EFFECT OF STORAGE AND CHANGING SEA WATER ON CONTAMINATED OYSTERS

Abstract

In artificially contaminated shell oysters stored at refrigerator temperature Bacillus typhosus persisted for 49 days. On the shells of stored oysters B. typhosus could be detected for 14-40 days, depending on the degree of contamination. A dead oyster serves as a culture medium and the number of B. typhosus will increase if the temperature is satisfactory for multiplication. Repeated changes of fresh sea water caused a rapid diminution in the numbers of B. typhosus on or in oysters. Although 99% were removed after the 3rd change of water a few persisted for a considerable period. The most important point brought out is that small numbers of B. typhosus may persist in oysters for a long period. This emphasizes the fact that the only safe oyster is one which has been protected from fecal pathogens for at least some months prior to harvesting.