Bacteroides vulgatus, indicator of human fecal contamination in shellfish

Coliform Bacteria are the indicators of fecal contamination in shellfish. It may be useful to identify other bacteria that could also act as indicators. Anaerobic bacteria comprise a large portion of human intestinal flora; however their usefulness in assessing contamination in shellfish has been overlooked. Bacteroides vulgatus, a human intestinal anaerobe, has been isolated from shellfish, this suggesting its use as a potential indicator of fecal contamination. Bacteroides vulgatus was compared to a standard coliform organisms, Escherichia coli, for comparison as a indicator of fecal contamination. The survival in seawater of Escherichia coli and Bacteroides vulgatus was determined to be 72 hours for E. coli and 48 hours for B. vulgatus. E. coli, a facultative anaerobe, was recovered in higher concentrations when grown anaerobically compared with aerobic incubation. The aerotolerance of the B. vulgatus isolates was also determined. Aerotolerance varied with each isolate, some of which were recoverable following 192 hours of non-anaerobic incubation. B. vulgatus recovery was compared with total coliform and fecal coliform recoveries during the rainy season from Monterey and Tomales Bay regions. B. vulgatus was detected at the total coliform 2200 MPN (most probable number) level from water and oyster grown in Monterey and Tomales Bay regions. Fecal coliform level and B. vulgatus recoveries were similar.