Comment répondre aux défis de la phagothérapie en élevage aquacole ?

Avec la nécessité de nourrir une population humaine estimée à 9,2 milliards en 2050 [1], les secteurs de l’élevage dont l’aquaculture ont besoin d’une alternative aux antibiotiques dont ils étaient historiquement fortement dépendants. Parmi les options envisagées pour répondre à cette demande, les bactériophages semblent apporter une réponse prometteuse : leur abondance, leur efficacité ainsi que leur spécificité sont autant d’arguments stimulant l’intérêt qu’ils suscitent. Le milieux aqueux est de plus avantageux pour la phagothérapie puisqu’il favorise les rencontre entre le virus et son hôte. De nombreux produits à base de phages et à destination des industries agricoles et agroalimentaires émergent, tels que le phage anti Listeria monocytogenes P100.Cependant ces virus ne présentent pas que des avantages puisque leur utilisation en élevage peut avoir des conséquences écologiques via la perturbation des écosystèmes microbiens, la diffusion incontrôlée de gènes de résistance aux antibiotiques ou de pathogénicité. Les bactériophages favorisent également la propagation de résistances chez leurs hôtes et doivent donc être utilisés avec précaution [2]. Excepté chez certains pays, ces antimicrobiens viraux ne rentrent dans aucune définition réglementaire et leur utilisation n’est donc pas autorisée en élevage (ni en tant qu’additif alimentaire ni en tant que traitement curatif) [3]. Enfin pour parvenir à les utiliser dans un cadre industriel, il est important de s’assurer une production sans danger. Ces problématiques sont similaires pour une utilisation des phages à but sani- taire lors de la transformation des aliments.Plusieurs leviers d’actions peuvent être envisagés pour répondre à certaines de ces limites : les phages peuvent être associés en cocktails ou combinés avec d’autres actifs afin d’augmenter leur efficacité et limiter le développement de résistances. Il est également possible de les sélectionner ou d’effectuer des modifications génétiques pour éliminer les caractéristiques non désirées. L’utilisation d’enzymes lytiques (holines et endolysines) au lieu de virions complets est une piste permettant la résolution des questions d’échanges de matériel génétique et de réglementation, puisqu’il ne s’agit alors par définition plus de virus. Concernant la production de phages, il est nécessaire d’identifier une souche de propagation non pathogène afin de produire en sécurité

Overcoming the challenges of phage therapy for industrial aquaculture: A review

Aquaculture is the fastest-growing sector in food industry. Its development is powered by the intensification ofthe production which increased bacterial disease occurrence and spreading. As aquaculture deeply relies on amassive prophylactic and therapeutic use of antibiotics, it is threatened by the emergence of multi drug resistantbacteria. The stalled development of new antibiotics makes finding new therapeutic solutions a burning issue.Thanks to their specific host range, their ability to treat both the farmed species and the environment, theirlimited ecological impact and their abundance in the environment, bacteriophages represent a promising sustainablesolution to control pathogenic aquaculture bacteria.In this review we discuss the interest of phage biocontrol for aquaculture and how can bacterial resistance,ecological, pharmacological and production related issues be solved

Toxigenic potential and antimicrobial susceptibility of Bacillus cereus group bacteria isolated from Tunisian foodstuffs

International audienceBackground: Despite the importance of the B. cereus group as major foodborne pathogens that may cause diarrheal and/or emetic syndrome(s), no study in Tunisia has been conducted in order to characterize the pathogenic potential of the B. cereus group. The aim of this study was to assess the sanitary potential risks of 174 B. cereus group strains isolated from different foodstuffs by detecting and profiling virulence genes (hblA, hblB, hblC, hblD, nheA, nheB, nheC, cytK, bceT and ces), testing the isolates cytotoxic activity on Caco-2 cells and antimicrobial susceptibility towards 11 antibiotics. Results: The entertoxin genes detected among B. cereus isolates were, in decreasing order, nheA (98.9%), nheC (97.7%) and nheB (86.8%) versus hblC (54.6%), hblD (54.6%), hblA (29.9%) and hblB (14.9%), respectively encoding for Non-hemolytic enterotoxin (NHE) and Hemolysin BL (HBL). The isolates are multi-toxigenic, harbouring at least one gene of each NHE and HBL complexes associated or not to bceT, cytK-2 and ces genes. Based on the incidence of virulence genes, the strains were separated into 12 toxigenic groups. Isolates positive for cytK (37,9%) harbored the cytK-2 variant. The detection rates of bceT and ces genes were 50.6 and 4%, respectively. When bacteria were incubated in BHI-YE at 30°C for 18 h and for 5 d, 70.7 and 35% of the strains were shown to be cytotoxic to Caco-2 cells, respectively. The cytotoxicity of B. cereus strains depended on the food source of isolation. The presence of virulence factors is not always consistent with cytotoxicity. However, different combinations of enterotoxin genetic determinants are significantly associated to the cytotoxic potential of the bacteria. All strains were fully sensitive to rifampicin, chloramphenicol, ciprofloxacin, and gentamycin. The majority of the isolates were susceptible to streptomycin, kanamycin, erythromycin, vancomycin and tetracycline but showed resistance to ampicillin and novobiocin. Conclusion: Our results contribute data that are primary to facilitate risk assessments in order to prevent food poisoning due to B. cereus group

Isolation, caracterization and use of a Vibrio spp. collection in order to develop a phage therapy product for shrimp aquaculture.

D’après l’ONU, le peuplement humain atteindra 9,7 milliards en 2050. Cette population à venir devra être accompagnée d’une augmentation de la production alimentaire don l’aquaculture est pressentie pour prendre la plus grande part. Le développement de cette industrie est cependant menacé par la diminution forcée de l’utilisation d’antibiotiques, qui sont utilisés pour traiter les maladies bactériennes comme les vibrioses. Parmi les solutions envisagées pour remplacer ces derniers, les bacteriophages (phages), qui sont des virus de bactéries, semblent prometteurs. L’objectif du projet dont le travail décrit dans ce document est la première partie est d’obtenir des phages capables de traiter les vibrioses, dans les élevages de crevettes.La première étape de la stratégie utilisée est la construction et la caractérisation d’une collection de souches de Vibrio spp. Celle-ci a été ensuite utilisée pour rechercher et caractériser des phages. Une souchothèque de 234 souches de Vibrio spp. a ainsi été assemblée. L’étude du génome de 15 de ses souches a permis la découverte de 4 nouvelles espèces. Sept variants d’un phage ont été isolés et caractérisés, notamment par l’étude de leur génome. Le plan de travail expérimental mis au point, la collection bactérienne ainsi que les recommandations pour l’obtention de phages décrites dans ce document sont un premier pas vers le développement d’un produit de phagothérapie pour l’entreprise Mixscience.Human population is going to reach 9.7 billion by 2050 according to UN. This growth needs to be followed by an increase in food production, of which aquaculture is foreseen to take the biggest part. Aquaculture industry’s growth is however threatened by the mandatory diminution of antibiotics use, which are used to treat bacterial diseases such as vibriosis. Bacteriophages (phages) are virus infecting bacteria. They are among the most promising antibiotic alternatives for aquaculture. This thesis is part of a Project that aims at gathering phages able to treat vibriosis in shrimp farms. The first step to achieve this was to build and caracterize a Vibrio spp. strain collection, which was then used to obtain phages.A 234 Vibrio spp. Strain colection was therefore built. The study of the genome of 15 strains allowed the discovery of 4 new species. And 7 phage variants were isolated and caracterized, by various techniques including genome analysis. The workflow developped in this study, the bacterial strain collection and the recommandation for phage isolation given in this document are a first step towards the developpment of a phage-based product for Mixscience company

L’IA pour des systèmes industriels interopérables et autonomes

Entretien avec Olivier Boissier, Maxime Lefrançois et Antoine ZIMMERMANN réalisé par Anaïs Culot pour I'MTech, le Blog recherche de l'Institut Mines-Télécom.À Mines Saint-Étienne, les chercheurs Olivier Boissier, Maxime Lefrançois et Antoine Zimmermann, s’attaquent à la problématique d’interopérabilité essentielle à l’industrie du futur, grâce à l’IA. La standardisation d’informations sous forme de graphes de connaissances leur permet de faire interagir des machines aux langages différents. Ils exploitent ensuite ce système via un réseau d’agents autonomes distribués sur chaque machine pour automatiser une ligne de production

Isolation and Characterization of a Novel Phage Collection against Avian-Pathogenic Escherichia coli

The increase in antibiotic-resistant avian-pathogenic Escherichia coli (APEC), the causative agent of colibacillosis in poultry, warrants urgent research and the development of alternative therapies. This study describes the isolation and characterization of 19 genetically diverse, lytic coliphages, 8 of which were tested in combination for their efficacy in controlling in ovo APEC infections. Genome homology analysis revealed that the phages belong to nine different genera, one of them being a novel genus (Nouzillyvirus). One phage, REC, was derived from a recombination event between two Phapecoctavirus phages (ESCO5 and ESCO37) isolated in this study. Twenty-six of the 30 APEC strains tested were lysed by at least one phage. Phages exhibited varying infectious capacities, with narrow to broad host ranges. The broad host range of some phages could be partially explained by the presence of receptor-binding protein carrying a polysaccharidase domain. To demonstrate their therapeutic potential, a phage cocktail consisting of eight phages belonging to eight different genera was tested against BEN4358, an APEC O2 strain. In vitro, this phage cocktail fully inhibited the growth of BEN4358. In a chicken lethality embryo assay, the phage cocktail enabled 90% of phage-treated embryos to survive infection with BEN4358, compared with 0% of nontreated embryos, indicating that these novel phages are good candidates to successfully treat colibacillosis in poultry.IMPORTANCE Colibacillosis, the most common bacterial disease affecting poultry, is mainly treated by antibiotics. Due to the increased prevalence of multidrug-resistant avian-pathogenic Escherichia coli, there is an urgent need to assess the efficacy of alternatives to antibiotherapy, such as phage therapy. Here, we have isolated and characterized 19 coliphages that belong to nine phage genera. We showed that a combination of 8 of these phages was efficacious in vitro to control the growth of a clinical isolate of E. coli. Used in ovo, this phage combination allowed embryos to survive APEC infection. Thus, this phage combination represents a promising treatment for avian colibacillosis

Isolation of Harveyi clade Vibrio spp. collected in aquaculture farms: How can the identification issue be addressed?

International audienceAquaculture is a fast growing industry with its development hampered by bacterial diseases. Vibriosis caused byHarveyi clade strains is known for causing heavy loss especially in shrimp aquaculture farms. For farm treatmentand pathogen spread management, veterinarians and researchers need reliable bacterial identification tools. Arange of identification methods have been presented for Vibrio spp. in recent literature but little feedback on theirperformance have been made available to this day.This study aims at comparing Vibrio spp. identification methods and providing guidance on their use.Fifty farms were sampled and bacterial colonies were isolated using specific culture media before microscopicanalysis and genomic profiling using ERIC-PCR. A preliminary identification step was carried out using MALDIToFmass spectrometry. Four methods were compared for strain identification on 14 newly isolated Harveyiclade Vibrio spp. strains: whole genome sequencing (digital DNA DNA Hybridization (dDDH)), 5 MLSA schemes,ferric uptake regulation (fur) and lecithin-dependent haemolysin (ldh) single gene based identification methods.Apart from dDDH which is a reference method, no technique could identify all the isolates to the species level.The other tested techniques allowed a faster, cheaper but sub genus clade identification which can be interestingwhen absolute precision is not required. In this regard, MALDI-ToF and fur based identification seemed especiallypromising

Catalogue of Geadephaga (Coleoptera: Adephaga) of America, north of Mexico

All scientific names of Trachypachidae, Rhysodidae, and Carabidae (including cicindelines) recorded from America north of Mexico are catalogued. Available species-group names are listed in their original combinations with the author(s), year of publication, page citation, type locality, location of the name-bearing type, and etymology for many patronymic names. In addition, the reference in which a given species-group name is first synonymized is recorded for invalid taxa. Genus-group names are listed with the author(s), year of publication, page citation, type species with way of fixation, and etymology for most. The reference in which a given genus-group name is first synonymized is recorded for many invalid taxa. Family-group names are listed with the author(s), year of publication, page citation, and type genus. The geographical distribution of all species-group taxa is briefly summarized and their state and province records are indicated.One new genus-group taxon, Randallius new subgenus (type species: Chlaenius purpuricollis Randall, 1838), one new replacement name, Pterostichus amadeus new name for Pterostichus vexatus Bousquet, 1985, and three changes in precedence, Ellipsoptera rubicunda (Harris, 1911) for Ellipsoptera marutha (Dow, 1911), Badister micans LeConte, 1844 for Badister ocularis Casey, 1920, and Agonum deplanatum Ménétriés, 1843 for Agonum fallianum (Leng, 1919), are proposed. Five new genus-group synonymies and 65 new species-group synonymies, one new species-group status, and 12 new combinations (see Appendix 5) are established.The work also includes a discussion of the notable private North American carabid collections, a synopsis of all extant world geadephagan tribes and subfamilies, a brief faunistic assessment of the fauna, a list of valid species-group taxa, a list of North American fossil Geadephaga (Appendix 1), a list of North American Geadephaga larvae described or illustrated (Appendix 2), a list of Geadephaga species described from specimens mislabeled as from North America (Appendix 3), a list of unavailable Geadephaga names listed from North America (Appendix 4), a list of nomenclatural acts included in this catalogue (Appendix 5), a complete bibliography with indication of the dates of publication in addition to the year, and indices of personal names, supraspecific names, and species-group names