| Objective:Vibrio parahaemolyticus (VP) is gram-negative, halophilic bacteria, which is commonly found in seawater and seafood products. VP was first discovered in Japan in1950, and was considered the causative bacteria in food poisoning. In China, the outbreak caused by VP was ranked the highest probability of microbial foodborne disease. Ningbo is located in the southeast coast of China, where seafood consumption is rather popular and people prefer raw or undercooked seafood. Therefore, VP infection is quite common in Ningbo. By conducting O and K antigen serum agglutination testing on stool specimens collected from patients with acute diarrhea in Ningbo beilun region, we found the serotype distribution of VP in Ningbo beilun area. We carried out virulence genetic testing and molecular typing analysis in order to provide information on the molecular epidemiology for the early prevention and the control of VP. The result also provided a basis for ongoing monitoring study and laid out the foundation for further research.Method:Consecutive stool samples were collected from outpatients with acute diarrhea in Beilun District People’s Hospital from April2012to October2012. Bacterial pathogens were detected by routine culture procedures. The O/K serotypes, virulence gene and sequence types of the VP isolates were also determined.Results:1. From April to October of2012, we collected962stool specimens from patients with diarrhea. A total of71VP strains were isolated. The separation rate was7.4%(71/962), which was ranked second in bacterial pathogens. The ratio of infection cases of male to female was1.73:1(45cases:26cases). The age range of patients was from16to61years old but was mainly concentrated between20and45years old (69.0%,49/71).2. There were16combinations of O and K serogroups. Among these groups, O3:K6(44,62.0%) was ranked first, followed by O4:K8(5,7.0%) and O1:K56(3,4.2%). There were three strains that we failed to identify and they were categorized as OUT:KUT.3. All VP strains were positive for the tlh,98.6%strains were positive for tdh, and only three strains for trh were positive.67strains were tlh+tdh+trh-, three strains were tlh+tdh+trh+while only1strain was tlh+tdh-trh-. There were47strains (66.2%) VP isolates belonging to the pandemic group strains (tdh+, trh-and toxRS/new+) and24(33.8%) non-pandemic group strains. There were36pandemic group strains carrying orf8gene, which took up76.6%of all the pandemic group strains.4. We analyzed a total of71isolates and found13different STs. The most prevalent genotypes were ST3(45,63.4%), followed by ST88(5), ST479(4), ST8(4) and ST120(4), ST176, ST199, ST216, ST332, ST417, ST610, ST712and ST80.Conclusion:1. The detection rate of VP patients with acute diarrhea was (high and) up to7.4%in beilun District in Ningbo. Therefore, it is necessary to carry out VP detection in cases of diarrhea in the area. The detection could reduce the occurrence and control the propagation of foodborne illness caused by VP.2. TDH was the main causative factor of VP infection in Beilun, Ningbo. Pandemic group strain was the main epidemic strain over this area. Serotype03:K6VP was the superior strain.3. Discovered by MLST typing, ST3covered the largest number on all the patients with acute diarrhea in Ningbo and was the most dominant type. The main advantageous type was consistent with the popular type in other countries. Because of the variety of its subtypes, VP epidemic was a major cause of high prevalence in Ningbo region. |
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