Molecular epidemiology and antimicrobial resistance of Vibrio parahaemolyticus isolates from the Pearl River Delta region, China

The Pearl River Delta (PRD) region in southern China is a densely populated area and a hotspot for Vibrio parahaemolyticus infections. However, systematic research on this pathogen, particularly comparing clinical and environmental strains, remains limited. This study analyzed the molecular epidemiology and antimicrobial resistance of 200 V. parahaemolyticus isolates from 12 cities in the PRD region from 2022 to 2023. The results indicated that the most prevalent serotypes were O3:K6 (39.5 %) and O10:K4 (27.5 %), predominantly found in clinical isolates. Most clinical isolates exhibited the characteristics of toxRS/new+, tdh + , and trh- , along with the sequence type 3 (ST3), while environmental isolates did not possess these genetic markers. Antimicrobial susceptibility testing showed that although clinically recommended antibiotics remain effective, some isolates have exhibited resistance, with environmental isolates displaying higher rates of antimicrobial resistance than clinical isolates. Moreover, a total of 26 antibiotic resistance genes (ARGs) associated with 10 antibiotic categories were identified, showing variations in distribution patterns among isolates from different sources. Phylogenetic analysis indicated that clinical isolates formed a distinct lineage, contrasting with the greater diversity observed in environmental isolates. Whole-genome analysis further revealed significant differences in pathogenicity- related genes between the two groups, with genes associated with biofilm formation and antimicrobial resistance being more commonly found in environmental isolates. These findings underscore the genetic variability and distinct patterns of antimicrobial resistance between clinical and environmental V. parahaemolyticus strains, highlighting the need for ongoing surveillance and targeted interventions to effectively address foodborne illnesses.