Contamination of shellfish-harvesting areas by fecal microorganisms constitutes a significant risk to human health. These micro-organisms can come mainly from discharges resulting from urban and agricultural activities upstream. Campylobacter is the main causative agent of human bacterial gastroenteritis. The objectives of this study were (i) to evaluate the prevalence of Campylobacter spp. in shellfish from several shellfish-harvesting areas in France and (ii) to characterize some isolates by sequencing their genomes.
Shellfish batches (n = 458) were collected from February 2013 to September 2017. The detection for Campylobacter spp. was carried out according to the EN ISO 10272 method and the species identification by MALDI-TOF. The genomes of 130 isolates of C. lari were sequenced by Illumina MiSeq. Spades (v.3.12.0) was used for assembly and SeqSphere (Ridom) for ST (sequence type) recovery.
The prevalence of Campylobacter spp. in the shellfish batches collected in Brittany (n = 120) and Normandy (n = 338) were 39.0% and 16.9%, respectively, with a higher prevalence in cockles (42.3%, n=78) compared to mussels (21%, n=190) or oysters (19.3%, n=109). A total of 400 campylobacters were isolated and C. lari was the most prevalent species (38.3% of the Brittany’s batches and 10.9% of Normandy’s batches positive for this species). This prevalence is lower for C. jejuni (1.5% and 0.8%, respectively) and C. coli (1.8% and 2.5%). The complete genome analysis of the C. lari group strains shows a high genetic diversity: presence of several species and subspecies (ie C. ornithocola, C. lari UPTC, C. lari concheus) and identification of new STs.
This study shows the presence of Campylobacter spp. in shellfish from shellfish-harvesting areas with a large diversity of isolated strains. Perspectives will focus on comparing them with clinical strains and strains from upstream rivers and various animal sources (wildlife and livestock).