Prevalence of Vibrio parahaemolyticus in oyster and clam culturing environments in Taiwan

• Published in: International journal of food microbiology 2013-01, Vol.160 (3), p.185-192
• Main Authors: Yu, Wei-Ting, Jong, Koa-Jen, Lin, Yu-Ren, Tsai, Shing-en, Tey, Yao Hsien, Wong, Hin-chung
• Format: Article
• Language: English
• Subjects: Animals; Aquaculture; Bacterial Load; Biological and medical sciences; Bivalvia - microbiology; Clam; Culture; Environmental Monitoring; Environments; Fish and seafood industries; Food industries; Food Microbiology; Fundamental and applied biological sciences. Psychology; Geologic Sediments - microbiology; Marine; Ostreidae - microbiology; Oyster; Salinity; Seawater - microbiology; Taiwan; Vibrio; Vibrio - enzymology; Vibrio - genetics; Vibrio - isolation & purification; Vibrio - physiology; Vibrio parahaemolyticus; Vibrio parahaemolyticus - enzymology; Vibrio parahaemolyticus - genetics; Vibrio parahaemolyticus - isolation & purification; Vibrio parahaemolyticus - physiology
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2012.11.002

Vibrio parahaemolyticus is the most prevalent gastroenteritis pathogen in Taiwan and some other Asian countries, and it frequently occurs in oysters and other seafood. This study monitors changes in the density of V. parahaemolyticus and environmental parameters in oyster and hard clam aquacultural environments in Taiwan. Water, sediment and shellfish samples were collected from five sampling sites in 2008–2010, and analyzed for environmental physiochemical parameters, numbers of indicator bacteria (total aerobic counts, total coliforms and fecal coliforms), Vibrio and V. parahaemolyticus present. The results for open oyster farms and hard clam ponds did not differ significantly. V. parahaemolyticus was detected in 77.5, 77.5, 70.8 and 68.8% of the water, sediment, oyster and clam samples, respectively. The densities of V. parahaemolyticus were significantly higher in shellfish than in sediment or water samples, with mean values of 1.33, 1.04 and −0.02 Log CFU/g, respectively. Among these five sampling sites, Shengang and Fangyuan yielded significantly different data from those obtained at the other three sites. As determined by linear multiple regression, V. parahaemolyticus density in water samples depended significantly on the precipitation and Vibrio count, while the V. parahaemolyticus density in the sediment or shellfish samples depended significantly on the salinity of the seawater. Among 1076 isolates examined, a total of three putative pathogenic isolates were identified from 2.5% of the examined samples, and these isolates exhibited hemolytic or urease activities and the presence of gene markers for tdh, trh, type III secretion system (T3SS) 1 (vcrD1) or T3SS2α (vcrD2). The results herein may facilitate the assessment of risk associated with this pathogen in Taiwan and other geographically similar regions. ► First report on the V. parahaemolyticus density vs other factors in Taiwan. ► V. parahaemolyticus densities in open oyster farms and clam ponds were indifferent. ► V. parahaemolyticus density in seafood significantly depended on salinity. ► Six putative pathogenic strains from the environment were identified and characterized.