Zn speciation in the organic horizon of a contaminated soil by micro X-ray fluorescence, micro and powder EXAFS spectroscopy and isotopic dilution.

Soils which have been acutely contaminated by heavy-metals show distinct characteristics, such as colonization by metal-tolerant plant species and topsoil enrichment in weakly degraded plant debris because biodegradation processes are strongly inhibited by contamination. Such an organic topsoil, located downwind of an active zinc smelter and extremely rich in Zn (~ 2%, dry weight), was investigated by X-ray diffraction (XRD), synchrotron-based X-ray microfluorescence (μSXRF), and powder and micro extended X-ray absorption fine structure (EXAFS) spectroscopy for Zn speciation, and by isotopic dilution for Zn lability. EXAFS spectra recorded on size fractions and on selected spots of thin sections were analyzed by principal component analysis (PCA) and linear combination fits (LCFs). Although Zn primary minerals (franklinite, sphalerite and willemite) are still present (~ 15% of total Zn) in the bulk soil, Zn was found to be predominantly speciated as Zn-organic matter complexes (~ 45%), outer-sphere complexes (~ 20%), Zn-sorbed phosphate (~ 10%) and Znsorbed iron oxyhydroxides (~ 10%). The bioaccumulated Zn fraction is likely complexed to soil organic matter after the plants' death. The proportion of labile Zn ranges from 54 to 92%, depending on the soil fraction, in agreement with the high proportion of organically-bound Zn. Despite its marked lability, Zn seems to be retained in the topsoil thanks to the huge content of organic matter, which confers to this horizon a high sorption capacity. The speciation of Zn in this organic soil horizon is compared with that found in other types of soils

Multinational prospective cohort study of rates and risk factors for ventilator-associated pneumonia over 24 years in 42 countries of Asia, Africa, Eastern Europe, Latin America, and the Middle East: Findings of the International Nosocomial Infection Control Consortium (INICC)

Objective: Rates of ventilator-associated pneumonia (VAP) in low- and middle-income countries (LMIC) are several times above those of high-income countries. The objective of this study was to identify risk factors (RFs) for VAP cases in ICUs of LMICs. Design: Prospective cohort study. Setting: This study was conducted across 743 ICUs of 282 hospitals in 144 cities in 42 Asian, African, European, Latin American, and Middle Eastern countries. Participants: The study included patients admitted to ICUs across 24 years. Results: In total, 289,643 patients were followed during 1,951,405 patient days and acquired 8,236 VAPs. We analyzed 10 independent variables. Multiple logistic regression identified the following independent VAP RFs: male sex (adjusted odds ratio [aOR], 1.22; 95% confidence interval [CI], 1.16-1.28; P <.0001); longer length of stay (LOS), which increased the risk 7% per day (aOR, 1.07; 95% CI, 1.07-1.08; P <.0001); mechanical ventilation (MV) utilization ratio (aOR, 1.27; 95% CI, 1.23-1.31; P <.0001); continuous positive airway pressure (CPAP), which was associated with the highest risk (aOR, 13.38; 95% CI, 11.57-15.48; P <.0001)Revisión por pare

A test of Garicano's knowledge model

Garicano's model has become one of the main models dealing with the analysis of the structure of information within organizations. It is used in many fields such as labor economics, international economics and strategic management. However, few papers have attempted to test the predictions of this model at the microeconomic level. In this paper we provide a test of two predictions of Garicano's model, using a French matched employer-employee database

Disentangling the roles of demographic and temporal trends in musculoskeletal disorders

International audienc

Detection and enumeration of Pseudomonas aeruginosa in soil and manure assessed by an ecfX qPCR assay

International audienceAimsTo develop a qPCR approach for the detection of Pseudomonas aeruginosa in soil and manure and explore its efficacy and limitations compared with that of a classical culture-dependent approach.Methods and ResultsA Ps. aeruginosa ecfX qPCR assay was developed. This assay was optimized for soils of contrasting physico-chemical properties and evidenced a three-log dynamic range of detection [5 × 104 – 5 × 106 cells (g drywt soil)−1] in inoculated microcosms. Sensitivity was determined to be around 5 × 104 cells (g drywt soil)−1. In parallel, the minimum detection limit was estimated in the range of 10–100 CFU (g drywt soil)−1 using a culture-dependent approach based on the use of a selective medium (cetrimide agar base medium supplemented with nalidixic acid), coupled to ecfX gene amplification to confirm isolate identity. These soil samples led to the growth of abundant non-Ps. aeruginosa colonies mainly belonging to other Pseudomonas species but also some beta-Proteobacteria. These bacteria strongly impacted the detection threshold of this approach. Efficacy of these approaches was compared for Ps. aeruginosa enumeration among manure and agricultural soil samples from various sites in France, Tunisia and Burkina Faso.ConclusionsThe developed qPCR assay enabled a specific detection of Ps. aeruginosa in soil and manure samples. The culture-based approach was usually found more sensitive than the qPCR assay. However, abundance of non-Ps. aeruginosa species among the indigenous communities able to grow on the selective medium affected the sensitivity of this latter approach.Significance and Impact of the StudyThis study describes the first specific and sensitive qPCR assay for the detection and enumeration of Ps. aeruginosa in soil and manure and shows its complementarity with a culture-based approach

Soils as reservoir of opportunistic human material pathogens and impact of agricultural practices

National audienc