Genetic Analysis of Clinical and Environmental Vibrio vulnificus Isolates from Jeollanam-do, South Korea

Vibrio vulnificus is an opportunistic human pathogen with a mortality rate exceeding 50%.Human infection can occur through the consumption of raw seafood or the exposure of open wounds to contaminated water.This study aims to characterize the epidemic and virulence potentials of V. vulnificus isolates from clinical and environmental samples.We collected 35 clinical isolates between 2014 and 2022 and 42 environmental isolates between 2020 and 2022 from Jeollanam-do, South Korea.Genotyping was conducted using PCR targeting the 16S rRNA gene (rrn) and virulence-correlated gene (vcg).Multi-locus sequence typing (MLST) was performed by amplifying internal fragments of 10 house-keeping genes and concatenated sequences of 10 genes were used for phylogenetic analysis.The majority of both clinical (80%) and environmental (81%) isolates were of the C-genotype (rrnB/vcgC).MLST analysis revealed high clonal diversity, with 59 distinct sequence types (STs) identified among 77 isolates.The most prevalent ST, ST629 (n=10), was found exclusively in environmental isolates collected at low temperature (3.7~16.6).Phylogenetic analysis identified two arbitrarily lineages, with most isolates (70 of 77) belonging to lineage C. Clinical and environmental isolates from the warm season were dispersed across both lineages, whereas all isolates from the cold season belonged to lineage C. Given the high genetic diversity across isolate sources and genotypes, MLST-based phylogenetic analysis is challenging for predicting the pathogenic potential of V. vulnificus.This highlights the need for new genetic markers with epidemiological relevance to identify high-risk strains for public health and environmental risk management.