Biological Polymorphism And Antibiotic Resistance Research Of Vibrio Parahaemolyticus In Shandong Province

Background:Vibrio parahaemolyticus was first discovered in japan in 1951. It is the most frequently occurring foodborne pathogenic bacterium. Ingestion of bacteria in raw or undercooked seafood is the predominant cause of the acute gastroenteritis caused by V. parahaemolyticus. Since the outbreaks caused by Vibrio parahaemolyticus infection tend to be more concentrated during these years, it is of great significance to investigate the antibiotic-resistances and characteristics of various phenotypes in Vibrio parahaemolyticus.Objective:With investigations in distribution, virulence analysis, antibiotic resistance test, bacteria serological detection and biological homology analysis in Vibrio parahaemolyticus, gain insights in terms of Vibrio parahaemolyticus termination, distribution, and provide theoretical basis for food-safety and food supervision, establish PFGE fingerprint database of Vibrio parahaemolyticus, give support to foodborne diseases predictions.Methods:Food strains and clinical strains were isolated from aquatic products in 17 different regions and the feces of diarrhea patients in 15 surveillance hospitals of Shandong province. PCR was carried out to study the occurrence of the virulence genes in strains identified from both food and clinics. The antibiotic resistance levels of the experimental strains were determined by antibiotic resistance tests using 8 different antibiotic agents. Strains with virulence genes were serotyped by commercial antisera. Pulsed-field gel electrophoreses analysis results had been imported and analyzed by BioNumerics software.Results:Of 1969 food samples, including squid, tuna, crab, shrimp, and bivalves, such as oysters and clams, from 17 regions in Shandong province,210 strains were identified as Vibrio parahaemolyticus, accounting for 10.69%. The positive rate in identification reached to the peak in 2013 in terms of time, and the raw bivalves had the highest positive rate in different marine products, which was 18.03%.Of 3000 feces samples from diarrhea patients in 15 surveillance hospitals of Shandong province,97 strains were identified as Vibrio parahaemolyticus, accounting for 3.2%.The PCR test results claimed that 322 food strains and 97 clinical strains carry species-specific gene tlh,16 (4.97%)of food strains carry only one of the virulence genes, most (63.16%) of clinical strains carry two of the virulence genes, 23(24.21%) strains carry two, and 12(12.63%) carry three virulence genes.The antibiotic resistance test results showed that only 3 out of 101 food strains were resistant to antibiotic agents, accounting for 2.97% food strains. Those strains were all monoresistant, including 1 Cefepime resistant strain (0.99%) and 2 Sulfamethoxazole resistant strains (1.98%).95 out of 97 clinical strains were sensitive to antibiotic agents.Serological analysis showed that among 45 food strains, there were 21 strains belonging to 17 different serotypes, including 3 O2:K28 strains,2 O11:K22 strains, and 2 O5:K30 strains.97 clinical strains belonged to 8 different serotypes within 5 groups, and O3:K6 was the prevalent serotype.According to the analysis result from BioNumerics software, clinical strains can be divided into 9 groups by Sfi I.67.42%(60) strains were in G group. The clinical strains showed a higher homology.Conclusion:The Vibrio parahaemolyticus contamination in Shandong province has witnessed a gradual rise from 2010 to 2014, especially severe in inland areas. According to virulence analysis, Vibrio parahaemolyticus from food have lower virulence ability comparing with the strains from clinics. But the antibiotic susceptibilities of both strains are found to be in the same levels that strains are all sensitive to most antibiotic agents. There are various serotypes among strains identified from food, while in clinical strains the prevalent type is obviously O3:K6 serotype. Sfi I was involved in the separation test and the strains were divided into different groups using pulsed-field gel electrophoreses (PFGE), and Sfi I could separate sporadic strains from the pandemic strain in clinical strains.