Accuracy of three automated systems (MicroScan WalkAway, VITEK, and VITEK 2) for susceptibility testing of Pseudomonas aeruginosa against five broad-spectrum beta-lactam agents

One hundred recent clinical Pseudomonas aeruginosa isolates were used to assess the quantitative (MIC) and qualitative (susceptibility category) accuracies of the MicroScan WalkAway, VITEK, and VITEK 2 automated susceptibility test systems when five-broad spectrum beta-lactams, aztreonam, cefepime, ceftazidime, imipenem, and piperacillin-tazobactam, were tested. Isolates were selected so that the MICs for the isolates over-represented the MICs near the breakpoints to assess precisely the agreement between the results obtained with the automated systems and the results obtained by the reference tests. the categorical and MIC results from the automated systems were compared to the consensus result of three reference methods: broth microdilution, agar dilution, and disk diffusion. the consensus categorical testing (susceptibility and resistance) rates were 47 and 27%, respectively, for aztreonam; 59 and 14%, respectively, for cefepime; 44 and 43%, respectively, for ceftazidime; 71 and 19%, respectively, for imipenem; and 50 and 50%, respectively, for piperacillin-tazobactam. All systems tested exhibited a high, unacceptable level of very major (false-susceptible) errors for piperacillin-tazobactam (19 to 27%). Major (false-resistant) error rates were generally acceptable (0 to 3%), but minor error rates were elevated (8 to 32%) for cefepime (VITEK 2 and VITEK) and for aztreonam (all three systems), leading to consistent trends toward false resistance. Manufacturer reevaluation of these automated systems for the testing of selected beta-lactams with current clinical isolates of P. aeruginosa that exhibit contemporary resistance mechanisms would be prudent to minimize the potential for serious reporting errors.JMI Labs Inc, N Liberty, IA 52317 USAUniversidade Federal de São Paulo, Div Infect Dis, São Paulo, BrazilTufts Univ, Sch Med, Boston, MA 02111 USAUniversidade Federal de São Paulo, Div Infect Dis, São Paulo, BrazilWeb of Scienc

Mercury evasion from a boreal peatland determined with advanced REA and chamber methods

Gasförmiges, elementares Quecksilber (Hg^0) ist die dominierende Form von Hg in der Atmosphäre und steht in ständigem Austausch mit Böden und Wasseroberflächen. In borealen Mooren ist dieser Land-Atmosphären-Austausch von Hg^0 von besonderer Relevanz. - in solch anoxischen Ökosystem bildet sich das hochtoxische Methylquecksilber (MeHg) - , da sich verändernde Depositions- und Emissionsraten den Hg-Pool im Boden beeinflussen. Um natürliche influssfaktoren zu bestimmen, welche die Reduktion von Hg(II) zu Hg^0 und damit die Ausgasung fördern, haben wir dynamische Durchflusskammern (DFCs) verwendet. Der Effekt von erhöhter Schwefel- und Stickstoffdeposition sowie veränderten Temperatur- und Feuchtebedingungen auf den Hg^0-Fluss wurden untersucht und typische Flussraten für unser Untersuchungsgebiet quantifiziert. Das boreale Moor liegt etwa 10 Kilometer westlich von Vindeln, in der Provinz Västerbotten in Schweden. Um den ganzjährigen In- und Output von Hg^0 über die Atmosphäre zu quantifizieren, entwickelten wir ein neues Relaxed Eddy Accumulation (REA) System mit zwei Lufteinlässen, nur einem Detektor und einem ausgefeilten, automatischen Kalibrationsmodul. Während den Hg-Messungen wurden meteorologische Parameter, im Wasser gelöstes Hg^0(DGM) und die Gesamtdeposition von Hg gemessen. Letztere während der Vegetationsperiode 2014. Das Gesamt-Hg im Boden und im Abflussbereich des Moores wurde vorgängig bestimmt und trägt zum besseren Verständnis des Hg-Kreislaufs bei. Hohe Schwefeldepositionen, wie sie in den 80er-Jahren in Schweden üblich waren, führten zu einer Hemmung von Hg-Emissionen. Dies ist mit einer initialen Ausgasung von Hg zu Beginn des Versuches oder mit dem Binden von Hg an Schwefelgruppen und anschliessendem Abtransport im Oberflächenwasser zu erklären. DFC-Messungen im Juli 2014 wurden während Strahlungstagen durchgeführt und zeigten einen deutlichen Tagesgang und eine starke lineare Abhängigkeit von der Temperatur innerhalb und ausserhalb der Kammern. Erste Auswertungen der REA-Daten zeigten eine Spannweite der Monatsmittelwerte zwischen -6 ng m^-2 h^-1 im November 2013 und 15 ng m^-2 h^-1 im Juni 2014. Hg^0-Emissionen dominierten während des Sommers und Hg^0-Deposition von Spätherbst bis Frühling. Als erste Forschungsgruppe gelang es uns, den Hg^0-Fluss über einem borealen Moor während eines ganzen Jahres zu messen und dabei REA erfolgreich anzuwenden. Des Weiteren konnten wir mit DFC-Messungen Faktoren identifizieren, welche Hg^0-Emissionen hemmen oder begünstigen. Die Ausgasung von Hg^0 in die Atmosphäre scheint die Menge im Abfluss deutlich zu übersteigen und deutet darauf hin, dass das boreale Moor heute nicht nur eine Quelle für MeHg, sondern auch für Gesamt-Hg ist

Effects of RAF inhibitors on PI3K/AKT signalling depend on mutational status of the RAS/RAF signalling axis

Targeted therapies within the RAS/RAF/MEK/ERK signalling axis become increasingly popular, yet cross-talk and feedbacks in the signalling network lead to unexpected effects. Here we look systematically into how inhibiting RAF and MEK with clinically relevant inhibitors result in changes in PI3K/AKT activation. We measure the signalling response using a bead-based ELISA, and use a panel of three cell lines, and isogenic cell lines that express mutant forms of the oncogenes KRAS and BRAF to interrogate the effects of the MEK and RAF inhibitors on signalling. We find that treatment with the RAF inhibitors have opposing effects on AKT phosphorylation depending on the mutational status of two important oncogenes, KRAS and BRAF. If these two genes are in wildtype configuration, RAF inhibitors reduce AKT phosphorylation. In contrast, if BRAF or KRAS are mutant, RAF inhibitors will leave AKT phosphorylation unaffected or lead to an increase of AKT phosphorylation. Down-regulation of phospho-AKT by RAF inhibitors also extends to downstream transcription factors, and correlates with apoptosis induction. Our results show that oncogenes rewire signalling such that targeted therapies can have opposing effects on parallel pathways, which depend on the mutational status of the cell

Comparative study of elemental mercury flux measurement techniques over a Fennoscandian boreal peatland

Quantitative estimates of the land-atmosphere exchange of gaseous elemental mercury (GEM) are biased by the measurement technique employed, because no standard method or scale in space and time are agreed upon. Here we present concurrent GEM exchange measurements over a boreal peatland using a novel relaxed eddy accumulation (REA) system, a rectangular Teflon (R) dynamic flux chamber (DFC) and a DFC designed according to aerodynamic considerations (Aero-DFC). During four consecutive days the DFCs were placed alternately on two measurement plots in every cardinal direction around the REA sampling mast. Spatial heterogeneity in peat surface characteristics (0-34 cm) was identified by measuring total mercury in eight peat cores (57 +/- 8 ng g(-1), average SE), vascular plant coverage (32-52%), water table level (4.5-14.1 cm) and dissolved gaseous elemental mercury concentrations (28-51 pg L-1) in the peat water. The GEM fluxes measured by the DFCs showed a distinct diel pattern, but no spatial difference in the average fluxes was detected (ANOVA, alpha = 0.05). Even though the correlation between the Teflon DFC and Aero-DFC was significant (r = 0.76, p < 0.05) the cumulative flux of the Aero-DFC was a factor of three larger. The average flux of the Aero-DFC (1.9 ng m(-2) h(-1)) and REA (2 ng m(-2) h(-1)) were in good agreement. The results indicate that the novel REA design is in agreement for cumulative flux estimates with the Aero-DFC, which incorporates the effect of atmospheric turbulence. The comparison was performed over a fetch with spatially rather homogenous GEM flux dynamics under fairly consistent weather conditions, minimizing the effect of weather influence on the data from the three measurement systems. However, in complex biomes with heterogeneous surface characteristics where there can be large spatial variability in GEM gas exchange, the small footprint of chambers ( < 0.2 m(2)) makes for large coefficients of variation. Thus many chamber measurement replications are needed to establish a credible biome GEM flux estimate, even for a single point in time. Dynamic flux chambers will, however, be able to resolve systematic differences between small scale features, such as experimentally manipulated plots or small scale spatial heterogeneity

Valor genético de genitores de batata para capacidade de hibridação.

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