Ribotyping of Vibrio parahaemolyticus isolates obtained from food poisoning outbreaks in Taiwan

Prevalence and potential pathogenicity of Vibrio parahaemolyticus in Chinese mitten crabs (Eriocheir sinensis) harvested from the River Thames estuary, England

Chinese mitten crabs (Eriocheir sinensis) have been described as an alien invasive species in the River Thames, United Kingdom, and elsewhere in Europe. The crabs can cause considerable physical damage to the riverbeds and threaten native ecosystems. Trapping has been considered an option, but such attempts to control mitten crab populations in Germany in the 1930s failed. In the United Kingdom, it has been suggested that commercial exploitation of the species could be employed as a control option. This study was conducted as part of a larger program to assess the suitability of a commercial Chinese mitten crab fishery in the River Thames. Crabs and water samples from the River Thames between 2003 and 2006 were examined for the human pathogenic bacterium Vibrio parahaemolyticus. All samples throughout this testing period were positive for V. parahaemolyticus. The putative pathogenicity markers, thermostable direct hemolysin and thermostable direct-related hemolysin, were detected in one sample, indicating that the crabs possessed the potential to cause V. parahaemolyticus-associated illness if consumed without further processing. Levels of V. parahaemolyticus were higher during the summer than in the winter. This is the first study of V. parahaemolyticus prevalence in European-adapted Chinese mitten crabs.

A pulsed-field gel electrophoresis typing scheme for Vibrio parahaemolyticus isolates from fifteen countries

Vibrio parahaemolyticus is an important foodborne pathogen in Taiwan and many other maritime Asian countries where seafood is frequently consumed. A total of 535 strains of V. parahaemolyticus were recovered mostly (97%) from clinical samples obtained in Taiwan or in 14 other countries. These strains were typed by pulsed-field gel electrophoresis following SfiI digestion and a typing scheme was generated. The 115 different patterns identified were grouped into 13 types with dissimilarity values less than 15, plus 16 miscellaneous patterns not grouped into any of the types. Types I, A, D and J contained the most patterns, with the numbers of patterns being 17, 13, 12, and 11, respectively. However, types I, B, D, A, H and C contained the most strains, with the numbers of strains being 204, 73, 71, 54, 29 and 25, respectively. Type I consisted exclusively of the pandemic O3:K6 strains and genetically closely related strains. This PFGE typing scheme for V. parahaemolyticus could be used for the characterization of pathogenic isolates.

Pulsed-field gel electrophoresis analysis of Vibrio vulnificus strains isolated from Taiwan and the United States

Vibrio vulnificus is a marine bacterium that causes human wound infections and septicemia with a high mortality rate. V. vulnificus strains from different clinical and environmental sources or geographic regions have been successfully characterized by ribotyping and several other methods. Pulsed-field gel electrophoresis (PFGE) is a highly discriminative method, but previous studies suggested that it was not suitable for examining the correlation of V. vulnificus strains from different origins. We employed PFGE to determine its efficacy for characterizing V. vulnificus strains from different geographic regions, characterizing a total of 153 strains from clinical and environmental origins from the United States and Taiwan after SfiI or NotI digestion. V. vulnificus strains showed a high intraspecific diversity by PFGE after SfiI or NotI digestion, and about 12% of the strains could not be typed by the use of either of these enzymes. For PFGE with SfiI digestion, most of the clinical and environmental strains from the United States were grouped into cluster A, while the strains from Taiwan were grouped into other clusters. Clinical strains from the United States showed a higher level of genetic homogeneity than clinical strains from Taiwan, and environmental strains from both regions showed a similarly high level of heterogeneity. PFGE with NotI digestion was useful for studying the correlation of clinical strains from the United States and Taiwan, but it was not suitable for analyzing environmental strains. The results showed that PFGE with SfiI digestion may be used to characterize V. vulnificus strains from distant geographic regions, with NotI being a recommended alternative enzyme.

Evaluation of typing of vibrio parahaemolyticus by three PCR methods using specific primers

Vibrio parahaemolyticus is a halophilic bacterium frequently involved in human outbreaks of seafood-associated gastroenteritis. For epidemiological purposes, different molecular typing methods, such as pulsed-field gel electrophoresis (PFGE) or ribotyping, have been developed for this pathogen; however, these methods are mostly labor-intensive and time-consuming. In this work, we designed and evaluated three rapid PCR typing methods for this pathogen using primers designed on the basis of the following specific sequences: conserved ribosomal gene spacer sequence (RS), repetitive extragenic palindromic sequence (REP), and enterobacterial repetitive intergenic consensus sequence (ERIC). Typing patterns and clustering analysis indicated that these methods apparently differentiated V. parahaemolyticus strains from reference strains of interspecific Escherichia coli, V. cholerae, and V. vulnificus and were also valuable in subspecies typing of this pathogen. Forty domestic strains of V. parahaemolyticus, representing a wide range of PFGE patterns, were grouped into 15, 27, and 27 patterns, with discrimination indexes of 0.91, 0.97, and 0.98, by RS-, REP-, and ERIC-PCR, respectively. The discriminative abilities of these PCR methods closely approached or even exceeded those of PFGE and ribotyping. REP-PCR is preferable to ERIC-PCR because of the greater reproducibility of its fingerprints, while RS-PCR may be a practical method because it generates fewer amplification bands and patterns than the alternatives.