Increasing the frequency of hand washing by healthcare workers does not lead to commensurate reductions in staphylococcal infection in a hospital ward

Hand hygiene is generally considered to be the most important measure that can be applied to prevent the spread of healthcare-associated infection (HAI). Continuous emphasis on this intervention has lead to the widespread opinion that HAI rates can be greatly reduced by increased hand hygiene compliance alone. However, this assumes that the effectiveness of hand hygiene is not constrained by other factors and that improved compliance in excess of a given level, in itself, will result in a commensurate reduction in the incidence of HAI. However, several researchers have found the law of diminishing returns to apply to hand hygiene, with the greatest benefits occurring in the first 20% or so of compliance, and others have demonstrated that poor cohorting of nursing staff profoundly influences the effectiveness of hand hygiene measures. Collectively, these findings raise intriguing questions about the extent to which increasing compliance alone can further reduce rates of HAI. In order to investigate these issues further, we constructed a deterministic Ross-Macdonald model and applied it to a hypothetical general medical ward. In this model the transmission of staphylococcal infection was assumed to occur after contact with the transiently colonized hands of HCWs, who, in turn, acquire contamination only by touching colonized patients. The aim of the study was to evaluate the impact of imperfect hand cleansing on the transmission of staphylococcal infection and to identify, whether there is a limit, above which further hand hygiene compliance is unlikely to be of benefit. The model demonstrated that if transmission is solely via the hands of HCWs, it should, under most circumstances, be possible to prevent outbreaks of staphylococcal infection from occurring at a hand cleansing frequencies <50%, even with imperfect hand hygiene. The analysis also indicated that the relationship between hand cleansing efficacy and frequency is not linear - as efficacy decreases, so the hand cleansing frequency required to ensure R0<1 increases disproportionately. Although our study confirmed hand hygiene to be an effective control measure, it demonstrated that the law of diminishing returns applies, with the greatest benefit derived from the first 20% or so of compliance. Indeed, our analysis suggests that there is little benefit to be accrued from very high levels of hand cleansing and that in most situations compliance >40% should be enough to prevent outbreaks of staphylococcal infection occurring, if transmission is solely via the hands of HCWs. Furthermore we identified a non-linear relationship between hand cleansing efficacy and frequency, suggesting that it is important to maximise the efficacy of the hand cleansing process

Ribotyping of Pseudomonas aeruginosa Strains Isolated from Surgical Intensive Care Patients

To elucidate the sources of Pseudomonas aeruginosa on a surgical intensive care unit, rDNA restriction fragment length polymorphism analysis (ribotyping) was applied to analyze strains isolated during a 4-month prospective study. Samples included 1635 from 153 patients, 2463 from 97 staff members, and 581 from the environment. Only 18 patients were colonized. Isolation from their animate and inanimate environment was very low, with 3 and 2 samples, respectively, being positive. Samples from tap water were negative. Ribotyping could easily distinguish 16 different digest patterns with identical follow-up isolates of the same patient. Horizontal transmission occurred only twice. The discriminatory power of ribosomal DNA in differentiating strains was dependent on the restriction enzymes used; among eight different enzymes, PvuII was the most sensitive, producing 15 different patterns. Ribotyping showed high sensitivity in typing P. aeruginosa isolates and confirmed that colonization occurs from endogenous rather than from exogenous source

Microwave components based on 2d photonic crystals with unusual index of refraction

This work reports on measurements of microwave components based on Photonic Crystals (PC) with unusual index of refraction, i.e. neff < 1. Particularly lenses based on different PC structures are investigated. All measurements are done in the microwave regime, i.e. for frequencies ranging between 6 and 15 GHz. Intensity gains ranging from 15 to 40, depending on the lens shape and radiation polarization, could be found. Some lens structures focus only in a very narrow wavelength interval, where always a optimum can be find, thus they operate as filters as well. Different kinds of beam splitting could be measured as well. Depending on the lens shape maxima of the beam split occur at different positions and with different intensities. Most of the experimental results will be compared to the ones predicted by theory. A very good agreement between measurements and simulations is evienced

Superlensing with plane plates consisting of dielectric cylinders in glass envelopes

Access full text - https://doi.org/10.1002/pssa.200824209The approach of designing negative-refractive-index materials on the basis of dielectric rods with a gradient of the dielectric constant is tested experimentally. A triangular-lattice plane-parallel slab assembled from multilayer dielectric rods with a refractive index approximating a fish-eye profile is shown to exhibit excellent focusing properties for the TM polarized electromagnetic radiation at frequencies defined by the structural parameters of the slab. A clearly defined super-resolution effect is observed at corresponding frequencies, the width of the focal spot down to a quarter of the wavelength being achieved. The experimental data are partially verified by simulations which show a very good match to the measurements

Efficient Focusing with an Ultra-Low Effective-Index Lens Based on Photonic Crystals

Access full text - https://doi.org/10.1557/PROC-869-D4.4This work focuses on photonic crystals (PC) that can be ascribed an effective index of refraction > 1 or even > 0. We investigate the possibility to design optical elements (in this case a lens) based on this type of PC. A new approach for determining the effective refractive index of PCs with unusual index of refraction is used, which is simpler than earlier methods based on analyzing equi-frequency surfaces in k-space. An ultra-low refractive index PC is given a form approximating a concave lens and is proven theoretically and experimentally that it efficiently focuses the electromagnetic radiation in the microwave range. Strong focusing effects are found for both polarizations (TE and TM mode). Intensity gains as large as 35 for TM polarizations and 29 for TE polarizations are found. Measurements are in a good accordance with simulations

Design and Characterization of Novel Focusing Elements Based on Photonic Metamaterials

Access full text - https://doi.org/10.1166/jno.2009.1003New results in the development of photonic metamaterials based on two dimensional periodic dielectric structures are reported. We show that concave and flat lenses consisting of homogeneous or inhomogeneous dielectric rods can focus electromagnetic waves in spectral regions characterized by effective refractive index neff < 1. In particular, a triangular-lattice photonic crystal—assembled from multilayer dielectric rods designed to approximate a fish-eye profile—is shown to exhibit negative refractive index and good focusing properties at microwave frequencies where the fish-eye dielectric rods scatter the light like a medium with negative refractive index. In some cases the focusing phenomenon proves to be accompanied by super-resolution. The obtained results may be used for the purpose of designing and manufacturing (down scaled) novel micro-lenses for optical integrated circuits

Informe del Comité Científico de la Agencia Española de Seguridad Alimentaria y Nutrición (AESAN) sobre estrategias de identificación de riesgos emergentes alimentarios

Los riesgos emergentes son aquellos derivados de un nuevo peligro para el que puede producirse una exposición significativa, o derivado de una exposición y/o susceptibilidad nueva o incrementada significativamente a un peligro conocido. La identificación de estos riesgos puede realizarse utilizando distintas fuentes de información y herramientas, que pueden ir desde el análisis de bibliografía científica publicada, e incluso de la llamada literatura gris (documentos que no son editados o que se distribuyen a través de canales poco convencionales como tesis doctorales, actas de congresos, informes de investigación, etc.), hasta el estudio de las alertas alimentarias. La evaluación de los riesgos emergentes es realizada por los especialistas en cada área de conocimiento, pero en su identificación pueden utilizarse herramientas comunes a todos ellos de manera que se detecten y caractericen de forma eficaz antes de su evaluación. Por ello, dado que La Ley 17/2011, de Seguridad Alimentaria y Nutrición, establece un mandato para el Comité Científico en relación a la identificación de los riesgos emergentes alimentarios, se solicita a la Sección de Seguridad Alimentaria y Nutrición que elabore un informe sobre las estrategias aplicables para la identificación de riesgos emergentes alimentarios. Teniendo como base la definición de la Autoridad Europea de Seguridad Alimentaria (EFSA) en relación a riesgo emergente es importante identificar si hay un nuevo peligro al que estamos expuestos, o si ha surgido una nueva exposición o se incrementado la exposición a uno conocido. Al mismo tiempo que valorar el incremento de la susceptibilidad a un peligro conocido. Una vez revisadas las distintas estrategias posibles, el Comité Científico considera las siguientes como de utilidad: • Análisis de la bibliografía científica. Para ello es de utilidad el desarrollo o implementación de sistemas potentes de gestión de datos y plataformas de colaboración digital para gestionar la gran cantidad de datos e información disponibles. • Análisis de la literatura gris. Al igual que en el caso anterior se necesitarían herramientas informáticas específicas que permitan extraer información de interés. • Análisis de las alertas y de los resultados de los programas de control oficial. Estas herramientas controlan aquellos riesgos conocidos y sobre los que existe legislación de control. Podrían ser útiles para detectar aumentos de exposición por incrementos en la presencia de algún contaminante a lo largo del tiempo. • Análisis de los sistemas de vigilancia epidemiológica que podrían servir para detectar incrementos de susceptibilidad o exposición. • Análisis de tendencias de consumo. Serviría para detectar incrementos de exposición, siempre que la metodología de recogida de datos sea comparable entre años. • Análisis de la información recabada de estudios de percepción del riesgo por parte de la población. • Análisis de la información procedente de expertos e investigadores. Sería deseable mejorar la colaboración de la comunidad científica con las Instituciones y organizaciones nacionales e internacionales

First molecular identification of the zoonotic parasite Anisakis pegreffii (Nematoda: Anisakidae) in a paraffin-embedded granuloma taken from a case of human intestinal anisakiasis in Italy

<p>Abstract</p> <p>Background</p> <p>Anisakiasis is an important fish-borne zoonosis provoked by larval stages of nematodes belonging to the genus <it>Anisakis</it>. The detection and identification of human infections is difficult. This is due to: a) the low specificity of the clinical features and symptomatology related to human infections; b) the paucity of diagnostic features of larvae found in granulomatous lesions characteristic of "invasive anisakiasis"; and c) the lack morphological characters diagnostic at the specific level when larvae of <it>Anisakis </it>are detected. Thus, molecular-based diagnostic approaches are warranted.</p> <p>Method</p> <p>We have developed a PCR method that amplifies the DNA of <it>Anisakis </it>spp. in fixed paraffin-embedded tissues. This method was applied to a granuloma removed from a human case of intestinal anisakiasis in Italy. Specific primers of the mtDNA <it>cox2 </it>gene were used and sequence analysis was performed according to the procedures already established for species of <it>Anisakis</it>.</p> <p>Results</p> <p>The sequence obtained (629 bp) was compared with those of the other species of <it>Anisakis </it>which have so far been genetically characterized and with sequences obtained from larval stages of <it>Anisakis </it>collected from the Mediterranean fish <it>Engraulis encrasicolus</it>. This enabled the genetic identification of the larva in the human tissue as <it>A. pegreffii</it>. This is the first instance of human intestinal anisakiasis diagnosed using PCR of DNA purified from a fixed eosinophilic granuloma embedded in paraffin.</p> <p>Conclusion</p> <p>The case of human anisakiasis presented reinforces the pathological significance of the species <it>A. pegreffii </it>to humans. The molecular/genetic methodological approach based on mtDNA <it>cox2 </it>sequence analysis, described here, can allow easy and rapid identification of <it>Anisakis </it>spp. in formalin-fixed and paraffin embedded tissues removed from cases of either gastric or intestinal human anisakiasis.</p