Quantitative analysis and gene typing of Vibrio vulnificus in sea shellfish from Zhoushan market

Objective To understand the contamination of Vibrio vulnificus in sea shellfish and the types of related virulence gene in Zhoushan. Methods By using 3% sodium chloride alkaline peptone water, the enrichment of bacteria was conducted, V. vulnificus in sea shellfish was isolated with mCPC Agar Base and suspected colonies were identified by using API20E, the quantitative detection of V. vulnificus was done with most probable number method and PCR was conducted for identification of biotype Ⅰ, type Ⅱ and serotype E of the strains and genotyping of virulence genes of vcg,16srRNA. Results Totally 64 strains of V. vulnificus in 179 samples were detected, the positive rate was 35.75%. The detection rate in summer was highest(68%) and the differences in detection rates in different seasons had statistical significance.(2=35.23,P0.05). Thirty nine strains were hemolysin gene A(vvhA) nucleic acid positive, in which 1 belonged to BT2 type,1 belonged to serotype E and other 37 strains belonged to BT1. The genotyping of virulence gene vcgC/E and 16S rRNA A/B indicated CB type was detected 31 strains, CAB type in 4 strains, EA type in 3 strains and EAB type in 1 strain. Conclusion The contamination of V. vulnificus in sea shellfish was serious in Zhoushan, especially during summer and autumn. The types of virulence genes of the pathogen showed diversity, CB type was predominated. It is necessary to conduct the risk evaluation of sea shellfish food to prevent the outbreak of food borne diseases.