Efflux-mediated fluoroquinolone resistance in the multidrug-resistant Pseudomonas aeruginosa clinical isolate PA7: identification of a novel MexS variant involved in upregulation of the mexEF-oprN multidrug efflux operon

The emergence of multidrug-resistant Pseudomonas aeruginosa has become a serious problem in medical settings. P. aeruginosa clinical isolate PA7 is resistant to fluoroquinolones, aminoglycosides, and most -lactams but not imipenem. In this study, enhanced efflux-mediated fluoroquinolone resistance of PA7 was shown to reflect increased expression of two resistance nodulation cell division (RND) -type multidrug efflux operons, mexEF-oprN and mexXY-oprA. Such a clinical isolate has rarely been reported because MexEF-OprN-overproducing mutants often increase susceptibility to aminoglycosides apparently owing to impairment of the MexXY system. A mutant of PA7 lacking three RND-type multidrug efflux operons (mexAB-oprM, mexEF-oprN, and mexXY-oprA) was susceptible to all anti-pseudomonas agents we tested, supporting an idea that these RND-type multidrug efflux transporters are molecular targets to overcome multidrug resistance in P. aeruginosa. mexEF-oprN-upregulation in P. aeruginosa PA7 was shown due to a MexS variant harboring the Valine-155 amino acid residue. This is the first genetic evidence shown that a MexS variant causes mexEF-oprN-upregulation in P. aeruginosa clinical isolates

New Method of Avoiding Underestimation of Caries Incidence and Its Association with Possible Risk Factors in Japanese University Students: A Prospective Cohort Study

The objective of this three-year prospective cohort study was to investigate the association between a new definition of an increase in dental caries and risk factors in Japanese young adults. Data of Okayama University students who volunteered to undergo oral examinations and answer questionnaires in 2015 and 2018 were analyzed. The status of filled teeth and the status of occlusal/proximal surfaces of filled or decayed teeth were recorded. An increase in dental caries was defined as a change in the status of filled teeth and/or an increase in dental caries of occlusal and proximal surfaces. A total of 393 participants (18.2 +/- 0.8 years) were analyzed. First and second molars showed a high prevalence of dental caries. Of the participants, 144 (36.6%) showed an increase in dental caries. In all the participants and in the females, the decayed, missing, and filled teeth (DMFT) score and history of orthodontic treatment at baseline were significantly associated with an increase in dental caries (p = 2) at baseline were significantly associated with an increase in dental caries (p = 0.04). The DMFT score and history of orthodontic treatment at baseline can be risk factors for an increase in dental caries using the new definition in young adults

Pt atoms adsorbed on TiO2(110)-(1 × 1) studied with noncontact atomic force microscopy and first-principles simulations

We have studied the local properties of single Pt atoms adsorbed on hydroxylated TiO2(110)-(1 × 1) by combining noncontact atomic force microscopy (nc-AFM) and first-principles calculations. Room-temperature high-resolution nc-AFM images for the most frequently observed contrast modes reveal bright and elongated protrusions that can be traced back to the Pt atoms, and that are centered on the fivefold coordinated titanium rows, confined between two bridging oxygen rows. These observations are in line with the theoretical results, as the lowest energy sites for the Pt atom on the TiO2(110) surface are in the neighborhood of the titanium rows, and high energy barriers have to be overcome to displace the Pt atom over the bridging oxygen rows. Single Pt atoms can be distinguished from H adsorbates (OH defects) due to their characteristic shape and binding site and, because they appear as the brightest surface features in all of the contrast modes. Force spectroscopy data over the protrusion and hole imaging modes and the corresponding tip-sample forces, simulated with O and OH terminated TiO2 nanoclusters, provide an explanation for this puzzling result in terms of the intrinsic strength of the interaction with the Pt adatom and the adatom and tip apex relaxations induced by the tip-sample interaction. These imaging mechanisms can be extended to other electropositive metal dopants and support the use of nc-AFM not only to characterize their adsorption structure but also to directly probe their chemical reactivityThis work was supported by Grants-in-Aid for Scientific Research (No. 22221006, No. 25106002, No. 24360016, No. 26600099, No. 2600015, No. 26110516, and No. 20760024) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, Funding Program for Next Generation World-Leading Researchers and by the Ministerio de Economia y Competitividad (MINECO, Spain) uder Projects No. MAT2011-23627, No. CSD2010-00024, and No. PLE2009-006

Quantum degeneracy in atomic point contacts revealed by chemical force and conductance

Quantum degeneracy is an important concept in quantum mechanics with large implications to many processes in condensed matter. Here, we show the consequences of electron energy level degeneracy on the conductance and the chemical force between two bodies at the atomic scale. We propose a novel way in which a scanning probe microscope can detect the presence of degenerate states in atomic-sized contacts even at room temperature. The tunneling conductance G and chemical binding force F between two bodies both tend to decay exponentially with distance in a certain distance range, usually maintaining direct proportionality G∝F. However, we show that a square relation G∝F2 arises as a consequence of quantum degeneracy between the interacting frontier states of the scanning tip and a surface atom. We demonstrate this phenomenon on the Si(111)-(7×7) surface reconstruction where the Si adatom possesses a strongly localized dangling-bond state at the Fermi levelThis work was supported by Grants-in-Aid for Scientific Research (Grants No. 22221006, No. 24360016, No. 24651116, No. 22760028, and No. 25106002) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT), Funding Program for Next Generation World-Leading Researchers. P. J. and M. O. acknowledge the financial support of GAAV M100101207. M.O. acknowledges the support provided by the Czech Science Foundation (GAČR) under Project No. P204/11/P578. R. P. and P. P. acknowledge Projects No. MAT2011-23627, No. CSD2010-00024, No. PLE2009-0061 (MINECO, Spain), and CAM S2009/ MAT-1467. P. P. was supported by the Ramón y Cajal Program (MINECO, Spain

モノアザテトラチオエーテルを含有する温度感応性高分子による銀(I)イオンの抽出挙動

A novel temperature sensitive extraction copolymers, 9-aza-3,6,12,15-tetrathiaheptadecane-derivatized N-isopropylacrylamide polymer (ATH-NIPAAm), has been synthesized in various incorporation ratios. The concentration of monoaza-tetrathioether groups in the copolymers was determined by ICP-AES measurements. The temperature-elevated extraction experiments revealed that Silver (I) ion was extracted efficiently into the polymer phase above the lower critical solution temperature (LCST). As the ratio of monoaza-tetrathioether groups in the polymer increased, the extraction efficiency of silver (I) ion was increased

Understanding image contrast formation in TiO 2 with force spectroscopy

Site-specific force measurements on a rutile TiO 2(110) surface are combined with first-principles calculations in order to clarify the origin of the force contrast and to characterize the tip structures responsible for the two most common imaging modes. Our force data, collected over a broad range of distances, are only consistent with a tip apex contaminated with clusters of surface material. A flexible model tip terminated with an oxygen explains the protrusion mode. For the hole mode we rule out previously proposed Ti-terminated tips, pointing instead to a chemically inert, OH-terminated apex. These two tips, just differing in the terminal H, provide a natural explanation for the frequent contrast changes found in the experiments. As tip-sample contact is difficult to avoid while imaging oxide surfaces, we expect our tip models to be relevant to interpret scanning probe studies of defects and adsorbates on TiO 2 and other technologically relevant metal oxidesWe thank the MEXT (19053006, 22221006, 21246010, 21656013, 20760024, and 22760028), JST, Handai FRC (Japan), and the spanish MICINN (MAT2008-1497, CSD2007-41, MAT2008-02929, MAT2008-02939-E, MAT2008-02953-E, PLE2009-0061, CSD2010-00024) for financial support. P.J. thanks ME10076. Y.S., C.G., and P.P. thank, respectively, Funding Program for Next Generation World-Leading Researchers, a CSIC JAE-Doc contract, and the Ramon y Cajal Program (MICINN