Detection of Escherichia coli sequence type 131 by matrix-assisted laser desorption ionization time-of-flight mass spectrometry: implications for infection control policies?

International audienceSequence type 131 (ST131) is a predominant lineage among extraintestinal pathogenic Escherichia coli. It plays a major role in the worldwide dissemination of extended-spectrum β-lactamase (ESBL)-producing E. coli. The ST131 pandemic is mainly the result of clonal expansion of the single well-adapted subclone H30-Rx, which is acquired in hospitals more frequently than other ESBL-producing E. coli clones. To develop a rapid method using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) to identify ST131 for infection control purposes. Peak biomarkers of ST131 were identified from the mass spectrum profiles of 109 E. coli isolates (including 50 ST131 isolates). The models accurately identified ST131 isolates from mass spectrum profiles obtained with and without protein extraction. The rapid identification of ST131 isolates with MALDI-TOF MS can be easily implemented in the laboratory, and could help to target infection control measures in patients carrying multi-drug-resistant E. coli that are more likely to spread

AnaEE-France research infrastructure services for experimental studies on soil biodiversity and associated ecological functions

AnaEE-France research infrastructure services for experimental studies on soil biodiversity and associated ecological functions. 1. Global Soil Biodiversity Conference : Assessing Soil Biodiversity and its Role for Ecosystem Service

Integration of hydraulic and chemical signalling in the control of stomatal conductance and water status of droughted plants.

We describe here an integration of hydraulic and chemical signals which control stomatal conductance of plants in drying soil, and suggest that such a system is more likely than control based on chemical signals or water relations alone. The determination of xylem [ABA] and the stomatal response to xylem [ABA] are likely to involve the water flux through the plant. (1) If, as seems likely, the production of a chemical message depends on the root water status (Ψr), it will not depend solely on the soil water potential (Ψs) but also on the flux of water through the soil-plant-atmosphere continuum, to which are linked the difference between Ψr and Ψs. (2) The water flux will also dilute the concentration of the message in the xylem sap. (3) The stomatal sensitivity to the message is increased as leaf water potential falls. Stomatal conductance, which controls the water flux, therefore would be controlled by a water-flux-dependent message, with a water-flux-dependent sensitivity. In such a system, we have to consider a common regulation for stomatal conductance, leaf and root water potentials, water flux and concentration of ABA in the xylem. In order to test this possibility, we have combined equations which describe the generation and effects of chemical signals and classical equations of water flux. When the simulation was run for a variety of conditions, the solution suggested that such common regulation can operate. Simulations suggest that, as well as providing control of stomatal conductance, integration of chemical and hydraulic signalling may also provide a control of leaf water potential and of xylem [ABA], features which are apparent from our experimental data. We conclude that the root message would provide the plant with a means to sense the conditions of water extraction (soil water status and resisance to water flux) on a daily timescale, while the short-term plant response to this message would depend on the evaporative demand