La bactérie Clostridium difficile est maintenant considérée comme un pathogène majeur responsable d'infections nosocomiales en Amérique du Nord et en Europe. De plus, l'émergence de souches hypervirulentes, telle la souche NAP1/027 responsable de récentes épidémies, est un phénomène inquiétant. Un enjeu crucial au cours des prochaines années sera de mieux comprendre les mécanismes de virulence et d'évolution de C. difficile. Les bactériophages (c.-à-d. des virus bactériens, ou phages) sont des joueurs clés dans l'évolution de la plupart des bactéries, pathogènes ou non. Les données concernant l'impact des phages sur C. difficile sont très limitées. Par contre, deux études récentes démontrent que les phages semblent influencer la virulence de C. difficile en altérant la production de toxines TcdA et TcdB. L'objectif de mes travaux de recherche est donc d'étudier au niveau microbiologique et moléculaire les phages de C. difficile et de démontrer leur impact sur l'évolution et la virulence de ce pathogène. Dans ce contexte, plusieurs phages ont été induits à partir d'isolats cliniques de C. difficile. Dans cette collection, un phage en particulier, le (pCD38-2, a été choisi pour la caractérisation subséquente dû à sa divergence génomique par rapport aux autres phages et à sa capacité d'infecter la grande majorité des souches ayant le ribotype hypervirulent (027). Ces caractéristiques uniques ont justifié le séquençage complet de son génome. Par contre, aucun facteur de virulence évident n'a été identifié. À l'opposé, une analyse bio-informatique a permis l'identification d'une région spécifique comportant plusieurs gènes de conversion lysogénique potentiels. L'impact de ces gènes sur la virulence bactérienne reste à être déterminé. De plus, lorsqu'on introduit le phage cpCD38-2 dans la souche sensible CD274, on observe une accumulation plus rapide et plus grande des toxines après 48h dans le surnageant de la culture. Ce phénomène a été confirmé avec des tests ELISA sur des réplicas biologiques indépendants ainsi que par un immunodosage avec anticorps spécifiques aux deux toxines. Par ailleurs, une étude transcriptionelle par PCR en temps réel a permis de constater que le phage (pCD38-2 influence également l'expression des gènes tcdA et tcdB dans le temps. Par contre, l'effet du phage cpCD38-2 est variable lorsqu'on l'introduit dans d'autres souches de C. difficile. Donc, les résultats de nos travaux indiquent que certains phages auraient un impact sur la virulence de C. difficile en altérant la production et la transcription des gènes de toxines. Nos données laissent toutefois sous-entendre que cet effet peut varier selon les souches de C. difficile. [Symboles non conformes]

Clostridium difficile est un pathogène entérique qui cause d'importantes infections nosocomiales dont le traitement est parfois problématique. Il n'existe, à l'heure actuelle, que deux antibiotiques approuvés pour traiter les infections à C. difficile et le taux de rechute est assez important. Ce projet a initialement visé à isoler et caractériser des phages virulents contre C. difficile en vue de les utiliser en phagothérapies comme outils thérapeutiques alternatifs. Les eaux usées et les selles de patients infectés par C. difficile ont été utilisées pour isoler et détecter les phages virulents. Or, quatre phages différents (9MMPOI-O4) ont été isolés mais aucun de ces phages ne s'est révélé être virulent. Les quatre phages tempérés ont donc été caractérisés et leur impact a été évalué sur quelques phénotypes bactériens chez C. difficile dont la motilité et la production des toxines A et B. La caractérisation morphologique des phages (pMMPOl-04 a permis de déterminer que ceux-ci appartiennent à la familles des Myoviridae alors que la caractérisation génomique a permis de démontrer que certains de ces phages sont assez différents entre eux mais également par rapport aux autres phages tempérés, isolés et caractérisés dans la littérature. De façon générale, les phages (pMMPOl-04 ne semblent pas s'induire spontanément de manière plus importante mais suggère que la présence de certains antibiotiques pourrait augmenter l'induction de certains de ces phages. L'impact des phages (pMMPOl-04 sur la motilité chez C. difficile n'a pas démontré que ceux-ci avaient un rôle à jouer sur ce phénotype. Par contre, certains des phages (pMMP semblent augmenter ou diminuer la production en toxines A et B. Les résultats de nos travaux indiquent donc que certains des phages caractérisés présentent des différences importantes qui suggèrent une grande diversité parmi les phages tempérés chez C. difficile. De plus, certains des phages cpMMP auraient la capacité de participer aux transferts horizontaux de matériels génétiques et d'affecter la régulation de certains facteurs de virulence chez C. difficile tel que la production en toxines A et B. Évidemment, des travaux supplémentaires seront nécessaires pour confirmer la modification du phénotype de production en toxines par ces phages mais également sur d'autres phénotypes associés aux autres facteurs de virulence de cette bactérie. [Symboles non conformes]

Clostridium difficile infection (CDI) is the leading cause of bacterial infectious diarrhea in nosocomial settings and approximately 25% of patients with CDI experience disease recurrence. Prior CDI epidemiological investigations are limited though. They do not reflect the burden of CDI in federal facilities, nor do they capture recent estimates on patient health outcomes. Furthermore, few studies have integrated CDI recurrence risk factors into a tool that clinicians can use to identify patients at risk for CDI recurrence. This study 1) described the epidemiology of CDI in the national Veterans Health Administration (VHA), 2) derived and validated a clinical prediction rule for 60-day CDI first recurrence, and 3) derived and validated a clinical prediction rule for 60-day CDI second recurrence. This was a retrospective cohort study of VHA beneficiaries with CDI between October 1, 2001 and September 30, 2012. VHA clinical and pharmacy data were integrated to develop several independent variables, including patient baseline demographics, CDI characteristics, comorbidities, concomitant medications, prior medications, prior hospitalization, hospital length of stay (LOS), and CDI severity. The dependent variables included 30/60/90-day mortality, and 30/60/90-day CDI recurrence. CDI incidence and outcomes were presented descriptively and compared using generalized linear regression models. CDI recurrence prediction rules were derived using multivariable logistic regression models and validated using the area under the receiver-operating-characteristic curve (AUROC), sensitivity, specificity, positive predictive value, and negative predictive value. Our study demonstrated that CDI first episodes, recurrences, and severity increased over the study period, while mortality decreased. Our CDI first recurrence prediction rule included the following predictor variables: dyslipidemia, CDI type, renal disease, hospital LOS <7 days, principal CDI diagnosis, concomitant gastric acid suppressors, and concomitant antibiotics. This model demonstrated moderate 60-day first recurrence discrimination (AUROC=0.62). Our CDI second recurrence prediction rule was similar in predictor variables and validity. In conclusion, CDI is an important, rapidly-emerging public health problem in the VHA. A clinical prediction rule might aid clinicians in directing preventative therapies to patients at high risk for CDI recurrence. / text

Class of 2012 Abstract / Specific Aims: The incidence of non-response, recurrence, relapse, and rate of complications of Clostridium difficile infections treated with combination of metronidazole and vancomycin versus vancomycin or metronidazole alone over a one-year period by treatment and strain type (i.e. NAP1/BI/027) were evaluated. The incidence of mortality in patients with moderate to severe Clostridium difficile associated diarrhea prescribed metronidazole, vancomycin, or combination metronidazole plus vancomycin as initial therapy was also determined. Additionally, significant factors associated with the use of combination vancomycin-metronidazole as initial therapy for moderate to severe CDAD were characterized. Methods: T This retrospective medical record review has been approved by the Institutional Review Board. Adult patients with stool specimens tested for detection of Clostridium difficile toxin B by PCR between April 2010 and March 2011 at a tertiary care, academic medical center were evaluated. Patients were included in the study if diagnosed with moderate to severe disease and received either monotherapy with metronidazole, monotherapy with oral vancomycin, or combination therapy with metronidazole and oral vancomycin for at least 80% of the first 10 days of treatment. Patients who are discharged alive within 72 hours of admission or who received therapy for less than 48 hours were excluded. Main Results: All patients (N=411) with laboratory evidence of Clostridium difficile during the study time period were evaluated. A total of 26 subjects who received oral vancomycin monotherapy and 56 subjects who received oral vancomycin along with metronidazole for at least 80% of the first 10 days of treatment were identified. Of the subjects who received oral vancomycin monotherapy during the first ten days of therapy, 5 (19%) were classified has a treatment failure or died within the first 21 days of therapy and 5 (19%) had either a recurrence or reappearance of Clostridium difficile associated diarrhea between 22 and 65 days post start of therapy. Of the subjects who received a combination of oral vancomycin and metronidazole during the first 10 days of therapy, 14 (25%) were classified has a treatment failure or died within the first 21 days of therapy and 22 (39%) had either a recurrence or reappearance of Clostridium difficile associated diarrhea between 22 and 65 days post start of therapy. In the combination therapy group, 5 (9%) were reported to have an ileus, toxic megacolon, or necrotic bowel during the first 10 days of therapy. Conclusions: In this study, the subjects who received a combination of oral vancomycin and metronidazole had higher rates of clinical failure, death, and recurrence than subjects who received monotherapy. Current guideline statements recommend combination therapy only in patients with an ileus with Clostridium difficile-associated diarrhea.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / OBJECTIVE: An estimated 20-30% of patients with primary Clostridium difficile infection (CDI) develop recurrent CDI (rCDI) within 2 weeks of completion of therapy. While the actual mechanism of recurrence remains unknown, a variety of risk factors have been suggested and studied. The aim of this systematic review and meta-analysis was to evaluate current evidence on the risk factors for rCDI. DESIGN: We searched MEDLINE and 5 other databases for subject headings and text related to rCDI. All studies investigating risk factors of rCDI in a multivariate model were eligible. Information on study design, patient population, and assessed risk factors were collected. Data were combined using a random-effects model and pooled relative risk ratios (RRs) were calculated. RESULTS: A total of 33 studies (n=18,530) met the inclusion criteria. The most frequent independent risk factors associated with rCDI were age≥65 years (risk ratio [RR], 1.63; 95% confidence interval [CI], 1.24-2.14; P=.0005), additional antibiotics during follow-up (RR, 1.76; 95% CI, 1.52-2.05; P<.00001), use of proton-pump inhibitors (PPIs) (RR, 1.58; 95% CI, 1.13-2.21; P=.008), and renal insufficiency (RR, 1.59; 95% CI, 1.14-2.23; P=.007). The risk was also greater in patients previously on fluoroquinolones (RR, 1.42; 95% CI, 1.28-1.57; P<.00001). CONCLUSIONS: Multiple risk factors are associated with the development of rCDI. Identification of modifiable risk factors and judicious use of antibiotics and PPI can play an important role in the prevention of rCDI.

No description available.

Reproduction de : Mémoire du DES : Pharmacie spécialisée : Nantes : 2009. Reproduction de : Thèse d'exercice : Pharmacie : Nantes : 2009. / Bibliogr.

published_or_final_version / Microbiology / Master / Master of Medical Sciences

No description available.

Clostridium difficile infection (CDI) is a disease associated with the wide-spread use of antibiotics and causes 450,000 infections and almost 30,000 deaths in the United States annually. Recurrence is a major problem, with approximately 1/3rd of patients relapsing after antibiotic treatment for CDI. Fecal Microbiota Transplantation (FMT) has emerged as a novel therapy for recurrent CDI, but the majority of the literature to date is made up of uncontrolled case series, so FMT’s true efficacy compared with standard antibiotic regimens remains unknown. Only a few randomized control trials (RCTs) have been published, and these have studied small numbers of patients and exhibited marked methodological heterogeneity. As such, there is uncertainty about the appropriate indications for FMT with respect to recurrent CDI, as well as the best methodology for the procedure, which has been carried our using various fecal preparations and modes of delivery. In particular, questions remain about if FMT should be recommended for patients with a first CDI recurrence, and if minimally invasive methods of performing FMT such as administration of enteric coated capsules are more efficacious than standard antibiotic treatments. We propose a double blind, placebo controlled, RCT that will be run as two parallel RCTs, where Trial 1 will enroll patients experiencing a first CDI recurrence, and Trial 2 will enroll patients experiencing a second or later CDI recurrence. The treatment arms in each trial will receive FMT in the form of orally administered frozen capsules, while the control arms will receive standard antibiotic treatments based on the number of recurrences they have experienced. If shown to be efficacious in a large RCT, oral capsulized FMT alone as treatment for recurrent CDI has the potential to increase access to FMT, decrease unnecessary antibiotic use, and substantially reduce morbidity and mortality attributable to CDI.