No abstract

Neuroblastoma cells in culture were used to detect sodium channel-specific marine toxins based on an end-point determination of mitochondrial dehydrogenase activity. The assay responds in a dose-dependent manner to ciguatoxins, brevetoxins, and saxitoxins, and delineates the toxic activity as either sodium channel enhancing or sodium channel blocking. The assay responds rapidly to sodium channel activating toxins, allowing dose dependent detection in 4 to 6 h. Brevetoxins can be detected at 250 pg, and purified ciguatoxins are detected in the low picogram and subpicogram levels. The results obtained from cell bioassay of ciguatoxic finfish extracts correlates with those obtained from mouse bioassays. Sodium channel blocking toxins can also be detected with an approximate sensitivity of 20 pg in 24 to 48 h. This cell-based technique is simple, sensitive, demonstrates potential as an alternative to animal testing for sodium channel activating and blocking toxins, and can be automated.

Vibrio vulnificus was isolated from United States West Coast estuaries at a low frequency (5.9%) from 529 samples of water, shellfish, and sediment. Four strains tested with iron-treated mice had 50% lethal dose values ranging from 7.6 to 360 CFU, compared with a 50% lethal dose of 4.9 CFU for a clinical isolate that caused the death of a septicemic patient. The presence of this pathogen may be a hazard to users of marine beaches and consumers of raw shellfish on the West Coast, especially to persons most susceptible to V. vulnificus septicemia. Species-specific antiflagellar serum and a gene probe for cytotoxin-hemolysin production were useful for screening these environmenta.l isolates. A halophilic, lactose-fermenting Vibrio species, first described in 1976 as causing septicemia in a human patient (8),

Listeria species and L. monocytogenes were found in 81 and 62%, respectively, of fresh or low-salinity waters (37 samples) in tributaries draining into Humboldt-Arcata Bay, Calif., during a winter (January-February) sampling period. The incidence of Listeria species and L. monocytogenes in sediment (46 samples) from the same sites where water was sampled was 30.4 and 17.4%, respectively. One of three bay water samples contained Listeria species (including L. monocytogenes), while of 35 samples of oysters examined, only 1 was found positive for Listeria species (L. innocua). A given species or L. monocytogenes serogroup appeared to predominate in fresh water when domesticated animals (cows, horses) were nearby, whereas greater variety with no species predominance was observed in areas with no direct animal influence.

The incidence of Vibrio cholerae in shellfish, sediment, and waters of California, Oregon, and Washington was determined during the summer of 1984. Samples from 24 distinct estuaries were analyzed qualitatively. V. cholerae non-Ol was found in 23 estuaries and in 44.6% of the 529 samples examined. V. cholerae 01 Inaba was isolated from water samples in Morro Bay, Calif. Vibrio mimicus was found in 2.3% of the samples. Cholera enterotoxin was not found in cell-free filtrates of the 100 isolates tested in the Y-1 mouse adrenal cell assay, but heat.labile cytotoxic activity was observed with 3% of the isolates. Members of the genus Vibrio have recently emerged as a substantial public health threat to consumers of seafood, particularly raw shellfish (4, 5, 8, 22-24, 28). The widespread distribution of Vibrio cholerae along the Atlantic and Gulf Coasts of the United States is well documented (6, 10, 11, 14, 15); however, determination of the incidence of V. cholerae on the U.S. West Coast has been limited to a few studies in Oregon (27) and California (17, 18), with no isolations from shellfish obtained from these waters. To date, there has been no systematic search for V. cholerae along the entire West Coast. The objective of the present study was to determine the incidence of V. cholerae in some of the many estuaries of this region. MATERIALS AND METHODS Sampling sites. Between June and October 1984, 261 sites were sampled in California, Oregon, and Washington (Fig. 1). 'Shellfish, sediment, and water samples were collected from estuaries listed in Table 1. Many sites were sampled daily for up to 4 days per estuary. Criteria for site selection included availability of shellfish, proximity to suspected pollution sources, classification according to the National Shellfish Sanitation Program, and hydrographical factors. The general strategy was to sample major freshwater sources of each estuary at the point of detectable salinity (21.0%o)