Prevalence and virulence of Vibrio parahaemolyticus isolated from clinical and environmental samples in Huzhou, China.

BACKGROUND: Vibrio parahaemolyticus has emerged as the leading cause of seafood-associated infections worldwide. Previous studies have shown that V. parahaemolyticus can be detected in both environmental and clinical samples. However, the molecular characteristics of V. parahaemolyticus isolated from these sources remain unknown. RESULTS: This study examined 128 strains of V. parahaemolyticus isolated from clinical and environmental samples collected between 2020 and 2023 in Huzhou, China. We identified 73 serotypes; O10:K4, O3:K6, and O4:KUT were the dominant serotypes among clinical isolates. We examined the proliferation and motility of major epidemic strains from environmental and clinical samples. Genetic diversity and evolution were assessed by average nucleotide identity (ANI), phylogenetic tree construction, and multilocus sequence typing (MLST). Furthermore, we identified 13 novel sequence types (STs) among the environmental isolates, indicating that V. parahaemolyticus strains are widely distributed and evolve rapidly in the environment in Huzhou, China. We found 206 virulence genes among these isolates, indicating that environmental isolates possess numerous virulence genes. Additionally, we detected 4 strains carrying the tdh or trh gene, which may increase their pathogenicity. The prediction results of antibiotic resistance genes shown that environmental isolates may carry up to 104 resistance genes, compared to 30 in clinical isolates. CONCLUSIONS: We observed that the environmental serotypes of V. parahaemolyticus exhibit greater diversity compared to clinical isolates, which are predominantly concentrated in three major serotypes. Furthermore, a considerable genetic distance was found between most clinical and environmental isolates. Notably, some clinical isolates show a closer genetic proximity to environmental isolates. Additionally, the distribution of virulence genes, specifically T3SS and tdh, significantly differs among isolates from these two distinct sources. The prediction results for antibiotic resistance genes suggest that environmental isolates may harbor a broader spectrum of resistance genes. The findings of this study provide new insights into the phylogenetic relationships between V. parahaemolyticus strains from clinical and environmental sources, and they enhance the MLST database.