Comparative Validity of Members of the Total Coliform and Fecal Coliform Groups for Indicating the Presence of Salmonella in the Eastern Oyster, Crassostrea virginica

Abstract

During a 24-month survey, 539 samples each of the Eastern oyster, Crassostrea virginica, and the overlying water were collected to determine the relation of most probable number (MPN) of the total and fecal coliform groups in shellfish and water to the presence of Salmonella in the shellfish themselves. Occurrence of Salmonella in the shellfish more closely paralleled a progressive increase in the fecal coliform MPN as compared to the total coliform MPN in the water and shellfish meat. The percentage of Salmonella-positive shellfish samples was somewhat higher in oysters harvested from waters conforming to the present bacteriological approved growing area standard of ≤70 total coliforms per 100 ml water as compared to these same waters meeting a recently proposed fecal coliform standard of ≤14 organisms per 100 ml. In no instance was Salmonella detected in oysters from growing areas officially approved for harvesting on the basis of both a bacteriological and sanitary survey. Of a variety of enrichment broths and plating media used for recovery of Salmonella from oysters, direct enrichment in tetrathionate broth with added brilliant green followed by streaking on bismuth sulfite agar was the most productive combination of media for recovering a large variety of Salmonella serotypes.