Nathalie Turgeon

Host and Pathogen Factors for Clostridium difficile Infection and Colonization

BACKGROUND Clostridium difficile infection is the leading cause of health care-associated diarrhea, and the bacterium can also be carried asymptomatically. The objective of this study was to identify host and bacterial factors associated with health care-associated acquisition of C. difficile infection and colonization. METHODS We conducted a 15-month prospective study in six Canadian hospitals in Quebec and Ontario. Demographic information, known risk factors, potential confounding factors, and weekly stool samples or rectal swabs were collected. Pulsed-field gel electrophoresis (PFGE) was performed on C. difficile isolates to determine the genotype. Levels of serum antibodies against C. difficile toxins A and B were measured. RESULTS A total of 4143 patients were included in the study; 117 (2.8%) and 123 (3.0%) had health care-associated C. difficile infection and colonization, respectively. Older age and use of antibiotics and proton-pump inhibitors were significantly associated with health care-associated C. difficile infection. Hospitalization in the previous 2 months; use of chemotherapy, proton-pump inhibitors, and H(2) blockers; and antibodies against toxin B were associated with health care-associated C. difficile colonization. Among patients with health care-associated C. difficile infection and those with colonization, 62.7% and 36.1%, respectively, had the North American PFGE type 1 (NAP1) strain. CONCLUSIONS In this study, health care-associated C. difficile infection and colonization were differentially associated with defined host and pathogen variables. The NAP1 strain was predominant among patients with C. difficile infection, whereas asymptomatic patients were more likely to be colonized with other strains. (Funded by the Consortium de Recherche sur le Clostridium difficile.).

Carbapenem-resistant Gram-negative bacilli in Canada 2009–10: results from the Canadian Nosocomial Infection Surveillance Program (CNISP)

OBJECTIVES To investigate the occurrence and molecular mechanisms associated with carbapenemases in carbapenem-resistant Gram-negative isolates from Canadian cases. METHODS Twenty hospital sites across Canada submitted isolates for a 1 year period starting 1 September 2009. All Enterobacteriaceae with MICs ≥ 2 mg/L and Acinetobacter baumannii and Pseudomonas aeruginosa with MICs ≥ 16 mg/L of carbapenems were submitted to the National Microbiology Laboratory (NML) where carbapenem MICs were confirmed by Etest and isolates were characterized by PCR for carbapenemase genes, antimicrobial susceptibilities, PFGE and plasmid isolation. RESULTS A total of 444 isolates (298 P. aeruginosa, 134 Enterobacteriaceae and 12 A. baumannii) were submitted to the NML of which 274 (61.7%; 206 P. aeruginosa, 59 Enterobacteriaceae and 9 A. baumannii) met the inclusion criteria as determined by Etest. Carbapenemase genes were identified in 30 isolates: bla(GES-5) (n = 3; P. aeruginosa), bla(KPC-3) (n = 7; Enterobacteriaceae), bla(NDM-1) (n = 2; Enterobacteriaceae), bla(VIM-2) and bla(VIM-4) (n = 8; P. aeruginosa) bla(SME-2) (n = 1; Enterobacteriaceae) and bla(OXA-23) (n = m9; A. baumannii). PFGE identified a cluster in each of Enterobacteriaceae, P. aeruginosa and A. baumannii corresponding to isolates harbouring carbapenemase genes. Three KPC plasmid patterns (IncN and FllA) were identified where indistinguishable plasmid patterns were identified in unrelated clinical isolates. CONCLUSIONS Carbapenemases were rare at the time of this study. Dissemination of carbapenemases was due to both dominant clones and common plasmid backbones.

Comparison of Five Bacteriophages as Models for Viral Aerosol Studies

ABSTRACT Bacteriophages are perceived to be good models for the study of airborne viruses because they are safe to use, some of them display structural features similar to those of human and animal viruses, and they are relatively easy to produce in large quantities. Yet, only a few studies have investigated them as models. It has previously been demonstrated that aerosolization, environmental conditions, and sampling conditions affect viral infectivity, but viral infectivity is virus dependent. Thus, several virus models are likely needed to study their general behavior in aerosols. The aim of this study was to compare the effects of aerosolization and sampling on the infectivity of five tail-less bacteriophages and two pathogenic viruses: MS2 (a single-stranded RNA [ssRNA] phage of the Leviviridae family), Φ6 (a segmented double-stranded RNA [dsRNA] phage of the Cystoviridae family), ΦX174 (a single-stranded DNA [ssDNA] phage of the Microviridae family), PM2 (a double-stranded DNA [dsDNA] phage of the Corticoviridae family), PR772 (a dsDNA phage of the Tectiviridae family), human influenza A virus H1N1 (an ssRNA virus of the Orthomyxoviridae family), and the poultry virus Newcastle disease virus (NDV; an ssRNA virus of the Paramyxoviridae family). Three nebulizers and two nebulization salt buffers (with or without organic fluid) were tested, as were two aerosol sampling devices, a liquid cyclone (SKC BioSampler) and a dry cyclone (National Institute for Occupational Safety and Health two-stage cyclone bioaerosol sampler). The presence of viruses in collected air samples was detected by culture and quantitative PCR (qPCR). Our results showed that these selected five phages behave differently when aerosolized and sampled. RNA phage MS2 and ssDNA phage ΦX174 were the most resistant to aerosolization and sampling. The presence of organic fluid in the nebulization buffer protected phages PR772 and Φ6 throughout the aerosolization and sampling with dry cyclones. In this experimental setup, the behavior of the influenza virus resembled that of phages PR772 and Φ6, while the behavior of NDV was closer to that of phages MS2 and ΦX174. These results provide critical information for the selection of appropriate phage models to mimic the behavior of specific human and animal viruses in aerosols.

The laval questionnaire: a new instrument to measure quality of life in morbid obesity

BackgroundOur recent review of the literature uncovered eleven obesity-specific quality of life questionnaires, all with incomplete demonstration of their measurement properties. Our objective was to validate a new self-administered questionnaire specific to morbid obesity to be used in clinical trials. The study was carried out at the bariatric surgery clinic of Laval Hospital, Quebec City, Canada.MethodsThis study followed our description of health-related quality of life in morbid obesity from which we constructed the Laval Questionnaire. Its construct validity and responsiveness were tested by comparing the baseline and changes at 1-year follow-up in 6 domain scores (symptoms, activity/mobility, personal hygiene/clothing, emotions, social interactions, sexual life) with those of questionnaires measuring related constructs (SF-36, Impact of Weight on Quality of Life-Lite, Rosenberg Self-Esteem Scale and Beck Depression Inventory-II).Results112 patients (67 who got bariatric surgery, 45 who remained on the waiting list during the study period) participated in this study. The analysis of the discriminative function of the questionnaire showed moderate-to-high correlations between the scores in each domain of our instrument and the corresponding questionnaires. The analysis of its evaluative function showed (1) significant differences in score changes between patients with bariatric surgery and those without, and (2) moderate-to-high correlations between the changes in scores in the new instrument and the changes in the corresponding questionnaires. Most of these correlations met the a priori predictions we had made regarding their direction and magnitude.ConclusionThe Laval Questionnaire is a valid measure of health-related quality of life in patients with morbid obesity and is responsive to treatment-induced changes.

Predictors of asymptomatic Clostridium difficile colonization on hospital admission

BACKGROUND Clostridium difficile (CD) is the leading cause of health care-associated diarrhea and can result in asymptomatic carriage. Rates of asymptomatic CD colonization on hospital admission range from 1.4%-21%. The objective of this study was to evaluate host and bacterial factors associated with colonization on admission. METHODS The Consortium de recherche québécois sur le Clostridium difficile study provided data for analysis, including demographic information, known risk factors, and potential confounding factors, prospectively collected for 5,232 patients from 6 hospitals in Quebec and Ontario over 15 months from 2006-2007. Stool or rectal swabs were obtained for culture on admission. Pulsed-field gel electrophoresis was performed on the isolates. The presence of antibody against CD toxins A and B was measured. RESULTS There were 212 (4.05%) patients colonized with CD on admission, and 5,020 patients were not colonized with CD. Multivariate logistic regression analysis showed that hospitalization within the last 12 months, use of corticosteroids, prior CD infection, and presence of antibody against toxin B were associated with colonization on admission. Of patients colonized on admission, 79.4% had non-NAP1, non-NAP2 strains. CONCLUSION There are identifiable risk factors among asymptomatic CD carriers that could serve in their detection and provide a basis for targeted screening.

Evaluation of the plasmid copy number in B. cereus spores, during germination, bacterial growth and sporulation using real-time PCR.

Only a small number of studies have measured the plasmid copy number (PCN) variation during bacterial growth. Besides, information about the PCN in spores is still rare. In this work, we utilized a real-time PCR assay to evaluate the PCN of four different plasmids in Bacillus cereus. The PCN was measured in spores as well as during germination, active bacterial growth, and sporulation. Plasmid stability was also evaluated to ensure that plasmid loss does not affect the accuracy of the PCN measurement. We demonstrated that the PCN of low and high copy number plasmids varies with growth phase as well as culture media over B. cereus life cycle. The PCN was minimum during the germination and maximum during the stationary growth phase for all plasmids tested. We also demonstrated that the use of antibiotic in the culture media is not enough to ensure stable inheritance in spores of plasmids carrying antibiotic resistance genes. Moreover, we revealed that the PCN in spores is related to the PCN during endospores formation. Therefore, the plasmid partitioning during sporulation is not influenced by the unequal-size of the forespores and the mother cells, even for a plasmid distributed randomly.

Permeabilization and hybridization protocols for rapid detection of Bacillus spores using fluorescence in situ hybridization.

BACKGROUND Fluorescence in situ hybridization (FISH) is not adapted for the detection of bacterial spores because of their resistance to conventional permeabilization treatments. Since spore-forming bacteria have important ecological, economical, and medical roles, their in situ detection needs to be improved. The aim of this study was to develop rapid and effective protocols to permeabilize Bacillus spores in order to apply the FISH technique. METHODS Permeabilization protocols were developed for three species of Bacillus spores. Hybridization was performed using universal and specific probes. Surface structural analysis of the permeabilization treatments was performed using scanning electron microscopy. RESULTS With the proposed protocols, Bacillus spores can be labeled in less than 1 h. The scanning microscopy showed some visible structural differences between the permeabilized spores compared to intact ones. CONCLUSION For the first time, rapid and effective protocols to detect Bacillus spores by FISH were developed and can be applied to study Bacillus spores using in situ labeling within 1 h. Previously published in situ hybridization protocols have never reached or been close to the currently described rapidity. This work will contribute to the possibility of near real time detection of biological threats that may be present as spores.

Role of galK and galM in Galactose Metabolism by Streptococcus thermophilus

ABSTRACT Streptococcus thermophilus is unable to metabolize the galactose moiety of lactose. In this paper, we show that a transformant of S. thermophilus SMQ-301 expressing Streptococcus salivarius galK and galM was able to grow on galactose and expelled at least twofold less galactose into the medium during growth on lactose.

Resistance of Aerosolized Bacterial Viruses to Relative Humidity and Temperature.

ABSTRACT The use of aerosolized bacteriophages as surrogates for hazardous viruses might simplify and accelerate the discovery of links between viral components and their persistence in the airborne state under diverse environmental conditions. In this study, four structurally distinct lytic phages, MS2 (single-stranded RNA [ssRNA]), ϕ6 (double-stranded RNA [dsRNA]), ϕX174 (single-stranded DNA [ssDNA]), and PR772 (double-stranded DNA [dsDNA]), were nebulized into a rotating chamber and exposed to various levels of relative humidity (RH) and temperature as well as to germicidal UV radiation. The aerosolized viral particles were allowed to remain airborne for up to 14 h before being sampled for analysis by plaque assays and quantitative PCRs. Phages ϕ6 and MS2 were the most resistant at low levels of relative humidity, while ϕX174 was more resistant at 80% RH. Phage ϕ6 lost its infectivity immediately after exposure to 30°C and 80% RH. The infectivity of all tested phages rapidly declined as a function of the exposure time to UVC radiation, phage MS2 being the most resistant. Taken altogether, our data indicate that these aerosolized phages behave differently under various environmental conditions and highlight the necessity of carefully selecting viral simulants in bioaerosol studies.

Neuraminidase Activity as a Potential Enzymatic Marker for Rapid Detection of Airborne Viruses

Viruses offer a limited range of targets for their detection. To date, PCR and RT-PCR have been widely used for detection of viruses. In the case of environmental air sampling, the ability to detect a broad range of viruses would constitute a significant advantage for preventing outbreaks of airborne-transmitted viral infections. Given that neuraminidase is found on some respiratory virus species of medical or agricultural importance, this enzyme could theoretically be used to detect several different airborne viruses in a single assay. The aim of the present study was to evaluate the potential of neuraminidase activity as a marker for rapid detection of airborne viruses. We first validated the use of a low-pathogenic strain of Newcastle disease virus (NDV) as a model airborne virus. Our findings revealed that neuraminidase activity-based assays are almost as sensitive as RT-PCR assays currently used for detection of NDV. We also validated the utilization of a neuraminidase substrate specific to viral neuraminidase. Experiments conducted in a controlled chamber demonstrated that the neuraminidase activity is preserved after aerosolization, air sampling using impingement and handling. Finally, we tested our method with swine barn air samples. Our results demonstrate that neuraminidase activity-based assays are suitable for detection of viruses in air samples.