Collagen adhesion gene is associated with blood stream infections caused by methicillin-resistant Staphylococcus aureus

Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) causes hospital- and community-acquired infections. It is not clear whether genetic characteristics of the bacteria contribute to disease pathogenesis in MRSA infection. We hypothesized that whole genome analysis of MRSA strains could reveal the key gene loci and/or the gene mutations that affect clinical manifestations of MRSA infection. Methods: Whole genome sequences (WGS) of MRSA of 154 strains were analyzed with respect to clinical manifestations and data. Further, we evaluated the association between clinical manifestations in MRSA infection and genomic information. Results: WGS revealed gene mutations that correlated with clinical manifestations of MRSA infection. Moreover, 12 mutations were selected as important mutations by Random Forest analysis. Cluster analysis revealed strains associated with a high frequency of bloodstream infection (BSI). Twenty seven out of 34 strains in this cluster caused BSI. These strains were all positive for collagen adhesion gene (cna) and have mutations in the locus, those were selected by Random Forest analysis. Univariate and multivariate analysis revealed that these gene mutations were the predictor for the incidence of BSI. Interestingly, mutant CNA protein showed lower attachment ability to collagen, suggesting that the mutant protein might contribute to the dissemination of bacteria. Conclusions: These findings suggest that the bacterial genotype affects the clinical characteristics of MRSA infection. (c) 2019 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases

Effects of electronic stopping power on fast-ion-induced secondary ion emission from methanol microdroplets

The formation processes of secondary ions in liquid materials were studied for methanol microdroplets bombarded by carbon ions with incident energies of 0.4–4.0 MeV, where the corresponding electronic stopping power ranged 300–800 eV nm−1. Positive and negative secondary ions including molecular fragments, methanol clusters, and reaction products were investigated, and each ion yield was examined as a function of electronic stopping power Se. We observed different Se-dependence on the emission yields between positive and negative ions. For positive cluster ions [(CH3OH)n + H]+ (n = 2−10), the yield nonlinearly increases and follows the power-law Seα with α = 3. For negative secondary ions, the value of α varies according to secondary ion species or ion mass: α ≈ 0 for fragments with small mass (CH−, CH2−, and OH−), α = 0.5–1.5 for reaction products with medium mass(C2−, C2H−, C2HO−, and C2H5O−), and α = 1.2−1.5 for clusters with large mass [(CH3OH)n – H]− (n = 1−25). The latter finding implies that the value of α is a quantity related to the electronic energy density depending on the distance from the ion trajectory

Relation between biomolecular dissociation and energy of secondary electrons generated in liquid water by fast heavy ions

In this work, we measured and simulated the dissociation of biomolecules in liquid water induced by secondary electrons ejected from water molecules during fast heavy-ion irradiation. We calculated the energy spectra of secondary electrons generated along carbon ion tracks in liquid water in the Bragg peak region. The calculation was done using the Particle and Heavy Ion Transport code System (PHITS) in carbon track structure mode. This mode enables simulation of inelastic collisions along a carbon ion track based on the cross sections considered in the Monte Carlo code KURBUC. To understand the biomolecular dissociation processes in our previous MeV-SIMS experiments with microdroplet targets of glycine solution, we calculated the collision spectra of secondary electrons produced near liquid surfaces using PHITS. Furthermore, we examined the relationship between the secondary electron energy and formation of positive and negative glycine fragments. The results showed that the formation of methylene amine cations is caused by secondary electrons with energies of 13–100 eV. The formation of glycine-related negative ions such as cyanide anion, formate anion, and deprotonated glycine was found to be caused by low-energy (less than 13 eV) secondary electrons. These ions are known products of dissociative electron attachment

Time-of-flight imaging in fog using multiple time-gated exposures

We propose a time-of-flight measurement algorithm for depth and intensity that is robust to fog. The key idea of the algorithm is to compensate for the scattering effects of fog by using multiple time-gating and assigning one time-gated exposure for scattering property estimation. Once the property is estimated, the depth and intensity can be reconstructed from the rest of the exposures via a physics-based model. Several experiments with artificial fog show that our method can measure depth and intensity irrespective of the traits of the fog. We also confirm the effectiveness of our method in real fog through an outdoor experiment