Occurrence of Bacterial Pathogens and Human Noroviruses in Shellfish-Harvesting Areas and Their Catchments in France

Abstract

During a 2-year study, the presence of human pathogenic bacteria and noroviruses was investigated in shellfish, seawater and/or surface sediments collected from three French coastal shellfish-harvesting areas as well as in freshwaters from the corresponding upstream catchments. Bacteria isolated from these samples were further analyzed. Escherichia coli isolates classified into the phylogenetic groups B2, or D and enterococci from Enterococcus faecalis and E. faecium species were tested for the presence of virulence genes and for antimicrobial susceptibility. Salmonella members were serotyped and the most abundant serovars (Typhimurium and its monophasic variants and Mbandaka) were genetically characterized by high discriminative subtyping methods. Campylobacter and Vibrio were identified at the species level, and haemolysin-producing Vibrio parahaemolyticus were searched by tdh- and trh- gene detection. Main results showed a low prevalence of Salmonella in shellfish samples where only members of S. Mbandaka were found. Campylobacter were more frequently isolated than Salmonella and a different distribution of Campylobacter species was observed in shellfish compared to rivers, strongly suggesting possible additional inputs of bacteria. Statistical associations between enteric bacteria, human noroviruses (HuNoVs) and concentration of fecal indicator bacteria revealed that the presence of Salmonella was correlated with that of Campylobacter jejuni and/or C. coli as well as to E. coli concentration. A positive correlation was also found between the presence of C. lari and the detection of HuNoVs. This study highlights the importance of simultaneous detection and characterization of enteric and marine pathogenic bacteria and human noroviruses not only in shellfish but also in catchment waters for a hazard assessment associated with microbial contamination of shellfish.

Campylobacter armoricus sp. nov., a novel member of the Campylobacter lari group isolated from surface water and stools from humans with enteric infection

“…The purpose of the present One-Health-based study, conducted from 2013 to 2016, was to investigate the importance of the water-related transmission and recirculation of isolates of members of the genus Campylobacter from the C. lari group [7] in the La Fresnaye coastal catchment area located in the north-eastern part of Brittany (Côtes d'Armor department, France). The La Fresnaye catchment corresponds to a 121 km 2 area, characterized by intensive livestock (cattle and swine) and poultry farming, with a human population of about 6900 inhabitants [8,9]. Specific focus was given to the presence of the bacteria in shellfish-producing areas downstream of the coastal catchment, the diversity found in the catchment's rivers and seawater, the faecal carriage among wildfowl and the related incidence in the French human population.…”

“…In an evaluation of the prevalence of species of the genus Campylobacter in three French coastal catchments, including the La Fresnaye catchment, species of the genus Campylobacter were recovered from 58.3% (n=228) of water samples and 26.6% (n=238) of shellfish samples [9].…”

AB_SA: Tracing the source of bacterial strains based on accessory genes. Application toSalmonellaTyphimurium environmental strains

“…Salmonella strains are frequently detected in surface water samples, e.g. 30.1% of samples from three French coastal catchments (31), 43% of samples from Georgia (USA) (36) and 23% of samples from Canada (37). Among Salmonella serovars, Salmonella Typhimurium and its monophasic variants were isolated more frequently in some sites than others (31).…”

“…30.1% of samples from three French coastal catchments (31), 43% of samples from Georgia (USA) (36) and 23% of samples from Canada (37). Among Salmonella serovars, Salmonella Typhimurium and its monophasic variants were isolated more frequently in some sites than others (31). Pigs, poultry, and ruminants (e.g., cattle) constitute a relevant source of these pathogens acting as natural Salmonella reservoirs and without showing any symptoms while shedding into the environment (38).…”

“…For the strains to attribute, 29 strains of Salmonella were isolated from the environment (e.g., fresh or brackish water and soil) from both ANSES and IFREMER with the collaboration of the University of Caen (France). The IFREMER’s environmental isolates originate from a research project (31). They were isolated from freshwater (n=12) in Brittany and brackish water in Normandy (n=3).…”