La osmoregulación como factor potencial de la distribución diferencial de dos especies crípticas de góbido, Pomatoschistus microps y P. marmoratus, en las lagunas mediterráneas francesas

This study was aimed at the detection of potential differences in the osmoregulatory capacity of two cryptic species of gobies, Pomatoschistus microps (Krøyer, 1838) and P. marmoratus (Risso, 1810), that have different distributions in French Mediterranean lagoons characterised by different salinity regimes. Specimens of both species were experimentally exposed to different salinities, their salinity tolerance was evaluated and their blood osmolality was measured. Both species are strong osmoregulators over a wide range of salinities but P. microps showed higher performances of hyper-regulation at very low salinities (10 and 40 mosm/kg, i.e. freshwater 0.3 and 1.4) and of hypo-regulation at high salinities (1500 mosm/kg, 51). Only P. microps was able to tolerate freshwater exposure over 4 days. We conclude that the high osmoregulatory capacity found in P. microps is linked to its better survival at very low salinities and is a physiological requirement for living in areas such as the Mauguio lagoon where salinity is highly variable. In contrast, as osmoregulation of P. marmoratus is less efficient at extreme salinities, this species cannot colonise such environments and is restricted to habitats where salinity is more stable, such as the Thau lagoon.Este estudio tuvo por objeto la detección de diferencias potenciales en la capacidad osmorreguladora de dos especies crípticas de góbido, Pomatoschistus microps (Krøyer, 1838) y P. marmoratus (Risso, 1810), que presentan diferentes áreas de distribución en lagunas mediterráneas francesas caracterizadas por regímenes de salinidad distintos. Especímenes de ambas especies fueron expuestos experimentalmente a diferentes salinidades, evaluándose su tolerancia a la salinidad y midiéndose su osmolalidad sanguínea. Ambas especies tienen una amplia capacidad osmoreguladora en un amplio rango de salinidades. Sin embargo, en comparación con P. marmoratus, P. microps mostró mayores rendimientos hiper-regulatorios a salinidades muy bajas (10 y 40 mosm/kg, es decir agua dulce 0.3 y 1.4) e hipo-regulatorios a salinidades altas (1500 mosm/kg, 51). Sólo P. microps fue capaz de tolerar la exposición al agua dulce durante 4 días. Podemos concluir que la gran capacidad osmoreguladora encontrada en P. microps está ligada a su mayor supervivencia a salinidades muy bajas, siendo un requerimiento fisiológico para vivir en áreas tales como la laguna de Mauguio, donde la salinidad es muy variable. Por el contrario, puesto que la osmoregulación de P. marmoratus es menos eficiente en salinidades extremas, esta especie no puede colonizar tales ambientes y se ve restringida a hábitats donde la salinidad es más estable, como la laguna de Tha

Multilocus sequence typing supports the hypothesis that Ochrobactrum anthropi displays a human-associated subpopulation

<p>Abstract</p> <p>Background</p> <p><it>Ochrobactrum anthropi </it>is a versatile bacterial species with strains living in very diverse habitats. It is increasingly recognized as opportunistic pathogen in hospitalized patients. The population biology of the species particularly with regard to the characteristics of the human isolates is being investigated. To address this issue, we proposed a polyphasic approach consisting in Multi-Locus Sequence Typing (MLST), multi-locus phylogeny, genomic-based fingerprinting by pulsed-field gel electrophoresis (PFGE) and antibiotyping.</p> <p>Results</p> <p>We tested a population of 70 <it>O. anthropi </it>clinical (n = 43) and environmental (n = 24) isolates as well as the type strain <it>O. anthropi </it>ATCC49188^Tand 2 strains of <it>Ochrobactrum lupini </it>and <it>Ochrobactrum cytisi </it>isolated from plant nodules. A Multi-Locus Sequence Typing (MLST) scheme for <it>O. anthropi </it>is proposed here for the first time. It was based on 7 genes (3490 nucleotides) evolving mostly by neutral mutations. The MLST approach suggested an epidemic population structure. A major clonal complex corresponded to a human-associated lineage since it exclusively contained clinical isolates. Genomic fingerprinting separated isolates displaying the same sequence type but it did not detect a population structure that could be related to the origin of the strains. None of the molecular method allowed the definition of particular lineages associated to the host-bacteria relationship (carriage, colonisation or infection). Antibiotyping was the least discriminative method.</p> <p>Conclusion</p> <p>The results reveal a human-associated subpopulation in our collection of strains. The emergence of this clonal complex was probably not driven by the antibiotic selective pressure. Therefore, we hypothesise that the versatile species <it>O. anthropi </it>could be considered as a human-specialized opportunistic pathogen.</p

Comparative diffusion assay to assess efficacy of topical antimicrobial agents against Pseudomonas aeruginosa in burns care

<p>Abstract</p> <p>Background</p> <p>Severely burned patients may develop life-threatening nosocomial infections due to <it>Pseudomonas aeruginosa</it>, which can exhibit a high-level of resistance to antimicrobial drugs and has a propensity to cause nosocomial outbreaks. Antiseptic and topical antimicrobial compounds constitute major resources for burns care but in vitro testing of their activity is not performed in practice.</p> <p>Results</p> <p>In our burn unit, a <it>P. aeruginosa </it>clone multiresistant to antibiotics colonized or infected 26 patients over a 2-year period. This resident clone was characterized by PCR based on ERIC sequences. We investigated the susceptibility of the resident clone to silver sulphadiazine and to the main topical antimicrobial agents currently used in the burn unit. We proposed an optimized diffusion assay used for comparative analysis of <it>P. aeruginosa </it>strains. The resident clone displayed lower susceptibility to silver sulphadiazine and cerium silver sulphadiazine than strains unrelated to the resident clone in the unit or unrelated to the burn unit.</p> <p>Conclusions</p> <p>The diffusion assay developed herein detects differences in behaviour against antimicrobials between tested strains and a reference population. The method could be proposed for use in semi-routine practice of medical microbiology.</p

Highly Diversified Pandoraea pulmonicola Population during Chronic Colonization in Cystic Fibrosis

Several environmental bacteria are considered as opportunistic pathogens in cystic fibrosis (CF) and are able to persistently colonize the CF respiratory tract (CFRT). Beside Pseudomonas aeruginosa and Burkholderia cepacia complex, Pandoraea spp. are defined as pathogenic. During chronic colonization, adaptive evolution and diversified population have been demonstrated, notably for P. aeruginosa. However, the persistence of Pandoraea in the CFRT remains largely unexplored. We studied genomic and phenotypic traits of Pandoraea pulmonicola isolates successively recovered from the airways of a single CF patient and relate the results to qualitative and quantitative evolution of other cultivable pathogens and to patient clinical status. A total of 31 isolates recovered from 18 sputum samples over a 7-year period in a single CF patient were studied. Genome dynamics was assessed by pulsed-field gel electrophoresis, ERIC-PCR fingerprinting and 16S rRNA gene PCR-temporal temperature gel electrophoresis. Phenotypic features included antimicrobial susceptibility, motility, biofilm production, and virulence in Caenorhabditis elegans model. Variability was observed for all the characteristics studied leading to highly diversified patterns (24 patterns) for the 31 clonally related isolates. Some of these modifications, mainly genomic events were concomitantly observed with CFRT microbiota composition shifts and with severe exacerbations. The diversity of P. pulmonicola population studied, observed for isolates recovered from successive samples but also within a sample suggested that existence of a diversified population may represent a patho-adaptive strategy for host persistence in the heterogeneous and fluctuating CFRT environment

Adaptation and specialization of environmental bacteria to human infection : study of the genus Agrobacterium and Ochrobactrum

Les bactéries pathogènes opportunistes (BPO) sont responsables d'une grande part de la pathologie infectieuse bactérienne. Les BPO d'origine environnementale doivent subir des changements profonds de mode de vie pour s'adapter et coloniser l'homme. Comprendre les conditions de cette adaptation permettra de préciser la notion d'opportunisme infectieux et le rôle des BPO environnementales dans l'émergence des pathogènes.Les genres Ochrobactrum et Agrobacterium regroupent des bactéries présentant une grande variété de modes de vie et établissant différentes relations avec la cellule eucaryote. Ces bactéries connues pour vivre dans l'environnement sont par ailleurs des pathogènes opportunistes de l'homme principalement responsables d'infections chez les individus immunodéprimés. Dans le cadre de ce travail nous avons entrepris une étude populationnelle par une approche de génétique multilocus sur des collections de souches cliniques et environnementales de différentes origines géographiques. Les structures de population obtenues ont été confrontées à divers caractères phénotypiques reliés à la virulence et/ou l'adaptation chez l'homme, la température de croissance, la formation de biofilm et la virulence vis-à-vis des modèles Caenorhabditis elegans et macrophages humains.Ochrobactrum anthropi et Ochrobactrum intermedium sont les deux principales espèces d'intérêt médical du genre Ochrobactrum. La population d'O. anthropi est de type épidémique qui s'organise en deux complexes clonaux (CCs). Si le CC1 regroupe à la fois des souches de diverses origines, le CC4 ne contient que des souches cliniques. Cette sous-population apparait associée à l'homme même si les caractères phénotypiques étudiés ne révèlent pas de différences entre ces deux sous populations. De la même façon, ces deux CCs ne se distinguent pas par leur comportement en modèle macrophage ou par leur diversité génomique. O. intermedium, tout comme O. anthropi, présente une forte diversité génétique toutefois, aucun regroupement des souches en fonction de leur origine n'est mis en évidence pour cette espèce. La diversité des souches cliniques apparait aussi importante que celle de l'ensemble de la population. Plusieurs arguments suggèrent une niche étroite pour cette espèce, notamment une faible diversité génomique. Par ailleurs, le faible nombre de souches environnementales associé à une meilleure croissance planctonique à 37°C qu'à 25°C et 30°C suggèrent que l'homme pourrait constituer cette niche. L'étude de la virulence d'O. intermedium en modèle macrophage ou C. elegans met en évidence différents comportements, pour autant ceux-ci ne semblent pas liés à la structure de population. Certaines souches sont capables de se multiplier dans le modèle macrophage.L'étude du genre Agrobacterium par une approche multilocus sur une collection représentative des différents modes de vie de ces bactéries met en évidence, tout comme pour O. anthropi, une sous population clinique qui regroupe près de 80% des souches de cette origine. D'autres arguments tels que la croissance à 42°C confirment que le génovar A7 peut correspondre à une sous-population associée à l'homme. Les données obtenues seront confrontées aux connaissances sur d'autres bactéries pathogènes opportunistes d'origine environnementale comme Pseudomonas aeruginosa, Stenotrophomonas maltophilia et les bactéries du complexe Burkholderia cepacia qui présentent également des sous populations associées à l'homme et/ou à certaines pathologies humaines. L'existence de ces sous populations suggère une spécialisation qui sera discutée dans le contexte de la spéciation des bactéries pathogènes afin de revisiter le concept d'opportunisme infectieux.The opportunistic bacterial pathogens (OBP) cause the main part of bacterial infectious diseases. Environmental-borne OBP should encounter dramatic changes in lifestyle in order to colonize human beings. The conditions of this adaptation should precise concepts about OBP and emerging pathogens.The genera Ochrobactrum and Agrobacterium groups bacteria with versatile lifestyles that establish diverse relationships with the eukaryotic cells. These environmental-borne OBP caused diverse infectious diseases in immune-compromised patients. In this study, we undertook an approach of multilocus genetic on large population of environmental and clinical strains of Ochrobactrum and Agrobacterium. The population structures were compared to phenotypic traits related to adaptation and virulence in man, such as growth temperature, biofilm formation and virulence tested in Caenorhabditis elegans and human macrophages models.Ochrobactrum anthropi and Ochrobactrum intermedium are the two main Ochrobactrum species to be involved in human diseases. O. anthropi displays an epidemic population structure organized in two large clonal complexes (CCs). CC4 groups only human associated strains whereas CC1 contain environmental and clinical strains. Population genetics suggested that CC4 is a human-associated clone although phenotypic, genomic and virulence traits do not differ between CC1 and CC4 strains.As O. anthropi, O. intermedium displays a high genetic diversity without correlation between the genetic structure and the origin of strains. The level of genetic diversity among clinical strains appears as high as observed in the whole population. Several data such as a low level of genomic diversity suggested that O. intermedium is associated to a narrow ecological niche. The low number of environmental strains described for this species as well as an optimal growth at 37°C suggested that human beings could be the main niche for O. intermedium. Virulence in macrophage and C. elegans models showed diverse behaviour whereas some strains are able to survive and multiply in macrophages model.Multilocus genetics in a population of Agrobacterium spp. that displays diverse lifestyles, revealed a human associated population as observed for O. anthropi. The clinical genovar A7 groups 80% of the clinical strains included in the study, this strains growing at 42°C. Data obtained in this study will be confronted to the knowledge about other environmental-borne OBP such as Pseudomonas aeruginosa, Stenotrophomonas maltophilia and bacteria belonging to the species complex Burkholderia cepacia. All these bacteria displayed sub-populations associated to man or to a particular human disease. These sub-populations suggest a specialization process that will be described in the context of the speciation of bacterial pathogen in order to revisite the concept of « opportunisme infectieux »

A sequence database analysis of 5-nitroimidazole reductase and related proteins to expand knowledge on enzymes responsible for metronidazole inactivation

International audiencenim genes are associated, in combination with other factors, with acquired resistance to metronidazole (MTZ) in anaerobes. These genes encode 5-nitroimidazole reductase enzymes (Nim proteins) that reduce MTZ into an inactive compound. Eleven variants (nimA to nimK) are currently described in anaerobes with either a chromosomal or a plasmidic location. Mostly found in members of the Bacteroides fragilis group, nim genes were demonstrated in anaerobic taxa outside the phylum Bacteroidetes. Nitroreductase enzymes, weakly related to those found in Bacteroidetes but associated with MTZ inactivation, were also characterized both in anaerobic and non-anaerobic taxa. Published data only poorly reflect the growing number of data from cultivation-independent studies and sequences deposited in databases. Considering this limitation, we performed herein an analysis of the sequence databases with the aim to increase the current knowledge on Nim protein distribution and diversity. The 250 sequences the most closely related to the 11 known Nim proteins were selected and analyzed for identity level and phylogenetic relationships with Nim A to K proteins. The analysis revealed a larger diversity of anaerobic species harboring known Nim proteins than that currently described in the literature. Putative new variants of known Nim proteins and novel Nim proteins were found. In addition, nitroreductase proteins and homologs related to the pyridoxamine 5'-phosphate oxidase family were found in highly diverse anaerobic and aerobic taxa of human but also animal and environmental origin. On the other hand, we found a very low number of sequences recovered from metagenomic studies. Considering the different databases currently available to identify antimicrobial resistance genes (ARG) among metagenomic sequences, we hypothesized that this may, at least in part, be related to the incompleteness of ARG databases because none of them includes the 11 described nim genes at the time of our study. Both the wide distribution of proteins with potential MTZ inactivation ability within the bacterial world and a wider diversity of Nim determinants than expected from published literature is underlined in this sequence database analysis

Evaluer le risque d’épidémies nosocomiales par la détection des sous populations environnementales de P. aeruginosa

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Etre pathogènes ou le devenir? une question pour Vibrio cholerae dans les laguneslanguedociennes.

International audienceLa Réunion interdisciplinaire de chimiothérapie antiinfectieuse(RICAI) est, depuis trente quatre ans, le plus important congrès européen de langue française dans le domaine de la thérapeutique antiinfectieuse globale. Elle réunit environ 1500 membres de la communauté de l’infectiologie, chercheurs et cliniciens

Persistence and Dissemination Capacities of a blaNDM-5-Harboring IncX-3 Plasmid in Escherichia coli Isolated from an Urban River in Montpellier, France

International audienceTo investigate the capacities of persistence and dissemination of blaNDM-5 within Escherichiacoli and in aquatic environment, we characterized E. coli (sequence type 636) strains B26 and B28isolated one month apart from the same urban river in Montpellier, France. The two isolates carried apTsB26 plasmid, which sized 45,495 Kb, harbored blaNDM-5 gene and belonged to IncX-3 incompatibilitygroup. pTsB26 was conjugative in vitro at high frequency, it was highly stable after 400 generationsand it exerted no fitness cost on its host. blaNDM-5harboring plasmids are widely dispersed in E. coliall around the world, with no lineage specialization. The genomic comparison between B26 and B28stated that the two isolates probably originated from the same clone, suggesting the persistence ofpTsB26 in an E. coli host in aquatic environment

Dynamique et diversité de Vibrio parahaemolyticus, Vibrio vulnificus et Vibrio cholerae dans la lagune de Biguglia

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