Clostridium difficile infection (CDI) has proven to be a constantly evolving disease periodically posing new diagnostic and clinical dilemmas. Different regions of the world have reported specific local genomic characteristics of the infecting strains, which may be related to variation in disease presentation and outcome. This study was performed to determine the clinical and molecular features of severe, recurrent and community-associated disease in the Lothian region of Scotland, UK among patients diagnosed from August 2010-July 2011. Three hundred and thirty-five patients with laboratory confirmed CDI were studied for epidemiological features, clinical presentation, and laboratory markers. They were followed up for one year to determine recurrence and mortality. Four hundred and thirty-two episodes were recorded. Ribotypes, presence of toxin genes and MLVA subtypes of isolates from these episodes were determined. During the course of the study, PCR ribotype 078 was identified as an important emerging type and concerns of “hypervirulence” were raised when an outbreak was recorded in 2012. This ribotype was studied to compare its clinical and molecular characteristics with other endemic ribotypes and between its own outbreak-related and endemic subtypes. Asymptomatic children were also sampled to determine their role as pools of potential pathogens. Severe episodes accounted for 40.4% of total and 29.3% patients had multiple episodes on record. One-year mortality was 32.8% of which CDI was listed on 25.5% death certificates. Ribotype 078 was confirmed in 6.8% episodes. Community-associated disease was identified in 25.3% patients, which differed significantly from hospital-associated disease in the number of antibiotics and gastrointestinal manipulation prior to CDI. Endemic PCR ribotype 078 caused significantly less recurrent disease and more community- associated disease when compared to the most prevalent ribotype 001. Patients who died from ribotype 078 within 30d had a lower Charlson comorbidity index than ribotype 001 counterparts suggesting that the former may infect healthier patients. MLVA subtyping of ribotype 078 proved useful in identifying epidemiological relationships during the outbreak. CDI had contributed to the death of 50% of all patients infected with the outbreak related ribotype 078 strain compared to 14.3% of those infected with the endemic strains. This study documents the changing epidemiology of CDI in the region and demonstrates differences in epidemic and endemic disease.

There is significant concern about the accumulation of potentially toxic elements (PTEs) in soils because of both direct and indirect impacts on human and ecosystem health. Knowledge of the fate and distribution of such contamination can lead to an effective assessment of the hazards to soil biota and the need for protective or mitigation activities. This is a particular challenge due to the heterogeneity of the soil matrix and complexity of the processes that determine PTE availability to soil biota. While whole-cell bacterial biosensors have been proposed as tools in enabling greater confidence in addressing such biological and chemical interfaces their genuine value remains to be realised. The underpinning objective of this work was to link the response of microbial biosensors to detailed chemical analysis and to relate the dose response sensitivity to other biological measurements. To better understand the phenomena of PTE bioavailability, the study considered changes in toxicity within the context of ion competition in both freshly amended and historically impacted soils. The interaction of test bacteria with both free (soil pore water) and sorbed (solid phase) fractions of the target analytes (copper, nickel and zinc) has enabled a better estimation of bioavailability/toxicity of PTEs in soils. In comparison to other assays, the responses of the microbial sensor to Cu, Ni and Zn highlighted its relative sensitivity to PTE contamination. The use of luminescence marked microbial sensors complements the performance of rigorous analytical soil chemistry approaches. Their value in soil pollution should be considered a technique that should be interpreted alongside chemical analysis rather than an alternative as their performance in complex environmental matrixes is yet to be validated.

Class of 2009 Abstract / OBJECTIVES: The purpose of the study was to determine the rate of Clostridium difficile infections (CDI) in hospitalized patients and the various factors that were associated with the risk of developing CDI by examining patient discharge data for hospitals in 37 states in the United States using Healthcare Cost and Utilization Project (HCUP). METHODS: Patient discharge information for all patients obtained using HCUP census for the years 2002-2005, either for primary or secondary (all-listed) occurrences of CDI using the ICD-9-CM code (008.45) specific for intestinal infections due to C. difficile, were included in the study. Regression analysis, either Generalized Linear Model log-link or power-link, or a logistic regression was employed to control for the multiple independent variables. RESULTS: The incidence rate for CDI was 9.4% for the years 2002-2005. Among the concomitant diagnoses and procedures, essential hypertension, volume depletion, congestive heart failure, urinary tract infection and venous catheterization were the top 5. The length of stay (LOS) for CDI was associated with being Black, Hispanic or Other race category, number of diagnoses and procedures, primary expected payer of Medicaid, private insurance and other (including worker’s compensation, CHAMPUS,CHAMPVA etc), and all groups classified based on median household income category for patient’s zip code. Predictors of CDI related to inpatient total hospital charges were being female, race (other than black), number of diagnoses and procedures, Death, LOS, patient location and with self-pay and no charge categories as primary expected payer. Predictors of higher CDI related inpatient hospital deaths were age, female sex, Hispanic race, number of diagnoses and procedures, LOS and having Medicaid, self-pay or other as primary expected payer. CONCLUSIONS: LOS, inpatient total hospital charges, and inpatient mortality were dependent on several patient and other characteristics.

No description available.

La mammite bovine est l’inflammation des tissus internes de la glande mammaire des vaches laitières. Elle est la plupart du temps causée par l’intrusion d’agents pathogènes dans le canal du trayon de la glande mammaire causant ainsi une infection intramammaire (IIM). La mammite engendre des pertes économiques importantes pour l’industrie laitière en raison de la faible production du lait, des coûts de traitements élevés, la présence de résidus d’antibiotiques dans le lait suite à leur utilisation, le rejet de lait non destiné à la consommation et les faibles taux de rendement pendant la transformation du lait en divers produits laitiers. Le développement de l’inflammation est souvent associé au degré d’exposition des glandes mammaires aux pathogènes. Staphylococcus aureus est le pathogène le plus souvent responsable de la mammite bovine au Canada. Il est capable de causer des infections intramammaires persistantes sous-cliniques souvent réfractaires à l’antibiothérapie. En outre, le biofilm représente un facteur de virulence clé dans la persistance de S. aureus pendant la mammite, car il augmente la résistance des bactéries contre les antibiotiques grâce à la matrice extracellulaire qui recouvre et protège la communauté. Le biofilm représente donc, une problématique majeure de l’industrie laitière et le besoin de nouveaux outils thérapeutiques alternatifs adressant ce facteur de virulence est très urgent. Le chitosane est une molécule naturelle extraite de la carapace des crustacés. Elle est exploitée pour de multiples applications biologiques, y compris certaines activités antibiofilm. Dans cette étude, nous avons démontré que les formes de 2,6 kDa et 4 kDa empêchaient la production de biofilm des souches : S. aureus 2117 (forte productrice du biofilm) et le SARM bovin (S. aureus résistant à la méthicilline). Chez la souris, l’administration d’un chitosane de 2,6 kDa n’a démontré aucun effet inflammatoire comparativement au 4 kDa. Les tests de bactéricidie ont démontré que le 2,6 kDa était capable de tuer les bactéries incorporées dans les biofilms préformés d'une manière dose-réponse avec une réduction de > 3 log[indice inférieur 10] CFU / biofilm à la concentration de 4 mg / ml. En culture cellulaire, nous avons observé que le chitosane de 2,6 kDa pouvait empêcher la persistance du SARM bovin dans les cellules épithéliales bovines MAC-T. Les tests de combinaison sur plaque ont révélé que le 2,6 kDa produit une synergie avec les antibiotiques de la classe des macrolides (par exemple, la tilmicosine) contre S. aureus, en réduisant la CMI des deux molécules par 2-8 fois. Finalement, l'administration intramammaire de 2,6 kDa, seul (p <0,01) ou en combinaison avec la tilmicosine (p <0,0001), a réduit la colonisation de S. aureus dans les glandes mammaires de notre modèle de mammite aigu murin.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Healthcare acquired infections (HAIs) are a complex and multi-factorial problem associated with high morbidity, mortality, and cost. Toothbrushes (TBs) may be at risk for contamination with potential pathogenic microorganisms (PPMs) from the patient care environment or autoinnoculation from the patient. We focused on three PPMs: multiply resistant Staphylococcus aureus (MRSA), vancomycin resistant Enterococcus (VRE), and Acinetobacter. Specific aims were to (1) describe environmental factors associated with TB contamination in the ICU; (2) describe the relationship between TB contamination and oral colonization in critically ill adults.

Infections in patients with acute liver failure (ALF) and acute liver injury (ALI) are a frequent occurrence. Because ALF and ALI patients share many of the same clinical features as patients with severe sepsis and septic shock, identifying an infection based upon clinical manifestations is extremely difficult. Bacterial culture and sensitivity reports require 24 to 72 hours to be finalized after the need for a culture is suspected and obtained. During this time period, ALF and ALI patients are either not receiving required antibiotic therapy, receiving antibiotic therapy that is not required or not appropriate for the infecting bacterial pathogen, or receiving the correct antibiotic prophylaxis. Receiving an antibiotic that is not needed or inappropriate adds another level of complexity to the ALF and ALI patients because antibiotics may exacerbate liver dysfunction. The purpose of this study was to determine the utility of serum procalcitonin concentrations (SPCTC) as a biomarker of bacterial infections in patients with acute liver failure (ALF) and acute liver injury (ALI). This three part study measured SPCTC retrospectively on samples from ALF and ALI patients who were prospectively enrolled in the United States Acute Liver Failure Study Group (USALFSG) ALF and ALI studies. In the first part of the study, subjects were categorized according to how many SIRS continuum components they had and whether there was a documented infection. In the second part, serial samples on subjects who developed infections were identified. And, in the third part, serial samples on subjects diagnosed with infection on day one of the study and categorized based upon transplant free survival (TFS) or death and/or liver transplant (DoT) were identified. Procalcitonin was not found to be useful in identifying infection in the ALF and ALI patient populations. A cut-off for indication of infection was calculated to be 1.62 ng/mL using receiver operator curve (ROC) analysis. Despite the fact that there was an overall increase in SPCTC as the severity of illness increased in patients with a documented infection, there were confounding variables including antibiotic use, missing data, and small sample size that may have contributed to the poor sensitivity and specificity (0.643 and 0.620 respectively) calculated as part of the ROC analysis. SPCTC values appeared to be increased in subject with acetaminophen (APAP) toxicity and may have affected the cut-off, sensitivity, and specificity results. Increased SPCTC values were seen in APAP subjects who did not have a documented infection. It is unknown at this time if the SPCTC were increase due to liver damage, an undiagnosed infection, or as a result of increase cytokine production due to the APAP toxicity. Serial PCT concentrations in patients who achieved TFS showed a greater decrease over time than those of patients who died or received a liver transplant, however, the TFS group contained a large portion of APAP subjects. Further prospective studies are needed to determine the extent of interference with SPCTC in patients with APAP toxicity and to better define the PCT concentration cut-off between infection and no infection in the ALF and ALI populations.

In the past decade, Staphylococcus aureus has developed two distinct vancomycin resistance mechanisms. First, the bacterium is capable of generating a thickened, poorly crosslinked cell wall that creates false targets. These targets cause vancomycin to bind at the periphery of the thickened peptidoglycan, allowing normal cell wall formation to continue at the cell membrane. Second, S. aureus has acquired genes from Enterococcus that encode an alternative stem peptide. The genes, known as van genes, alter the target of vancomycin, rendering vancomycin treatment ineffectual.In this work, we attempted to further characterize both mechanisms of vancomycin resistance. First, a potential link between up-regulated purine biosynthesis and increased vancomycin resistance due to a thickened cell wall was examined. Despite exploration of multiple mechanisms to increase purine levels within the cell, increased purine synthesis did not provide S. aureus with any advantage in the presence of vancomycin. However, during the investigation, purine biosynthesis in S. aureus was further characterized by confirming purr as the repressor of the purine pathway and demonstrating its sensitivity to mutation.Next, the relationship between homotypic oxacillin resistance and increased vancomycin resistance in the absence of the van genes was investigated. Vancomycin passage of two heterotypic methicillin resistant S. aureus (MRSA) caused these strains to convert to homotypic oxacillin resistance in the absence of oxacillin exposure. Additionally, conversion of heterotypic oxacillin resistant strains to homotypy by oxacillin passage increased strain survival in vancomycin. The SOS response was examined as the possible link between conversion to homotypic oxacillin resistance and increasing vancomycin resistance due to a thickened cell wall. The current study, however, detected no induction of the SOS response during vancomycin exposure.Lastly, the relationship between oxacillin resistance and vancomycin resistance due to the acquisition of the van genes was examined. In vitro and in vivo methods were utilized to determine the effectiveness of a combination of β-lactam antibiotics and vancomycin to treat vancomycin resistant S. aureus (VRSA) infections. Combination therapy provided a significant advantage over untreated control or either antibiotic alone in the rabbit model of endocarditis.

In North America, Borrelia burgdorferi is the primary causative agent of Lymedisease which is a growing health concern. The ability of B. burgdorferi to maintain chronic infection indicates that they are capable of immune evasion. A distinguishing characteristic of B. burgdorferi is the large number of sequences encoding predicted or known lipoproteins, including outer surface protein F (OspF). This study analyzes the specificity of the humoral immune response to B. burgdorferi B3 IMI OspF proteins during murine and human infection. Immunoblot analyses revealed a temporal expression of OspF proteins during infection and mapped the immunodominant epitopes which lie within the variable domains. To determine if OspF-related proteins are produced by other isolates, immunoblot analyses were performed using sera collected from mice and humans infected with diverse B. burgdorferi strains. Differences in the immunoreactivity profile to OspF proteins were seen among the infection sera tested. To identify the molecular basis of these differences, the ospF gene was isolated from several strains, sequenced and evolutionary analyses were conducted. These analyses revealed that OspF proteins show little diversity despite the separate geographic locations from which isolates originated. The high degree of OspF protein conservation seen in isolates from two distinct regions emphasizes the potential for OpsF proteins as vaccinogens or in serodiagnostic assays. Altogether, this study demonstrates the potential contribution of OspF proteins to immune evasion through its temporal expression during infection which may play specific roles at different stages of infection. Studies are underway to determine if inactivation of ospF genes through allelic exchange mutagenesis impacts on the pathogenicity of the Lyme disease spirochetes.