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.