18 research outputs found
The phylogenetic landscape and nosocomial spread of the multidrug-resistant opportunist Stenotrophomonas maltophilia
yesRecent studies portend a rising global spread and adaptation of human- or healthcare- associated pathogens. Here, we analyse an international collection of the emerging, multi-drug-resistant, opportunistic pathogen Stenotrophomonas maltophilia from 22 countries to infer population structure and clonality at a global level. We show that the S. maltophilia
complex is divided into 23 monophyletic lineages, most of which harbour strains of all
degrees of human virulence. Lineage Sm6 comprises the highest rate of human-associated
strains, linked to key virulence and resistance genes. Transmission analysis identifies
potential outbreak events of genetically closely related strains isolated within days or weeks
in the same hospitals
2008 Inter-laboratory Comparison Study of a Reference Material for Nutrients in Seawater
Autoclaved natural seawater collected in the North Pacific Ocean was used as a reference material for nutrients in seawater (RMNS) during an inter-laboratory comparison (I/C) study conducted in 2008. This study was a follow-up to previous studies conducted in 2003 and 2006. A set of six samples was distributed to each of 58 laboratories in 15 countries around the globe, and results were returned by 54 of those laboratories (15 countries). The homogeneities of samples used in the 2008 I/C study, based on analyses for three determinants, were improved compared to those of samples used in the 2003 and 2006 I/C studies.
Results of these I/C studies indicate that most of the participating laboratories have an analytical technique for nutrients that is sufficient to provide data of high comparability. The differences between reported concentrations from the same laboratories in the 2006 and 2008 I/C studies for the same batch of RMNS indicate that most of the laboratories have been maintaining internal comparability for two years.
Thus, with the current high level of performance in the participating laboratories, the use of a common reference material and the adaptation of an internationally accepted
nutrient scale system would increase comparability among laboratories worldwide, and
the use of a certified reference material would establish traceability.
In the 2008 I/C study we observed a problem of non-linearity of the instruments of the participating laboratories similar to that observed among the laboratories in the 2006
I/C study. This problem of non-linearity should be investigated and discussed to improve comparability for the full range of nutrient concentrations. For silicate comparability in particular, we see relatively larger consensus standard deviations than those for nitrate and phosphate
Essai de détermination d'une typologie des sédiments cÎtiers en fonction de l'apparition d'eaux colorées
The study of different chemical parameters characterizing the coastal sediment, showed a possible relation between, respectively, high levels in organic matter and total copper, and the "red tide" phenomenon.L'étude de différents paramÚtres caractérisant la composition chimique du sédiment cÎtier, a montré l'existence d'une relation possible entre les teneurs élevées en matiÚre organique totale et en cuivre total, avec le phénomÚne "eaux colorées"
Low occurrence of Pseudomonas aeruginosa in agricultural soils with and without organic amendment
The occurrence of Pseudomonas aeruginosa was monitored at a broad spatial scale in French agricultural soils, from various soil types and under various land uses to evaluate the ability of soil to be a natural habitat for that species. To appreciate the impact of agricultural practices on the potential dispersion of P. aeruginosa, we further investigated the impact of organic amendment at experimental sites in France and Burkina Faso. A real-time quantitative PCR (qPCR) approach was used to analyze a set of 380 samples selected within the French RMQS (âRĂ©seau de Mesures de la QualitĂ© des Solsâ) soil library. In parallel, a culture-dependent approach was tested on a subset of samples. The results showed that P. aeruginosa was very rarely detected suggesting a sporadic presence of this bacterium in soils from France and Burkina Faso, whatever the structural and physico-chemical characteristics or climate. When we analyzed the impact of organic amendment on the prevalence of P. aeruginosa, we found that even if it was detectable in various manures (at levels from 103 to 105 CFU or DNA targets (g drywt)-1 of sample), it was hardly ever detected in the corresponding soils, which raises questions about its survival. The only case reports were from a vineyard soil amended with a compost of mushroom manure in Burgundy, and a few samples from two fields amended with raw urban wastes in the sub-urban area of Ouagadougou, Burkina Faso. In these soils the levels of culturable cells were below 10 CFU (g drywt)-1
Recent Comparability of Oceanographic Nutrients Data: Results of a 2003 Intercomparison Exercise using Reference Materials
An intercomparison exercise was conducted using the recently developed Reference Material for Nutrients in Seawater (RMNS). Discrepancies of reported values among laboratories were greater than the homogeneity of RMNS samples and the reported analytical precision of nutrients. The variability of in-house standards of the participating laboratories might be the most likely source of interlaboratory discrepancies. Therefore, the use of common reference materials, i.e. certified RM, is essential to establish and improve the comparability of nutrient data of the world's oceans
Impact of untreated urban waste on the prevalence and antibiotic resistance profiles of human opportunistic pathogens in agricultural soils from Burkina Faso
Ătude sur la prolifĂ©ration de la micro algue Alexandrium minutum en rade de Brest
Suite Ă lâĂ©vĂ©nement de grande ampleur dâefflorescence dâAlexandrium minutum et des toxicitĂ©s associĂ©es en Rade de Brest en 2012, un projet a Ă©tĂ© Ă©laborĂ© avec la RĂ©gion Bretagne dans le cadre du dĂ©veloppement du port de Brest. LâIfremer a organisĂ© un Ă©chantillonnage dans lâestuaire de la riviĂšre de Daoulas, zone la plus touchĂ©e en 2012, au cours des printemps-Ă©tĂ© 2013 et 2014. Un suivi de la prĂ©sence dâA. minutum dans les sĂ©diments a Ă©galement Ă©tĂ© rĂ©alisĂ© en hiver 2014.
De ces suivis, des mesures réalisées au laboratoire à ce jour, des simulations du modÚle Prévimer ainsi que des résultats du réseau Rephy et Velyger, il ressort que:
* La rade de Brest peut aujourdâhui ĂȘtre considĂ©rĂ©e comme une zone Ă risque pour Alexandrium minutum. En effet, depuis 2012 les blooms sont rĂ©currents, dĂ©passant le seuil dâalerte et entrainant une toxicitĂ© des coquillages. Lâensemble de la rade prĂ©sente des sĂ©diments contaminĂ©s par la prĂ©sence dâA. minutum.
* La pĂ©riode Ă risque sâĂ©tend de mi-mai Ă fin aoĂ»t. Les estuaires du fond de rade, ainsi que le Sillon des Anglais sont les zones les plus touchĂ©es. En Baie de Daoulas et au Sillon des Anglais, lâannĂ©e 2014 a Ă©tĂ© une annĂ©e prĂ©sentant un dĂ©veloppement dâA. minutum, ainsi que des toxicitĂ©s, sur une pĂ©riode trĂšs longue par rapport Ă 2012 et 2013. Le secteur Elorn a vu des concentrations en A. minutum ponctuellement supĂ©rieures au seuil dâalerte mais pas de toxicitĂ©.
* Le suivi Daoulex a mis en Ă©vidence lâimportance de la tempĂ©rature de lâeau pour le dĂ©marrage du bloom. 2014 est une annĂ©e oĂč les tempĂ©ratures de lâeau ont Ă©tĂ© plus chaudes au printemps ce qui coĂŻncide avec un dĂ©marrage beaucoup plus prĂ©coce, dĂšs mi-mai du bloom. CâĂ©tait la situation opposĂ©e en 2013.
* Les apports de nutriments par la riviĂšre Mignonne semblent aussi ĂȘtre un facteur non nĂ©gligeable, 2014 se situant entre les forts dĂ©bits de 2012 et les dĂ©bits plus faibles de 2013. LâintensitĂ© du bloom dâA. minutum prĂ©sente cette mĂȘme diffĂ©rence interannuelle.
* Les blooms dâA. minutum prĂ©sentent des maxima pour les faibles coefficients de marĂ©e, câest-Ă -dire lorsque les courants sont plus faibles et permettent un maintien du bloom dans les fonds dâestuaires, plus favorables Ă la croissance dâA. minutum.
* Lâhydrodynamique de la rade seule ne peut expliquer la distribution dâA. minutum dans lâensemble de la rade Ă partir dâun seul point de germination et de dĂ©veloppement. Il sâagit vraisemblablement de plusieurs foyers de germination et de dĂ©veloppement, qui ensuite vont contaminer, Ă de plus faibles abondances, le reste de la rade.
* Alexandrium minutum nâest quâune espĂšce parmi lâensemble de la communautĂ© microphytoplanctonique mais elle peut devenir dominante au sein de cette communautĂ©, comme en 2012 et 2014.
* Le sĂ©quençage de lâensemble des ARN messagers de souches dâA. minutum a mis en Ă©vidence une diversitĂ© intra-spĂ©cifique extrĂȘmement importante Ă la fois entre souches isolĂ©es au cours dâefflorescences distinctes (Ă la fois dans lâespace et dans le temps), mais Ă©galement au sein dâune mĂȘme efflorescence. Lâimpact de cette diversitĂ© sur la dynamique des efflorescences reste mĂ©connu.
* Une approche de gĂ©nĂ©tique des populations a pu mettre en Ă©vidence des diffĂ©rences de frĂ©quences allĂ©liques entre sites Bretons touchĂ©s par des efflorescences Ă A. minutum. Ceci indique que ces efflorescences se dĂ©veloppent de maniĂšre indĂ©pendante, sans quâil existe de forts flux de gĂšnes entre sites.
* Les populations dâA. minutum de la rade synthĂ©tisent plusieurs types de toxines PSP au cours du bloom.
* Un test bandelette de dĂ©tection et quantification dâA. minutum est en cours de dĂ©veloppement