Invasive bacterial infections following influenza: a time-series analysis in Montréal, Canada, 1996-2008.

BACKGROUND: Shared seasonal patterns, such as between influenza and some respiratory bacterial infections, can create associations between phenomena not causally related. OBJECTIVES: To estimate the association of influenza with subsequent bacterial infections after full adjustment for confounding by seasonal and long-term trends. METHODS: Time series of weekly counts of notified cases of invasive infections with Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae and Streptococcus pyogenes, in Montréal, Canada, 1996-2008, were modelled by negative binomial regression, with terms representing seasonal and long-term trends and terms for numbers of positive laboratory tests for influenza A and B. RESULTS: The associations of S. pneumoniae, H. influenzae and N. meningitidis with influenza disappeared after seasonal terms were added to the model. However, the influenza B count remained associated with the S. pyogenes counts for the same week and the following week: S. pyogenes incidence rate ratios were 1.0376 (95% CI: 1.0009-1.0757) and 1.0354 (0.9958-1.0766), respectively, for each increase of 1 in the influenza count. CONCLUSIONS: Influenza B accounts for about 8 percnt; of the incidence of invasive S. pyogenes infections, over and above any effect associated with modellable seasonal and long-term trends. This association of influenza B with S. pyogenes infections can be attributed largely to the years 1997, 2001, 2007 and 2008, when late peaks in influenza B counts were followed by peaks in S. pyogenes notifications. This finding reinforces the case for universal immunization against influenza, as partial protection against the 'flesh eating disease'.

Quantitative statistical analysis, optimization and noise reduction of atomic resolved electron energy loss spectrum images.

In this work we investigate methods of statistical processing and background fitting of atomic resolution electron energy loss spectrum image (SI) data. Application of principal component analysis to SI data has been analyzed in terms of the spectral signal-to-noise ratio (SNR) and was found to improve both the spectral SNR and its standard deviation over the SI, though only the latter was found to improve significantly and consistently across all data sets analyzed. The influence of the number of principal components used in the reconstructed data set on the SNR and resultant elemental maps has been analyzed and the experimental results are compared to theoretical calculations.

Seroprevalence of seven zoonotic infections in Nunavik, Quebec (Canada).

In Nunavik, common practices and food habits such as consumption of raw meat and untreated water place the Inuit at risk for contracting zoonotic diseases. The aim of this study was to determine the seroprevalence of seven zoonotic infections among the permanent residents of Nunavik. The study was conducted in the fall 2004 as part of the Nunavik Health Survey. Blood samples from adults aged 18-74 years (n = 917) were collected and analysed for the presence of antibodies against Trichinella spp., Toxocara canis, Echinococcus granulosus, Brucella spp., Coxiella burnetii, Leptospira spp. and Francisella tularensis. Information on sociodemographic characteristics, traditional activities, drinking water supply and nutrition was gathered using english/inuktitut bilingual questionnaires. The chi-squared test was used to evaluate associations between seropositivity and other measured variables. Statistically significant variables were included in a multivariate logistic regression model to control for confounding factors. Estimated seroprevalences were 8.3% for E. granulosus, 3.9% for T. canis, 5.9% for Leptospira spp. and 18.9% for F. tularensis. Seroprevalence was ≤ 1% for Trichinella spiralis, Brucella spp. and C. burnetii. For most infections, seropositivity tended to increase with age. In multivariate analyses, seroprevalence was positively (i.e. directly) associated with age and residence in the Ungava coast area for F. tularensis; age and residence in the Hudson coast area for T. canis; female gender, lower level of schooling and frequent cleaning of water reservoirs for E. granulosus. No risk factor for Leptospira spp. infection was identified. No associations were detected with regards to food habits or environmental exposures. A small but significant portion of the Nunavik population has serologic evidence of exposure to at least one of the pathogenic microorganisms investigated. Further studies are needed to better understand the mechanisms for transmission of zoonotic infections and their potential reservoirs in Nunavik.

p-Type modulation doped InGaN/GaN dot-in-a-wire white-light-emitting diodes monolithically grown on Si(111).

Full-color, catalyst-free InGaN/GaN dot-in-a-wire light-emitting diodes (LEDs) were monolithically grown on Si(111) by molecular beam epitaxy, with the emission characteristics controlled by the dot properties in a single epitaxial growth step. With the use of p-type modulation doping in the dot-in-a-wire heterostructures, we have demonstrated the most efficient phosphor-free white LEDs ever reported, which exhibit an internal quantum efficiency of ∼56.8%, nearly unaltered CIE chromaticity coordinates with increasing injection current, and virtually zero efficiency droop at current densities up to ∼640 A/cm(2). The remarkable performance is attributed to the superior three-dimensional carrier confinement provided by the electronically coupled dot-in-a-wire heterostructures, the nearly defect- and strain-free GaN nanowires, and the significantly enhanced hole transport due to the p-type modulation doping.

Multipolar plasmonic resonances in silver nanowire antennas imaged with a subnanometer electron probe.

We detect short-range surface plasmon-polariton (SR-SPP) resonances setup in individual silver nanoantenna structures at high-spatial resolution with a scanning, subnanometer electron probe. Both even and odd multipolar resonant modes are resolved up to sixth order, and we measure their spatial distribution in relation to nanoantenna structures at energies down to 0.55 eV. Fabry-Perot type SR-SPP reflection phase shifts are calculated from direct measurements of antinode spacings in high-resolution plasmonic field maps. We observe resonant SR-SPP antinode bunching at nanoantenna terminals in high-order resonant modes, and antinode shifts in nonhomogeneous local environments. Finally, we achieve good agreement of our experimental SR-SPP maps with numerical calculations of photon excited near fields, using a novel integrated photon excitation geometry.

Seroprevalence of Toxoplasma gondii among Nunavik Inuit (Canada).

As a result of their intimate contact with the land and their nutritional habits, the Inuit of Nunavik are considered to be at risk from zoonotic infections. To better understand the risk factors for Toxoplasma gondii infection, a serosurvey was conducted in Nunavik, Québec, in September 2004. A representative sample of the Inuit adult population of Nunavik participated in this cross-sectional study (n = 917). Antibodies (IgG) against T. gondii were detected by immunoassay. Information on sociodemographic characteristics, traditional activities, domestic environment and nutrition was gathered by questionnaire and explored as variables explanatory of seropositive results. Associations found to be statistically significant in univariate analyses were assessed by multivariable logistic regression to control for confounding factors. Almost two thirds (59.8%) of the Inuit of Nunavik were found to be seropositive for T. gondii. In multivariate analyses, risk factors for seropositivity were: increasing age, gender (women > men), lower level of education, consumption of potentially contaminated water (determined by an index of risk from waterborne infections), frequent cleaning of water reservoirs, and consumption of seal meat and feathered game. There was some variation in seroprevalence between the Ungava Bay coast (52.3%) and the Hudson Bay coast (65.6%), the two main regions of Nunavik, but this variation was not significant in the multivariable logistic regression model. This cross-sectional study demonstrated high T. gondii seroprevalence in the Inuit population and revealed that age, gender, schooling and community of residence all influence serostatus in this population. Variables related to drinking water and food choices may also influence the risk of infection. These results raise important questions about T. gondii transmission in Nunavik including possible links between terrestrial and marine cycles.

Development and characterization of a continuous cell line, AFKM-On-H, from hemocytes of the European corn borer Ostrinia nubilalis (Hübner) (Lepidoptera, Pyralidae).

The corn borer, Ostrinia nubilalis, is a very important pest in different countries, and the in vitro system of the insect could be a useful tool for isolation and characterization of the pathogens and physiological responses of the insect. In this context, a cell line was derived from the hemocytes of the European corn borer and was named AFKM-On-H for, respectively, O. nubilalis, Armand Frappier, King Mongkut Institutes, and Hemocytes. This cell line was initiated and maintained in Ex-Cell 400 medium supplemented with 10% heat-inactivated fetal bovine serum. The cells, mostly spherical in shape, not firmly attached to the plastic culture flasks, were passaged up to 200 times by repeated gentle pipetting of the cells. The doubling times at the 80th and 125th passages at 28 degrees C and at the 122th and 169th passages at 25 degrees C were 40, 29, 35, and 34 h, respectively. The AFKM-On-H cell line was further characterized by the morphology, karyotype, random amplified polymorphic DNA analysis, and isozyme profiles. Susceptibility of the cell line to cytoplasmic polyhedrosis viruses (CPV) Euxoa scandens (EsCPV), Dendrolimus punctatus (DpCPV), and Choristoneura fumiferana (CfCPV); nuclear polyhedrosis viruses [Autographa californica (AcMNPV) wild type and recombinant, Antherea yammamai (AnyaNPV)]; and Chilo iridescent virus was demonstrated. Relative sensitivities of the cell line to Bacillus thuringiensis and Metarhizium anisopliae toxins and effects of the molting hormone 20-hydroxyecdysone on this new hemocyte cell line were characterized.

A novel tool for high-resolution transmission electron microscopy of intact interfaces between bone and metallic implants.

A key feature in the understanding of the mechanisms of integration versus rejection of implanted materials is a deepened understanding of the elemental and molecular compositions of the interface zone between the surface of the synthetic man-made material and the biological components of tissue. Intact interfaces between metallic implants and tissues have not been able to image and analyse on the ultrastructural level with the common transmission electron microscopy (TEM) sample preparation techniques. By using focused ion beam microscopy for site-specific preparation of TEM samples, intact interfaces between metal implants and calcified tissue were imaged for the first time. The interface's elemental and crystallographic compositions were determined using energy dispersive X-ray mapping and electron diffraction. The developed technique fulfills a long-sought-for demand to correlate the surface properties of implanted metal prostheses with the fine structure and composition of preserved interfaces with tissues.

Most ten-year-old children with negative or unknown histories of chickenpox are immune.

To evaluate the proportion of children to vaccinate against varicella in a catch-up program targeting 9- to 10-year-old children, a study was conducted among children age 10 years to assess the age-specific incidence of varicella and document the immunity against varicella in those with negative or unknown chickenpox history. Of the latter 62% were seropositive for varicella.

Genetic diversity and molecular epidemiology of Norwalk-like viruses.

Specimens (n=287) from 59 gastroenteritis outbreaks collected from February 1997 to March 1999 were analyzed by reverse transcriptase-polymerase chain reaction. The majority of outbreaks (88%) were associated with Norwalk-like viruses. Molecular analyses of strains from 46 outbreaks showed the cocirculation during the 1998-1999 winter of 2 genogroup II clusters, accounting for 57% and 28% of outbreaks, respectively. An important genetic diversity was observed during this 2-year period. Thirteen different genogroup II strains and 3 different genogroup I strains were found. Genogroup I strains, although from the same cluster, were highly divergent (9%-16%). Epidemiologic and molecular data indicate that several introductions did not result in any major shift of prominent strains, whereas 1 apparently established itself. Some point mutations allowed corroboration of epidemiologic links and strongly suggest that, in several instances, sharing staff and/or transfer of patients between health care institutions can create a significant risk for Norwalk-like virus dissemination.

Aeromonas hydrophila isolated from food and drinking water: hemagglutination, hemolysis, and cytotoxicity for a human intestinal cell line (HT-29).

Aeromonas hydrophila isolated from food and drinking water was tested for pathogenicity by studying its hemolysis, hemagglutination, and cytotoxicity. Hemolysis, tested on erythrocytes from six different species, was more frequently seen with water isolates (64%) than with food isolates (48%). Hemagglutination was more frequently encountered with food isolates (92%) than with water isolates (73%). Cytotoxicity, evaluated on seven cell lines, was frequently observed with food isolates (92%) and with water isolates (73%). Heat treatment (56 degrees C for 10 min) of culture supernatant fluids inhibited the toxicity of some but not all toxin-producing isolates. Our results suggest that the human intestinal cell line HT-29 could be a useful complement for testing A. hydrophila exotoxins and for studying the enteropathogenicity of this species for humans.

Cellular immunity in measles vaccine failure: demonstration of measles antigen-specific lymphoproliferative responses despite limited serum antibody production after revaccination.

Measles antigen-specific immune responses were evaluated 1 and 6 months after revaccination in 60 previously vaccinated subjects (9.4 +/- 3.4 years of age) who had either undetectable or low plaque reduction neutralization (PRN) titers (< 200). PRN titers were increased in all subjects at 1 month (590 +/- 61; range, 129-2513) but fell again in 66% of subjects by 6 months (214 +/- 29; range, 30-794). At 6 months, 23 (38%) had subprotective (< 120) or borderline (< 200) PRN titers. Lymphoproliferative responses to measles virus antigens were low overall before revaccination (mean stimulation index [SI], 2.6 +/- 0.4; range, 0.5-13.5) but were readily detectable at 1 (SI, 145.8 +/- 2.6; range, 1.4-80) and 6 months after revaccination (SI, 9.4 +/- 1.8; range, 1.1-87). Before revaccination, 10 of the subjects (50%) with low positive PRN titers had SIs > or = 3. At 6 months after revaccination, 18 subjects (78%) with PRN titers < or = 200 had SIs > or = 3. These data suggest that cellular responses to measles virus may be better sustained than antibody titers after vaccination and revaccination in some subjects.

[The human gastroenteritis virus in the Quebec region (1986-1991). Identification by electronic microscopy]. / Les virus de gastro-entérite humaine dans la région de Québec (1986-1991). Identification par microscopie électronique.

Between 1986 and 1991, 251 fecal samples were examined. Viruses were found in 48% of stools, namely adenoviruses, astroviruses, caliciviruses, coronaviruses, rotaviruses, and particles reassembling the Norwalk agent (74% of positive cases). All morphological types of viruses normally associated with human gastroenteritis are present in Quebec, its vicinity, and in the east of the Province. The interpretation of specimens is complicated by the presence of a wide variety of biological structures including bacteriophages. Electron microscopy is the method of choice for identification of the whole range of gastroenteritis viruses.

Evaluation of variables in immunofluorescence procedures for the detection of antibodies against human herpesvirus 6 (HHV-6).

Ten human sera were used to study different parameters, namely, methods of smear preparation and fixation, and age of infected HSB-2 cells in order to optimize indirect immunofluorescence assay (IFA) and anticomplement immunofluorescence (ACIF) procedures to measure antibody levels against HHV-6. Results showed a greater sensitivity of rapid smear drying and methanol fixation over conventional acetone smear preparation. Cells harvested 6 days after infection and fixed with methanol exhibited a sharper and more intense fluorescence. IFA titers were higher than those obtained with ACIF, although the latter procedure enabled the distinction between three fluorescent sites. Reactivity pattern of individual sera against infected cells was variable and indicated that the human immune response to HHV-6 is directed against different antigens. An easier interpretation and a better definition of the fluorescence of HSB-2 cell line infected with HHV-6 strain Dv is obtained with the following conditions: cells should be harvested at 5-8 days after infection (at the giant cell stage of infection), cell smears have to be dried quickly before fixation with methanol at -20 degrees C, and finally, they should be stained by IFA.

Seroprevalence of antibodies against human herpesvirus 6 in the Quebec City area.

Seroprevalence of antibodies against human herpesvirus 6 was determined in a sample of 303 randomly selected individuals from the Quebec City area. The influence of different variables on antibody litres was also evaluated. Human herpesvirus 6 was grown in the HSB-2 cell line, and antibody litres were measured by indirect immunofluorescence. Serum samples were collected from 177 females and 126 males ranging in age from two months to 88 years. Ninety-nine per cent (300 of 303) of this population had an antibody titre of at least 1:10, whereas 75% had a titre of at least 1:80. Women had a higher geometric mean litre than men (P=0.06). This difference between sexes varied according to age and became statistically significant in subjects older than 20 years of age (P=0.04). It was found that this difference was attributable to higher antibody litres in women in the 15 to 40 year age group who had previously had children.

Why are clinical problems difficult? General practitioners' opinions concerning 24 clinical problems.

This study was conducted to describe the difficulties perceived by general practitioners concerning 24 common clinical problems and to compare their perceptions with those of faculty members in family medicine. A random sample of 467 general practitioners and all 182 faculty members in family medicine in Quebec were sent one of four open-ended questionnaires, each of which dealt with six clinical problems; 214 general practitioners and 114 faculty members participated. A total of 5111 difficulties were reported; the number reported by each subject varied from 0 to 13 (mean 2.6 [standard deviation 2.09]) per problem. The problems that generated the most difficulties were depression, confusion in the elderly, chronic back pain, loss of autonomy in the elderly and sexually transmitted disease. The most frequent difficulties were with the patient's noncompliance with treatment, clinical diagnosis, failure of a specific treatment, inadequate health care resources and the physician's own emotional reactions. The difficulties for each problem were the same in the two groups 70% of the time. Physician's perceptions of their difficulties can be useful in the planning of initial training and continuing medical education.