. In recent years, several outbreaks in Europe and the U.S. have been traced to contaminated enoki mushrooms. However, the genomic characterization of Lm from enoki mushrooms in China has not been well elucidated. In this study, 144 strains of L. monocytogenes from retail enoki mushrooms across 24 provinces of China in 2021 were characterized based on whole genome sequencing. All the isolates were classified into two lineages: lineages I (n = 54) and lineages II (n = 90) with the four most predominant clonal complexes CCs (CC8, CC87, CC14, and CC5) which are closely consistent with the ST distribution observed in Chinese clinical strains. According to WHO/FAO classification based on the LIPI-1 to 4 and inlA gene, 81.9 % were classified as hypervirulent or virulent strains. Core genome SNP analysis revealed close genetic relationships between enoki mushroom isolates and Chinese clinical strains, especially for CC8/ST8, CC87/ST87, and CC14/ST91, suggesting potential foodborne transmission. Additionally, 56.3 % harbored the SSI-1 stress survival islet, indicating adaptation to food processing environments. These findings highlight enoki mushrooms as possible reservoirs for transmitting pathogenic Lm strains to humans, emphasizing the need for strengthened surveillance and control.