Parahaemolyticus In Oysters Research Articles

Oyster-to-Oyster Variability in Levels of Vibrio parahaemolyticus

This study examined the variability in the levels of total and pathogenic Vibrio parahaemolyticus in individual oysters. Twenty oysters were collected on three occasions (in June, July, and September 2001) from a site near Mobile Bay, Ala. Ten of these oysters were tested immediately, and 10 were tested after 24 h of storage at 26°C. Levels of total and pathogenic V. parahaemolyticus were determined by alkaline phosphatase–labeled DNA probe procedures targeting the thermolabile hemolysin and thermostable direct hemolysin genes, respectively. Similar V. parahaemolyticus levels (200 to 2,000 CFU/g) were found in nearly 90% of the oysters (for all sampling occasions) prior to storage. The log-transformed densities (means ± standard deviations) of V. parahaemolyticus in oysters immediately after harvest were 2.90 ± 0.91, 2.88 ± 0.36, and 2.47±0.26 log10 CFU/g for June, July, and September, respectively. After storage for 24 h at 26°C, the mean V. parahaemolyticus densities increased approximately 13- to 26-fold. Before storage, pathogenic V. parahaemolyticus was detected in 40% (10 to 20 CFU/g) of the oysters collected in June and July but was not detected in any oysters collected in September. After storage, pathogenic V. parahaemolyticus was detected in some oysters at levels of >100 CFU/g. These data should aid in the development of sampling protocols for oyster monitoring programs and in the determination of exposure distributions associated with raw oyster consumption.

Rapid detection of Vibrio parahaemolyticus in oysters by immunofluorescence microscopy

A method of indirect immunofluorescence microscopy was developed for the rapid detection of Vibrio parahaemolyticus in oysters. Affinity-purified antibodies against two outer membrane proteins (molecular mass 36 and 34 kDa, respectively) of V. parahaemolyticus were used as the primary antibodies to label the vibrio, and fluorescein isothiocyanate-conjugated goat anti-rabbit immunoglobulin G was used to reveal the antigen-antibody reaction. Of 85 strains of V. parahaemolyticus tested, all produced strong fluorescence under the fluorescence microscope. However, for 63 strains (including 27 vibrios) of other bacteria tested, 6 produced weak to moderate fluorescence. The sensitivity and specificity of the immunostaining technique were 100 and 90.5%, respectively. In the inoculation experiments, as low as 1.7 CFU g of V. parahaemolyticus spiked in oysters could be detected by the immunostaining method after 18-h enrichment in alkaline peptone water containing 3% NaCl. The immunofluorescence microscopy is recommended for rapid screening of V. parahaemolyticus in oysters, a presumptive positive result could be obtained within 24 h.

Effect of Temperature on Vibrio parahaemolyticus in Oysters at Refrigerator and Deep Freeze Temperatures

Vibrio parahaemolyticus in oysters may multiply to dangerous levels when the oysters are stored at temperatures greater than 8°C. The bacteria rapidly lose their viability during storage at −0°, 0° and 4°C.