Value of Cellobiose-Polymyxin B-Colistin Agar for Isolation of Vibrio vulnificus from Oysters.

Twenty-eight samples, comprising a total of 224 oysters, were examined for the presence of Vibrio vulnificus . Oyster homogenates were plated onto cellobiose-polymyxin B-colistin (CPC) agar or V. vulnificus enumeration (VVE) agar, with subsequent hybridization with a gene probe specific for this pathogen. Of over 3,500 cellobiose-positive colonies initially tested from CPC agar, 28.7% could be identified as V. vulnificus on the basis of probe hybridization. Of the 19,000 colonies developing on VVE agar, only 2.8% were identified as this species. When in subsequent CPC agar studies colony morphology as well as color was considered, 81.6% of over 1,000 colonies probed proved to be V. vulnificus . We conclude that CPC agar is highly selective for this pathogen, and may be effectively employed in monitoring studies to determine levels of this bacterium in molluscan shellfish.