Enumeration and characterization of Vibrio ssp isolates from bivalve molluscs in Vietnam

Eighty-six bivalve mollusc samples (Crassostrea gigas n=39 and Meretrix lyrata n=47) were collected from October 2015 to June 2016 in two fish markets and two supermarkets in Hanoi, Vietnam and were subjected to detection of... [ view full abstract ]

Eighty-six bivalve mollusc samples (Crassostrea gigas n=39 and Meretrix lyrata n=47) were collected from October 2015 to June 2016 in two fish markets and two supermarkets in Hanoi, Vietnam and were subjected to detection of pathogenic Vibrio species (V. cholerae, V. parahaemolyticus and V. vulnificus) through conventional cultural methods, followed by PCR identification and characterization of isolates, and to enumeration of total and potentially pathogenic V. parahaemolyticus by means of an in-house validated colony hybridization method. 

Potentially pathogenic Vibrio species were detected in 23 samples: three Meretrix samples (3.5%) showed the presence of non-O1/non-O139 V. cholerae, 23 samples (10 oyster and 13 clam samples, total 26.7%) were positive for V. parahaemolyticus, with two isolates showing the presence of trh gene; V. vulnificus was never detected. With regards to the colony hybridization results, the strains carrying tdh and/or trh genes was detected in 22 samples (25.6%) with values ranging from <10 to 4400 cfu/g (median 120 cfu/g), and the prevalence of total V. parahaemolyticus in the samples was 76.7% (range <10 – 66000 cfu/g, median 1030 cfu/g). For both potentially pathogenic and total V. parahaemolyticus, prevalence, median and maximum quantitative values were higher in Meretrix than in Crassostrea and in samples taken from supermarket compared to samples from fish market, but differences were not statistically significant.

Research founded by the Italian Ministry of Foreign Affairs and International Cooperation (Project PGR00159) and by the Vietnamese Ministry of Science and Technology (grant 06/2014/HĐ-NĐT).