| Summary |
Rangia cuneata is a brackish water clam found commonly in the estuaries of the Atlantic and Gulf Coasts. There has been recent interest in North Carolina in commercial harvesting and processing of this clam for human consumption. This research was a microbiological investigation of Rangia to determine whether its bacterial flora, which is of greater density than other edible shellfish, posed a unique threat to public health. Clams, water, and sediment were collected monthly for one year from four sites in Albemarle Sound. Microbiological examination of samples included enumeration of bacteria indicative of fecal contamination as well as screening for potentially pathogenic bacteria. The analysis of 48 Rangia samples showed a median fecal coliform most probable number (MPN) of only 80 FC/lOOg, considerably below the 230 FC/lOOg standard of federal and state regulation. Under these regulations a maximum of 10% of the samples may exceed 330 FC/lOOg, but 21% of the Rangia collections exceeded this value. In most clam samples exceeding 330 FC/iOOg, the total coliform values for the overlying water were also in excess of those allowable for shellfish growing waters. These findings indicate that Rangia did not maintain high levels of these indicator organisms, but rather reflected the bacteriological quality of the ambient water. Standard plate counts (SPC) for clams approached and sometimes exceeded 500,000 SPC/g. This value is used by some markets as an indicator of bacterial spoilage of a product. The SPC is of little sanitary significance in evaluating freshly harvested shellfish unless the number of fecal indicator organisms or pathogenic bacteria are considered. There was no statistical correlation between clam SPC's and either the numbers of indicator organisms or pathogens detected. Potentially pathogenic bacteria, when recovered, were at very low, non-infective levels. Neither Salmonella nor Shigella were confirmed in any clam samples. Staphylococcus was detected in only 5 of 40 Rangia samples at values far below those which produce significant levels of enterotoxin. Vibrio counts as high as 4,500/g of clam were recorded. However, this bacterium is very common in marine and estuarine waters and shellfish. While particular strains of V. parahaemolytlcus can cause gastrointestinal disorder, outbreaks of foodborne disease attributed to this organism are infrequent in this country. These findings indicate that when Rangia cuneata is harvested from approved waters, there is no unique threat to public health caused by its bacterial flora. Large scale routine coliform testing should be continued to supplement and verify the coliform results reported in this research. |
| Local note | Joyner-"Presented to the faculty of the Department of Biology ... in partial fulfillment of the requirements for the degree Master of Science in Biology." |
| Local note | Joyner-"Presented to the faculty of the Department of Biology ... in partial fulfillment of the requirements for the degree Master of Science in Biology." |
| Local note | Joyner-"Presented to the faculty of the Department of Biology ... in partial fulfillment of the requirements for the degree Master of Science in Biology." |
| General note | Presented to the Faculty of the Department of Biology |
| General note | Advisor: Bernard E. Kane, Jr. |
| Dissertation note | M.S. East Carolina University |
| Bibliography note | Includes bibliographical references (leaves 36-40). |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
