Combined use of bacteriophage K and a novel bacteriophage to reduce Staphylococcus aureus biofilm formation

Biofilms are major causes of impairment of wound healing and patient morbidity. One of the most common and aggressive wound pathogens is Staphylococcus aureus, displaying a large repertoire of virulence factors and commonly reduced susceptibility to antibiotics, such as the spread of methicillin-resistant S. aureus (MRSA). Bacteriophages are obligate parasites of bacteria. They multiply intracellularly and lyse their bacterial host, releasing their progeny. We isolated a novel phage, DRA88, which has a broad host range among S. aureus bacteria. Morphologically, the phage belongs to the Myoviridae family and comprises a large double-stranded DNA (dsDNA) genome of 141,907 bp. DRA88 was mixed with phage K to produce a high-titer mixture that showed strong lytic activity against a wide range of S. aureus isolates, including representatives of the major international MRSA clones and coagulase-negative Staphylococcus. Its efficacy was assessed both in planktonic cultures and when treating established biofilms produced by three different biofilm-producing S. aureus isolates. A significant reduction of biofilm biomass over 48 h of treatment was recorded in all cases. The phage mixture may form the basis of an effective treatment for infections caused by S. aureus biofilms

Microphysics and energy and water fluxes of various fog types at SIRTA, France

During the PARISFOG campaign in winter 2012/2013, microphysical properties and turbulent fluxes of fog droplets (liquid water), water vapor, and energy were characterized and quantified during fog events of various types that occurred at the SIRTA (Site Instrumental de Recherche par Teledetection Atmospherique) atmospheric observatory outside Paris. The eddy covariance technique was applied, employing a fast (10 Hz) fog droplet spectrometer, a three-dimensional ultrasonic anemometer, and a fast response gas analyzer, which were operated at an altitude of 2.5 m above ground. A visibility-meter was used to detect the occurrence and density of fog. A total of twenty-one fog events were measured during the field campaign. After applying quality criteria, six events remained. For this study, two fog events out of the six, representing a radiation fog and stratus lowering fog, respectively, are analyzed in detail. The two fog events exhibited very distinct patterns in terms of fog droplet size distribution, fog number concentration, and liquid water content. The evolution of these microphysical properties is elucidated through combined analysis of the turbulent fluxes of fog droplets (liquid water), water vapor and energy as well as reasoning of microphysical processes like, condensation, collision-coalescence, and droplet evaporation. Downward droplet number fluxes and liquid water fluxes were mostly observed in stratus lowering fog, however, upward fluxes were also observed in response to downward water vapor fluxes. In radiation fog, both upward and downward droplet number fluxes and liquid water fluxes were observed depending on the position at which the microphysical process was observed with respect to the measurement height. Bi-directional fog droplet fluxes with different flux directions of smaller and larger droplets were observed. In both fog events, the downward water vapor fluxes were the major cause for (I) the broadening of the fog droplet size distribution and (II) the largest upward fog water fluxes throughout the whole event. (C) 2014 Elsevier B.V. All rights reserved

Fog chemical composition and its feedback to fog water fluxes, water vapor fluxes, and microphysical evolution of two events near Paris

The chemical composition of collected fog water and its temporal evolution was studied during the PARISFOG campaign in winter 2012/2013 at the SIRTA (Site Instrumental de Recherche par Teledetection Atmospheric) atmospheric observatory outside Paris, France. A further development of the caltech active fog collector was applied, in which the collected fog water gets into contact with Teflon and polyether ether ketone (PEEK) material exclusively. The collector was operational whenever the visibility was below 1000 m. In addition, the turbulent and gravitational fluxes of fog water and water vapor flux were used to examine in detail the temporal evolution the chemical composition of two fogs. The technique was applied to two fog events, one representing a radiation fog and the other one representing a stratus lowering fog. The result revealed that the dominant inorganic species in the fog water were NH4+, NO3-, Ca2+ and SO42-, which accounted for more than 85% of the ion balance. The pH ranged from 3.7 to 6.2. In the evolution the two fog events, the interaction among the turbulent fog water flux, gravitational fog water flux and water vapor flux controlled the major ion loads (amount of ions, dissolved in fog droplets per volume of air) and ion concentrations (amount dissolved per volume of liquid water) of the fog water. In the radiation fog event, an increase of ion loads and ion concentrations occurred when the direction of water vapor flux towards to the place where the condensation process occurred. A decrease of ion loads and ion concentrations mainly happened by gravitational fog water flux with a minor contribution from turbulent fog water flux. However, when the turbulent water vapor flux was oriented downward, it turned the turbulent fog water flux upward and offset the removal of ions in the fog. In the stratus lowering fog event, the turbulent fog water flux and the gravitational water flux together mainly contributed to the fog water deposition and removal of ions. Increases of ion loads and ion concentrations occurred in response to slight downward water vapor flux. This study also indicates that the turbulent transport of fog droplets contributed to the preferential deposition of certain sizes fog droplets such that it affected the chemical composition of the fog water. For instance, both the NO3- concentration and load decreased fast as compared to NH4+ and SO42- during the deposition period. This suggested that the chemical composition was dependent on fog droplets size. (C) 2015 Elsevier B.V. All rights reserved