Season-Specific Occurrence of Potentially Pathogenic Vibrio spp. on the Southern Coast of South Korea

Vibrio species are widely distributed in warm estuarine and coastal environments, and they can infect humans through the consumption of raw and mishandled contaminated seafood. In this study, we aimed to isolate and observe the distribution of enteropathogenicVibrio spp. from environments of the southern coast of South Korea over a season cycle. A total of 10,983 isolates ofVibrio spp. were obtained from tidal water and mud samples over a 1-year period from five sampling sites along the southwest coast of South Korea. We found thatVibrio alginolyticus (n = 6,262) andVibrio parahaemolyticus (n = 1,757) were ubiquitous in both tidal water and mud year round, whereasVibrio cholerae (n = 24) andVibrio vulnificus (n = 130) were seasonally specific to summer. While allV. cholerae isolates were nontoxigenic (non-O1 and non-O139), more than 88% ofV. vulnificus isolates possessed the virulence factor elastolytic protease (encoded byvvp ). Interestingly,V. parahaemolyticus , which was omnipresent in all seasons, contained the virulence factors thermostable direct hemolysin (encoded bytdh ) and thermostable direct hemolysin-related hemolysin (encoded bytrh ) in larger amounts in June (29trh -positive strains) and September (14tdh -, 36trh -, and 12tdh - andtrh -positive strains) than in December (4trh -positive strains) and February (3tdh -positive strains), and virulence factors were absent from isolates detected in April. To understand why virulence factors were detected only in the warm season and were absent in the cold season although the locations are static, long-term monitoring and particularly seasonal study are necessary.IMPORTANCE The presence of enteropathogenicVibrio species (Vibrio cholerae ,Vibrio parahaemolyticus , andVibrio vulnificus ), which cause acute diarrheal infection, septicemia, and wound infections upon ingestion through food and water, is usually associated with temperature. The World Health Organization (WHO) has estimated that there are 1.4 to 4.3 million cases and 28,000 to 142,000 deaths per year worldwide caused by cholera disease. In South Korea alone, consumption is as much as 52.4 kg of fish and shellfish per year per capita. Our findings suggested that seasonally specific acceleration of these possible pathogenicVibrio spp. may threaten seafood safety and increase the risk of illness in South Korea, where local people consume raw fish during warmer months.