Examining the epidemiology and microbiology of Clostridium difficile carriage in elderly patients and residents of a healthcare facility in southern Ontario, Canada.

BACKGROUND: Whereas Clostridium difficile has been extensively studied in acute care facilities (ACFs), there is limited information about long-term care facilities (LTCFs), despite the high occurrence of putative risk factors (e.g. age, antimicrobial use, healthcare system contact). AIM: To evaluate C. difficile colonization in elderly patients and residents from one ACF and its associated LTCF. METHODS: Stool swabs were collected from 884 LTCF and elderly (>65 years) hospital patients. Selective culture, polymerase chain reaction ribotyping and toxin gene characterization were performed. FINDINGS: C. difficile was isolated from 92/410 (22.4%) ACF and 89/474 (18.8%) LTCF samples. Ribotypes 027 (35%) and 020 (10.4%) predominated in the LTCF whereas ribotypes AI-82/1 (20.7%) and ribotype O (14.1%) predominated at the ACF (P = 0.031). In the LTCF, C. difficile colonization was associated with a history of proton pump inhibitor (PPI) use, and the interaction terms of male residents with prior medical leave of absence, and a prior history of C. difficile infection (CDI) combined with fluoroquinolone use. In the ACF, C. difficile colonization was associated with length of stay, feeding through a tube, antibiotic use, immunosuppressive therapy and VRE colonization, as well as the interaction terms for cephalosporin and fluoroquinolone use, prior CDI and cephalosporin use, and prior CDI and fluoroquinolone use. CONCLUSION: C. difficile colonization by ACF and LTCF residents was common, despite a low apparent incidence of CDI. The association with PPI provides further evidence of the potential importance of this widely used drug class in C. difficile colonization. Wide genetic diversity was present, highlighting the likelihood of multiple unidentified routes of C. difficile acquisition.

A quantum mechanical study of water adsorption on the (110) surfaces of rutile SnO2 and TiO2: investigating the effects of intermolecular interactions using hybrid-exchange density functional theory.

Periodic hybrid-exchange density functional theory calculations are used to explore the first layer of water at model oxide surfaces, which is an important step for understanding the photocatalytic reactions involved in solar water splitting. By comparing the structure and properties of SnO2(110) and TiO2(110) surfaces in contact with water, the effects of structural and electronic differences on the water chemistry are examined. The dissociative adsorption mode at low coverage (1/7 ML) up to monolayer coverage (1 ML) on both SnO2 and TiO2(110) surfaces is analysed. To investigate further the intermolecular interactions between adjacent adsorbates, monolayer adsorption on each surface is explored in terms of binding energies and bond lengths. Analysis of the water adsorption geometry and energetics shows that the relative stability of water adsorption on SnO2(110) is governed largely by the strength of the chemisorption and hydrogen bonds at the surface of the adsorbate-substrate system. However on TiO2(110), a more complicated scenario of the first layer of water on its surface arises in which there is an interplay between chemisorption, hydrogen bonding and adsorbate-induced atomic displacements in the surface. Furthermore the projected density of states of each surface in contact with a mixture of adsorbed water molecules and adsorbed hydroxyls is presented and sheds some light on the nature of the crystalline chemical bonds as well as on why adsorbed water has often been reported to be unstable on rutile SnO2(110).

A quantum-mechanical study of the adsorption of prototype dye molecules on rutile-TiO2(110): a comparison between catechol and isonicotinic acid.

In this work we present a theoretical investigation of the attachment of catechol and isonicotinic acid to the rutile-TiO(2)(110) surface. These molecules can be considered as prototypical dyes for use in Grätzel type dye sensitised solar cells (DSCs) and are often employed as anchoring groups in both organic and organo-metallic sensitisers of TiO(2). Our study focuses on determining the lowest energy adsorption mode and discussing the electronic properties of the resultant hybrid interface by means of density functional theory (DFT) calculations using the hybrid exchange (B3LYP) functional. We find that both molecules adsorb dissociatively at the TiO(2) surface giving a type II (staggered) heterojunction. Compared to isonicotinic acid, catechol, due to the greater hybridisation of its molecular orbitals with the states of the substrate, is seen to enhance performance when employed as an anchoring group in dye sensitised solar cells.

He-atom scattering from MgO(100): calculating diffraction peak intensities with a semi ab initio potential.

An efficient model describing the He-atom scattering process is presented. The He-surface interaction potential is calculated from first principles by exploiting second-order Rayleigh-Schrödinger many-body perturbation theory and fitted by using a variety of pairwise interaction potentials. The attractive part of the fitted analytical form has been upscaled to compensate the underestimation of the well depth for this system in the perturbation theory description. The improved potential has been introduced in the close-coupling method to calculate the diffraction pattern. Quantitative agreement between the computed and observed binding energy and diffraction intensities for the He-MgO(100) system is achieved. It is expected that the utility of He scattering for probing dynamical processes at surfaces will be significantly enhanced by this quantitative description.

Periodic quantum mechanical simulation of the He-MgO(100) interaction potential.

He-atom scattering is a well established and valuable tool for investigating surface structure. The correct interpretation of the experimental data requires an accurate description of the He-surface interaction potential. A quantum-mechanical treatment of the interaction potential is presented using the current dominant methodologies for computing ground state energies (Hartree-Fock, local and hybrid-exchange density functional theory) and also a novel post-Hartree-Fock ab initio technique for periodic systems (a local implementation of Mo̸ller-Plesset perturbation theory at second order). The predicted adsorption well depth and long range behavior of the interaction are compared with that deduced from experimental data in order to assess the accuracy of the interaction potential.

Renal safety of CT angiography and perfusion imaging in the emergency evaluation of acute stroke.

BACKGROUND AND PURPOSE: Multimodal CT imaging with contrast-enhanced CT angiography (CTA) and CT perfusion (CTP) is increasingly being used to guide emergency management of acute stroke. However, little has been reported about the safety of intravenous contrast administration associated with these studies in the acute stroke population, including cases in which baseline creatinine values are unknown. We investigated the incidence of contrast-induced nephropathy (CIN), defined as a 25% or more increase in baseline creatinine levels within 72 hours of contrast administration and chronic kidney disease in patients receiving CTA+/-CTP at our regional stroke center. MATERIALS AND METHODS: We analyzed 198 patients who underwent contrast CT studies for evaluation of acute ischemic or hemorrhagic stroke at our center (2003-2007). Through retrospective chart abstraction, we analyzed serial creatinine levels (baseline to day 3) and later values (>/=day 4) where available. The incidences of CIN and/or chronic kidney disease were documented. After power analysis, CIN and non-CIN groups were compared by using the unpaired t test, Wilcoxon rank sum test, or Fisher exact test. RESULTS: None of the 198 patients developed chronic kidney disease or required dialysis. Of 175 patients with serial creatinine measurements between baseline and day 3, 5 (2.9%) developed CIN. The incidence of CIN was 2% in patients who were scanned before a baseline creatinine level was available. CONCLUSION: The incidence of renal sequelae is relatively low in acute stroke patients undergoing emergent multimodal CT scanning. Prompt CTA/CTP imaging of acute stroke, if indicated, need not be delayed in those with no history of renal impairment.

Myocardial protection for cardiac surgery: the nursing perspective.

The advancement of myocardial protection techniques is considered to be the most instrumental in achieving successful cardiac surgical outcomes. Although many issues complicate the efficacy of myocardial protection, warm cardioplegia is instituted more often as a better myocardial protection method for patients undergoing cardiac surgery. Understanding differences in patient response between warm and cold cardioplegia is essential for development of appropriate nursing intervention strategies and prevention of postoperative complications. Advanced practice nurses in cardiac surgical settings must continue to evaluate metabolic, functional, and hemodynamic variations of patients with different cardioplegia for positive patient outcomes.