The evaluation of four recent culture-based methods for the isolation and enumeration of Vibrio vulnificus bacteria from oyster meat

• Examined four methods of isolating and quantifying Vibrio vulnificus in oysters
• VVX determined to be most accurate
• “Triple plating” accurate without PCR step
• Only CPC + detected all of the C-genotype strains of V. vulnificus.
• TCBS medium fails to detect many V. vulnificus isolates.

The most common cause of seafood-borne death in the United States is the bacterium Vibrio vulnificus which can be concentrated into high numbers in the tissues of oysters or other shellfish. The ability to quickly, accurately, and inexpensively isolate living strains of this organism from oyster tissues is crucial for effective research on this pathogen. In this report, we evaluate four methods for isolating and quantifying V. vulnificus from oyster tissues, the solid media CPC + (a refined version of cellobiose–polymyxin B-colistin medium), CHROMagar Vibrio, VVX (Vibrio vulnificus X-gal), and a method termed “Triple plating”. Up to 1225 presumptive isolates were detected by each method, and 335 were subjected to molecular typing. The selectivity and sensitivity of each method was examined and VVX was found to be the most accurate method, with each of the other methods being recommended for task-specific uses. CHROMagar Vibrio is recommended for ease of use and relative accuracy, CPC + is best used to differentiate between clinically associated and environmental strains.