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

Abstract

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 stx1 or stx1d 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.

Molecular Profiling of Shiga Toxin-Producing Escherichia coli and Enteropathogenic E. coli Strains Isolated from French Coastal Environments

“…Most of the strains used in this study were isolated between February 2013 and January 2015 from three French shellfish-harvesting areas and their watersheds, located on the English Channel coast (47). Three strains were isolated from other French shellfish-harvesting areas in 2006 (48). A total of 28 STEC and 75 EPEC strains belonging to 68 distinguishable serotypes isolated from three types of shellfish (oysters, mussels, and cockles) and from freshwater, seawater, and surface sediment samples were investigated.…”

Animal Reservoirs of Shiga Toxin-ProducingEscherichia coli

“…Shellfish, due to their filter feeding ability, pose a significant risk to human infection since they can concentrate and retain pathogens (4,130). Numerous studies have reported the recovery of both O157 and non-O157 STEC from the carcass of fish and shellfish offered for sale (131)(132)(133)(134)(135).…”

“…Dead-end hosts, as the name suggests, are incapable of transmitting STEC naturally to other animals. In the absence of evidence that aquatic species such as finfish and shellfish transmit the organism to other animals, they may act as dead-end hosts for STEC, only transmitting STEC when they are consumed (4)(5)(6).…”

<i>Escherichia coli</i> in seafood: A brief overview

“…Gourmelon et al [38] suggested that shellfish collected in coastal environments can serve as a vehicle for Shiga toxin-producing E. coli transmission. These authors analyzed samples of mussels (Mytilus edulis and Mytilus galloprovincialis), oysters (Crassostrea gigas) and cockles (Cerastoderma edule) collected from coastal and estuarine environments, and performed the first isolation of ETEC stx1d strains in France.…”