First report of the intracellular fish parasite

Sphaerothecum destruens has emerged as a serious parasite of fish. Its life cycle, as well as its association with Asian cyprinids, allows it to infect a wide range of hosts. The topmouth gudgeon (Pseudorasbora parva), an invasive species that has rapidly colonized Europe, has been shown to be a healthy carrier of the parasite. However, in France, the presence of S. destruens and its possible association with P. parva have not yet been demonstrated. Here, we screened topmouth gudgeon DNA for S. destruens using PCR amplification of an 18S rRNA gene fragment of the parasite. Sequencing and phylogenetic analysis confirmed the presence of S. destruens in the invasive fish species. Our results suggest that P. parva can be a potent vector of the parasite, and has the potential to become a major ecological and economic threat to the French fish population

Uneven genotypic diversity of Escherichia coli in fecal sources limits the performance of a library-dependent method of microbial source tracking on the southwestern French Atlantic coast

International audienceTo develop a library-dependent method of tracking fecal sources of contamination of beaches on the Atlantic coast of southwestern France, a library of 6368 Escherichia coli isolates was constructed from samples of feces, from 40 known human or animal sources collected in the vicinity of Arcachon Bay in 2010, and in French Basque Country, Landes, and Beam, between 2017 and 2018. Different schemes of source identification were tested: use of the complete or filtered reference library; characterization of the isolates by genotypic or proteomic profiling based on ERIC-PCR or MALDI-TOF mass spectrometry, respectively; isolate by isolate assignment using either classifiers based on the Pearson similarity or SVM (support vector machine). With the exception of one source identification scheme, which was discarded since it used self-assignment, all tested schemes resulted in low rates of correct classification (15%). The heterogeneous coverage of E. coli genotypic diversity between sources and the uneven distribution of E. coli genotypes in the library likely explain the difficulties encountered in identifying the sources of fecal contamination. Shannon diversity index of sources ranged from 0 for several wildlife species sampled once to 3.03 for sewage treatment plant effluents sampled on various occasions, showing discrepancies between sources. The uneven genotypic composition of the library was attested by the value of the Pielou index (0.54), the high proportion of nondiscriminatory genotypes (>91% of the isolates), and the very low proportion of discriminatory genotypes (<3%). Since efforts made to constitute such a library are not affordable for routine analyses, the results question the relevance of developing such a method for identifying sources of fecal contamination on such a coastline

First report of the intracellular fish parasite Sphaerothecum destruens

Sphaerothecum destruens has emerged as a serious parasite of fish. Its life cycle, as well as its association with Asian cyprinids, allows it to infect a wide range of hosts. The topmouth gudgeon (Pseudorasbora parva), an invasive species that has rapidly colonized Europe, has been shown to be a healthy carrier of the parasite. However, in France, the presence of S. destruens and its possible association with P. parva have not yet been demonstrated. Here, we screened topmouth gudgeon DNA for S. destruens using PCR amplification of an 18S rRNA gene fragment of the parasite. Sequencing and phylogenetic analysis confirmed the presence of S. destruens in the invasive fish species. Our results suggest that P. parva can be a potent vector of the parasite, and has the potential to become a major ecological and economic threat to the French fish population