Comparison of bioaccumulation and elimination of Escherichia coli and male-specific bacteriophages by ascidians and bivalves

Trend of Pathogenic Vibrio parahaemolyticus Occurrences in Bivalve Molluscs Harvested in Sardinian Coastal Environments Between 2011 and 2018

The aim of the present study was to evaluate Vibrio parahaemolyticus occurrences in bivalve molluscs harvested from Sardinian coastal environments between 2013 and 2015. The prevalence of pathogenic V. parahaemolyticus isolates is based on the detection of the two major virulence genes thermostable direct hemolysin (tdh) and thermolabile hemolysin (trh) To assess changes between 2011 and 2018 in the prevalence of V. parahaemolyticus in bivalve molluscs, we compared our results with those of previous investigations. In total, 2,933 samples were collected: 1,079 in 2013, 1,288 in 2014, and 566 in 2015. The mean prevalence of V. parahaemolyticus in shellfish was 3.5% in 2013, 1.7% in 2014, and 3.5% in 2015. The highest percentage of positive samples in 2013 and 2014 was observed in clams (3.5% and 2.7%, respectively), whereas in 2015, it was reported in oysters (15.1%). By comparing the sampling period of 2011-2014 with that of 2015-2018, an increase in the prevalence of V. parahaemolyticus was observed in shellfish (p < 0.05). In parallel, 208 potentially enteropathogenic V. parahaemolyticus strains were identified through the years 2011-2018 and, in particular, 10 trh+ and six tdh+ isolates. Our present study provides information regarding trends of V. parahaemolyticus occurrences in bivalve molluscs harvested from Sardinian coastal environments between 2011 and 2018 suggesting that the prevalence varies depending on the sampling period and shellfish species.

Level of contamination in the feces of several species at major inland pollution sources in the drainage basin of Yeoja Bay, Republic of Korea

We assessed the levels of fecal contamination and the originating species of 12 major inland pollutants in the drainage basin of Yeoja Bay. The presence of the human-specific (HF183), ruminant-specific (BacR and Rum-2-Bac), pig-specific (Pig-Bac-2 and Pig-2-Bac), avian-specific (GFD), and gull-specific (Gull2) markers in water samples (n = 34) from 12 inland pollution sources around Yeoja Bay was analyzed. HF183 was detected in 97% of the water samples, and all major inland pollution sources were contaminated with human feces. BacR and Rum-2-Bac were detected in 94% and 11%, respectively, of the water samples. Pig-2-Bac was not detected in the inland pollution sources, but site L5 might be contaminated with swine feces. Gull2 was not detected, whereas GFD was detected in 26% of the water samples. This study highlights the utility of a MST toolbox approach for characterizing the water quality of inland pollution sources and identifying the feces producing species.

Occurrence, virulence, and antimicrobial resistance of Vibrio parahaemolyticus isolated from bivalve shellfish farms along the southern coast of Korea

Vibrio parahaemolyticus is the most common pathogen causing seafood-borne illnesses in Korea. The present study evaluated the occurrence, virulence, and antimicrobial resistance of V. parahaemolyticus in seawater and bivalves obtained in 2016 from the southern coast of Korea, an important region for commercial aquaculture industries, especially the Korean raw seafood culture. V. parahaemolyticus was detected in 87 of 160 (54.4%) bivalve samples and in 32 of 130 (24.5%) seawater samples. Especially high levels were detected during summer to early autumn. All the seawater and bivalves contained less than 2 and 5% of the tdh and trh genes of the isolates, respectively, and seawater isolates possessed two fewer genes than the bivalve isolates. Of 23 antimicrobials tested, three agents (ofloxacin, norfloxacin, and trimethoprim/sulfamethoxazole) effectively treated V. parahaemolyticus illness due to the sensitivity of the isolates. The isolates were highly resistant to ampicillin, however, excluding it as a treatment option. More than half of the isolates exhibited resistance to at least three antimicrobials. These findings indicate the importance of an integrated monitoring and surveillance program noting the occurrence, virulence, and antimicrobial resistance patterns of V. parahaemolyticus in various aquatic sources for preventing human health risks from seafood consumption.

Occurrence and virulence of Vibrio parahaemolyticus isolated from seawater and bivalve shellfish of the Gyeongnam coast, Korea, in 2004-2016

We determined the abundance and virulence of Vibrio parahaemolyticus in seawater and bivalves from the Gyeongnam coast in Korea, a major area for the seafood industry, during 2004-2016. V. parahaemolyticus is one of the most common pathogen causing seafood-borne illnesses in Korea, and increases during the summer. Its occurrence in seawater and bivalve samples was seasonally dependent, with high levels during the summer to early autumn. There were more strains in the area of sea continually exposed to inland wastewater. Only 5.1% and 3.5% of V. parahaemolyticus isolates from seawater and bivalves, respectively, had the trh gene, and only the bivalve isolates produced the tdh gene at levels below 2%. Continuous monitoring is clearly needed to reduce seafood-borne outbreaks of disease caused by V. parahaemolyticus, and to reveal the occurrence patterns and the presence of toxic genes of the strains in different marine environments.