Recent innovation in microbial source tracking using bacterial real-time PCR markers in shellfish.

We assessed the capacity of real-time PCR markers to identify the origin of contamination in shellfish. Oyster, cockles or clams were either contaminated with fecal materials and host-associated markers designed from Bacteroidales or Catellicoccus marimammalium 16S RNA genes were extracted from their intravalvular liquid, digestive tissues or shellfish flesh. Extraction of bacterial DNA from the oyster intravalvular liquid with FastDNA spin kit for soil enabled the selected markers to be quantified in 100% of artificially contaminated samples, and the source of contamination to be identified in 13 out of 38 naturally contaminated batches from European Class B and Class C areas. However, this protocol did not enable the origin of the contamination to be identified in cockle or clam samples. Although results are promising for extracts from intravalvular liquid in oyster, it is unlikely that a single protocol could be the best across all bacterial markers and types of shellfish.

Chlorophyll a might structure a community of potentially pathogenic culturable Vibrionaceae. Insights from a one-year study of water and mussels surveyed on the French Atlantic coast.

The present study focused on the isolation of culturable bacteria from mussels and sea water to identify Vibrionaceae potentially pathogenic for humans. Three sites located on the French Atlantic coast were monitored monthly (twice each month during summer) for 1 year. Environmental parameters were surveyed (water temperature, salinity, turbidity, chlorophyll a) and bacteria were detected by culture and identified by API 20E(®) systems (BioMérieux) and PCR. A total of seven species were detected (Grimontia hollisae, Photobacterium damselae, Vibrio alginolyticus, V. cholerae, V. fluvialis, V. vulnificus and V. parahaemolyticus) and species diversity was higher at the end of summer. Surprisingly, V. cholerae non-O1/non-O139 was detected in spring. No site effect was detected. Using Sørensen similarity indices and statistical analyses, we showed that chlorophyll a had a significant influence on the bacterial community detected in mussels and assemblages were more similar to one another when chlorophyll a values were above 20 µg l(-1) . No significant effect of any parameter was found on the community detected in water samples. Such surveys are essential for the understanding of sanitary crises and detection of emerging pathogens.

First isolation of Shiga toxin 1d producing Escherichia coli variant strains in shellfish from coastal areas in France.

AIMS: This study was carried out to evaluate the presence of Shiga toxin-producing Escherichia coli (STEC) and E. coli O157:H7 in shellfish from French coastal environments. METHODS AND RESULTS: Shellfish were collected in six growing areas or natural beds (B category) and nonfarming areas (D category) from July 2002 to August 2004. PCR detection of stx genes was performed on homogenized whole shellfish and digestive gland tissues enrichments. STEC strains were detected by colony DNA hybridization using a stx-specific gene probe and E. coli O157 strains were additionally searched by immunomagnetic separation with O157-specific magnetic beads. Stx genes were detected in 40 of 144 (27.8%) sample enrichments from mussels, oysters or cockles, 32 of 130 enrichments (24.6%) were from B-category areas and eight of 14 (57.1%) from the D-category area. Five strains carrying stx(1) or stx(1d) genes and one stx negative, eae and ehxA positive E. coli O157:H7 were isolated from six of 40 stx-positive enrichments. No relation was found between the total E. coli counts in shellfish and the presence of STEC strains in the samples. CONCLUSIONS: The STEC strains of different serotypes and stx types are present in shellfish from French coastal environments. It is the first isolation of STEC stx1d strains in France. SIGNIFICANCE AND IMPACT OF THE STUDY: Shellfish collected in coastal environments can serve as a vehicle for STEC transmission.