The housefly Musca domestica as a mechanical vector of Clostridium difficile

Background - Clostridium difficile is a bacterial healthcare-associated infection that may be transferred by houseflies (Musca domestica) due to their close ecological association with humans and cosmopolitan nature. Aim - To determine the ability of M. domestica to transfer C. difficile both mechanically and following ingestion. Methods - M. domestica were exposed to independent suspensions of vegetative cells and spores of C. difficile, then sampled on to selective agar plates immediately postexposure and at 1-h intervals to assess the mechanical transfer of C. difficile. Fly excreta was cultured and alimentary canals were dissected to determine internalization of cells and spores. Findings - M. domestica exposed to vegetative cell suspensions and spore suspensions of C. difficile were able to transfer the bacteria mechanically for up to 4 h upon subsequent contact with surfaces. The greatest numbers of colony-forming units (CFUs) per fly were transferred immediately following exposure (mean CFUs 123.8 +/− 66.9 for vegetative cell suspension and 288.2 +/− 83.2 for spore suspension). After 1 h, this had reduced (21.2 +/− 11.4 for vegetative cell suspension and 19.9 +/− 9 for spores). Mean C. difficile CFUs isolated from the M. domestica alimentary canal was 35 +/− 6.5, and mean C. difficile CFUs per faecal spot was 1.04 +/− 0.58. C. difficile could be recovered from fly excreta for up to 96 h. Conclusion - This study describes the potential for M. domestica to contribute to environmental persistence and spread of C. difficile in hospitals, highlighting flies as realistic vectors of this micro-organism in clinical areas.

Surfactant-mediated variation of band-edge emission in CdS nanocomposites

The optical-structural characteristics of the direct optical band-gap semiconducting series of surfactant template-mediated laminar (CdS)x(CdCl2)y(CnH2n+4N)z nanocomposites are reported. X-ray diffraction measurements of the nanocomposites exhibited interlaminar distances in the range 2.9-3.6 nm with observations of eighth order {0 0 l} diffraction planes indicative of a high degree of laminarity and crystallographic order. Diffuse reflectance measurements have determined that the profile of their emission spectrum is that of a direct band-gap with absorption edges in the range 2.11-2.40 eV, depending on the CdS mole fraction in the nanocomposite. Photoluminescence (PL) excitation and time-resolved PL spectroscopies give an estimate of the maximum relative absorbance of the nanocomposites at ∼420 nm while the minimum was observed at ∼560 nm. The main emission was observed at ∼700 nm with emission from doubly ionized sulphur vacancies observed at ∼615 nm at room temperature. The CdS-containing nanocomposite is thus a surfactant-mediated modular system with variable band-gap energy emission.

Évolution des comportements hyperactifs-impulsifs et inattentifs chez les enfants canadiens âgés de deux à onze ans entre 1994-1995 et 1996-1997

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Chemistry of eastern tropical Atlantic porewater

Distributions of pore water O2, NO-2, NO-3, NH+4, Si(OH)4, PO[3-]4, Mn[2+], F-, and T.A. were determined at 15 stations in the eastern equatorial Atlantic. While overall profile characteristics are consistent with previous models of organic matter diagenesis, profile shapes suggest that a deep reaction layer, rich in organic C, is also present at many sites. While it is unlikely that the oxidation of organic C in this layer has had a major effect on the ocean C cycle, pore water profile shapes are significantly altered. Despite exposure to seawater SO[2-]4 concentrations for > 1000 years, decomposition of the organic matter in the layer appears to be restricted to oxic and suboxic processes. These results suggest major differences in organic carbon decomposition and preservation under oxic/suboxic and anoxic conditions. Present-day benthic fluxes are largest adjacent to the eastern boundary coastal upwelling region and similar in magnitude to values reported for the eastern Pacific. Preliminary estimates suggest that the benthic respiration in the eastern 1/3 of the North Atlantic south of 20°N may alone account for >20% of the total deep North Atlantic respiration. Combining these results with estimates of organic C burial and deep water-column decomposition suggests that this region is a major location of organic C input into the deep sea.

Seasonal variations in surface metabolite composition of Fucus vesiculosus and Fucus serratus sampled at outer Kiel Fjord (August 2012 - July 2013)

The chemical composition of surface associated metabolites of two Fucus species (Fucus vesiculosus and Fucus serratus) was analysed by means of gas chromatography-mass spectrometry (GC-MS) to describe temporal patterns in chemical surface composition. Method: The two perennial brown macroalgae F. vesiculosus and F. serratus were sampled monthly at Bülk, outer Kiel Fjord, Germany (54°27'21 N / 10°11'57 E) over an entire year (August 2012 - July 2013). Per month and species six non-fertile Fucus individuals were collected from mixed stands at a depth of 0.5 m under mid water level. For surface extraction approx. 50 g of the upper 5-10 cm apical thalli tips were cut off per species. The surface extraction of Fucus was performed according to the protocol of de Nys and co-workers (1998) with minor modifications (see Rickert et al. 2015). GC/EI-MS measurements were performed with a Waters GCT premier (Waters, Manchester, UK) coupled to an Agilent 6890N GC equipped with a DB-5 ms 30 m column (0.25 mm internal diameter, 0.25 mM film thickness, Agilent, USA). The inlet temperature was maintained at 250°C and samples were injected in split 10 mode. He carrier gas flow was adjusted to 1 ml min-1. Alkanes were used for referencing of retention times. For further details (GC-MS sample preparation and analysis) see the related publication (Rickert et al. submitted to PLOS ONE).