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1.
PLoS Negl Trop Dis ; 18(3): e0012022, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38484041

RESUMEN

Pacific Island countries have experienced periodic dengue, chikungunya and Zika outbreaks for decades. The prevention and control of these mosquito-borne diseases rely heavily on control of Aedes aegypti mosquitoes, which in most settings are the primary vector. Introgression of the intracellular bacterium Wolbachia pipientis (wMel strain) into Ae. aegypti populations reduces their vector competence and consequently lowers dengue incidence in the human population. Here we describe successful area-wide deployments of wMel-infected Ae. aegypti in Suva, Lautoka, Nadi (Fiji), Port Vila (Vanuatu) and South Tarawa (Kiribati). With community support, weekly releases of wMel-infected Ae. aegypti mosquitoes for between 2 to 5 months resulted in wMel introgression in nearly all locations. Long term monitoring confirmed a high, self-sustaining prevalence of wMel infecting mosquitoes in almost all deployment areas. Measurement of public health outcomes were disrupted by the Covid19 pandemic but are expected to emerge in the coming years.


Asunto(s)
Aedes , Virus del Dengue , Dengue , Wolbachia , Infección por el Virus Zika , Virus Zika , Animales , Humanos , Aedes/genética , Aedes/microbiología , Mosquitos Vectores/genética , Mosquitos Vectores/microbiología , Wolbachia/genética , Fiji/epidemiología , Vanuatu
2.
J Vet Diagn Invest ; 35(6): 645-654, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-37705301

RESUMEN

American foulbrood (AFB) is an infectious disease of honey bee brood caused by the endospore-forming bacterium Paenibacillus larvae. P. larvae spores are resilient in the environment, thus colonies with clinical signs of AFB are often destroyed by burning to eradicate the causative agent. To prevent outbreaks of AFB, oxytetracycline metaphylaxis is widely used in North America, resulting in sustained selective pressure for oxytetracycline resistance in P. larvae. To determine if antimicrobial resistance (AMR) is present among P. larvae isolates from commercial beekeeping operations in Saskatchewan, Canada, we performed antimicrobial susceptibility testing of 718 P. larvae samples cultured from pooled, extracted honey collected from 52 beekeepers over a 2-y period, 2019 and 2020. We found that 65 of 718 (9%) P. larvae samples collected from 8 beekeepers were resistant to oxytetracycline with minimum inhibitory concentration (MIC) values of 64-256 µg/mL. Eight of 718 (1%) samples from 4 beekeepers had intermediate resistance to oxytetracycline (MIC: 4-8 µg/mL). Susceptibility testing for tylosin and lincomycin indicated that P. larvae in Saskatchewan continue to be susceptible to these antimicrobials (tylosin MIC: <1 µg/mL, lincomycin MIC: ≤2 µg/mL). Most oxytetracycline-resistant P. larvae samples were identified in northeastern Saskatchewan. Whole-genome sequence analysis identified the P. larvae-specific plasmid pMA67 with tetracycline-resistance gene tet(L) in 9 of 11 oxytetracycline-resistant P. larvae isolates sequenced. Our results highlight the advantage of using pooled, extracted honey as a surveillance tool for monitoring AMR in P. larvae.


Asunto(s)
Oxitetraciclina , Paenibacillus larvae , Abejas , Estados Unidos , Animales , Oxitetraciclina/farmacología , Paenibacillus larvae/genética , Tilosina/farmacología , Saskatchewan/epidemiología , Apicultura , Antibacterianos/farmacología , Larva/microbiología , Lincomicina
3.
Can Vet J ; 63(9): 935-942, 2022 09.
Artículo en Inglés | MEDLINE | ID: mdl-36060490

RESUMEN

European foulbrood (EFB) disease is an economically important bacterial disease of honey bee larvae caused by enteric infection with Melissococcus plutonius. In this study, we investigated 3 clinical outbreaks of EFB disease in commercial beekeeping operations in western Canada in the summer of 2020 and characterized the Melissococcus plutonius isolates cultured from these outbreaks according to genetic multi-locus sequence type and i n vitro larval pathogenicity. We isolated M. plutonius sequence type 19 from EFB outbreaks in British Columbia and Alberta, and a novel M. plutonius sequence type 36 from an EFB outbreak in Saskatchewan. In vitro larval infection with each M. plutonius isolate was associated with decreased larval survival in vitro by 58.3 to 70.8% (P < 0.001) compared to non-infected controls. Further elucidation of mechanisms of virulence of M. plutonius, paired with epidemiologic investigation, is imperative to improve EFB management strategies and mitigate risks of EFB outbreaks in western Canada.


Enquête sur des isolats de Melissococcus plutonius provenant de trois éclosions de loque e uropéenne dans des exploitations apicoles commerciales de l'Ouest canadien. La loque européenne (EFB) est une maladie bactérienne économiquement importante des larves d'abeilles mellifères causée par une infection entérique par Melissococcus plutonius. Dans cette étude, nous avons enquêté sur trois éclosions cliniques de la maladie EFB dans des exploitations apicoles commerciales dans l'ouest du Canada à l'été 2020 et caractérisé les isolats de Melissococcus plutonius cultivés à partir de ces éclosions selon le typage génomique multilocus et la pathogénicité larvaire in vitro. Nous avons isolé le type de séquence 19 de M. plutonius des éclosions d'EFB en Colombie-Britannique et en Alberta, et une nouvelle séquence de type 36 de M. plutonius d'une éclosion d'EFB en Saskatchewan. L'infection larvaire in vitro avec chaque isolat de M. plutonius était associée à une diminution de la survie larvaire in vitro de 58,3 à 70,8 % (P < 0,001) par rapport aux témoins non infectés. Une élucidation plus poussée des mécanismes de virulence de M. plutonius, associée à une enquête épidémiologique, est impérative pour améliorer les stratégies de gestion de l'EFB et atténuer les risques d'épidémies d'EFB dans l'Ouest canadien.(Traduit par Dr Serge Messier).


Asunto(s)
Apicultura , Enterococcaceae , Alberta , Animales , Abejas , Brotes de Enfermedades/veterinaria , Enterococcaceae/genética , Larva/microbiología
4.
Sci Rep ; 12(1): 8848, 2022 05 25.
Artículo en Inglés | MEDLINE | ID: mdl-35614119

RESUMEN

Paenibacillus larvae, the causative agent of American foulbrood (AFB), produces spores that may be detectable within honey. We analyzed the spore content of pooled, extracted honey from 52 large-scale (L) and 64 small-scale (S) Saskatchewan beekeepers over a two-year period (2019-2020). Our objectives were: (i) establish reliable prognostic reference ranges for spore concentrations in extracted honey to determine future AFB risk at the apiary level; (ii) identify management practices as targets for mitigation of risk. P. larvae spores were detected in 753 of 1476 samples (51%). Beekeepers were stratified into low (< 2 spores/gram), moderate (2- < 100 spores/gram), and high (≥ 100 spores/gram) risk categories. Of forty-nine L beekeepers sampled in 2019, those that reported AFB in 2020 included 0/26 low, 3/18 moderate, and 3/5 high risk. Of twenty-seven L beekeepers sampled in 2020, those that reported AFB in 2021 included 0/11 low, 2/14 moderate, and 1/2 high risk. Predictive modelling included indoor overwintering of hives, purchase of used equipment, movement of honey-producing colonies between apiaries, beekeeper demographic, and antimicrobial use as risk category predictors. Saskatchewan beekeepers with fewer than 2 spores/gram in extracted honey that avoid high risk activities may be considered at low risk of AFB the following year.


Asunto(s)
Miel , Paenibacillus larvae , Paenibacillus , Animales , Abejas , Larva , Saskatchewan , Esporas Bacterianas , Estados Unidos
5.
PLoS One ; 17(2): e0263602, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35130328

RESUMEN

Three commercial honey bee operations in Saskatchewan, Canada, with outbreaks of American foulbrood (AFB) and recent or ongoing metaphylactic antibiotic use were intensively sampled to detect spores of Paenibacillus larvae during the summer of 2019. Here, we compared spore concentrations in different sample types within individual hives, assessed the surrogacy potential of honey collected from honey supers in place of brood chamber honey or adult bees within hives, and evaluated the ability of pooled, extracted honey to predict the degree of spore contamination identified through individual hive testing. Samples of honey and bees from hives within apiaries with a recent, confirmed case of AFB in a single hive (index apiaries) and apiaries without clinical evidence of AFB (unaffected apiaries), as well as pooled, apiary-level honey samples from end-of-season extraction, were collected and cultured to detect and enumerate spores. Only a few hives were heavily contaminated by spores in any given apiary. All operations were different from one another with regard to both the overall degree of spore contamination across apiaries and the distribution of spores between index apiaries and unaffected apiaries. Within operations, individual hive spore concentrations in unaffected apiaries were significantly different from index apiaries in the brood chamber (BC) honey, honey super (HS) honey, and BC bees of one of three operations. Across all operations, BC honey was best for discriminating index apiaries from unaffected apiaries (p = 0.001), followed by HS honey (p = 0.06), and BC bees (p = 0.398). HS honey positively correlated with both BC honey (rs = 0.76, p < 0.0001) and bees (rs = 0.50, p < 0.0001) and may be useful as a surrogate for either. Spore concentrations in pooled, extracted honey seem to have predictive potential for overall spore contamination within each operation and may have prognostic value in assessing the risk of future AFB outbreaks at the apiary (or operation) level.


Asunto(s)
Abejas/microbiología , Miel/microbiología , Paenibacillus larvae/fisiología , Esporas Bacterianas/aislamiento & purificación , Enfermedades de los Animales/diagnóstico , Enfermedades de los Animales/epidemiología , Enfermedades de los Animales/prevención & control , Animales , Antibacterianos/uso terapéutico , Apicultura/estadística & datos numéricos , Colapso de Colonias/microbiología , Colapso de Colonias/prevención & control , Brotes de Enfermedades , Análisis de los Alimentos , Infecciones por Bacterias Grampositivas/diagnóstico , Infecciones por Bacterias Grampositivas/epidemiología , Infecciones por Bacterias Grampositivas/prevención & control , Miel/análisis , Paenibacillus larvae/aislamiento & purificación , Saskatchewan/epidemiología , Estaciones del Año
6.
Health Expect ; 25(2): 744-753, 2022 04.
Artículo en Inglés | MEDLINE | ID: mdl-35023267

RESUMEN

INTRODUCTION: The COVID-19 pandemic has had an impact on all aspects of the health system. Little is known about how the activities and experiences of patient, family and caregiver partners, as a large group across a variety of settings within the health system, changed due to the substantial health system shifts catalysed by the pandemic. This paper reports on the results of a survey that included questions about this topic. METHODS: Canadian patient, family and caregiver partners were invited to participate in an online anonymous survey in the Fall of 2020. A virtual snowballing approach to recruitment was used. Survey invitations were shared on social media and emailed to health system and governmental organizations with the request that they share the survey with patient partners. This paper focuses on responses to two questions related to patient partner experiences during the COVID-19 pandemic. RESULTS: The COVID-19 questions were completed by 533 respondents. Over three quarters of respondents (77.9%, n = 415) indicated their patient engagement activities had been impacted by COVID-19. The majority (62.5%, n = 230) experienced at least a temporary or partial reduction in their patient engagement activities. Some respondents did see increases in their patient engagement activities (11.4%, n = 42). Many respondents provided insights into their experience with virtual platforms for engagement (n = 194), most expressed negative or mixed experiences with this shift. CONCLUSIONS: This study provides a snapshot of Canadian patient, family and caregiver partners' perspectives on the impact of COVID-19 on their engagement activities. Understanding how engagement unfolded during a crisis is critical for our future planning if patient engagement is to be fully integrated into the health system. Identifying how patient partners were engaged and not engaged during this time period, as well as the benefits and challenges of virtual engagement opportunities, offers instructive lessons for sustaining patient engagement, including the supports needed to engage with a more diverse set of patient, family and caregiver partners. PATIENT CONTRIBUTION: Patient partners were important members of the Canadian Patient Partner Study research team. They were engaged from the outset, participating in all stages of the research project. Additional patient partners were engaged to develop and pilot test the survey, and all survey respondents were patient, family or caregiver partners. The manuscript is coauthored by two patient partners.


Asunto(s)
COVID-19 , Canadá , Cuidadores , Humanos , Pandemias , Participación del Paciente , Encuestas y Cuestionarios
7.
BMJ Open ; 12(9): e061465, 2022 09 07.
Artículo en Inglés | MEDLINE | ID: mdl-36691178

RESUMEN

OBJECTIVES: To examine the sociodemographic characteristics, activities, motivations, experiences, skills and challenges of patient partners working across multiple health system settings in Canada. DESIGN: Online cross-sectional survey of self-identified patient partners. SETTING: Patient partners in multiple jurisdictions and health system organisations. PARTICIPANTS: 603 patient partners who had drawn on their experiences with the health system as a patient, family member or informal caregiver to try to improve it in some way, through their involvement in the activities of a group, organisation or government. RESULTS: Survey respondents predominantly identified as female (76.6%), white (84%) and university educated (70.2%) but were a heterogeneous group in the scope (activities and organisations), intensity (number of hours) and longevity (number of years) of their role. Primary motivations for becoming a patient partner were the desire to improve the health system based on either a negative (36.2%) or positive (23.3%) experience. Respondents reported feeling enthusiastic (83.6%), valued (76.9%) and needed (63.3%) always or most of the time; just under half felt they had always or often been adequately compensated in their role. Knowledge of the health system and the organisation they partner with are key skills needed. Two-thirds faced barriers in their role with over half identifying power imbalances. Less than half were able to see how their input was reflected in decisions or changes always or most of the time, and 40.3% had thought about quitting. CONCLUSIONS: This survey is the first of its kind to examine at a population level, the characteristics, experiences and dynamics of a large sample of self-identified patient partners. Patient partners in this sample are a sociodemographically homogenous group, yet heterogeneous in the scope, intensity and longevity of roles. Our findings provide key insights at a critical time, to inform the future of patient partnership in health systems.


Asunto(s)
Familia , Pacientes , Humanos , Femenino , Estudios Transversales , Canadá , Solución de Problemas
8.
Can Vet J ; 61(10): 1055-1059, 2020 10.
Artículo en Inglés | MEDLINE | ID: mdl-33012819

RESUMEN

Four outbreaks of American foulbrood were investigated in honey-bee operations in Saskatchewan during the summer of 2019. Clinical signs were confirmed by the Saskatchewan Provincial Specialist in Apiculture and the causative agent was cultured and identified through matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). Evaluation of management practices revealed off-label metaphylactic use of oxytetracycline in 3 of 4 operations and a discontinuation of antibiotic use in the fourth. Recent regulatory changes regarding access to medically important antimicrobials has provided an opportunity for veterinarians to promote evidence-based use of antimicrobials in apiculture while safe-guarding the health of commercial honeybee populations and the economic viability of their producers.


Enquête sur des poussées de cas cliniques de loque américaine dans des opérations d'abeilles mellifères en Saskatchewan. Quatre poussées de cas de loque américaine furent investiguées dans des opérations d'abeilles mellifères en Saskatchewan durant l'été 2019. Les signes cliniques furent confirmés par le Spécialiste provincial en apiculture de la Saskatchewan et l'agent causal fut cultivé et identifié par spectroscopie de masse par ionisation laser assistée par une matrice et analyse à temps de vol (MALDI-TOF MS). Une évaluation des pratiques de gestion a révélé l'utilisation métaphylactique en dérogation d'oxytétracycline dans trois des quatre opérations et un arrêt de l'utilisation d'antibiotique dans la quatrième. Des changements réglementaires récents concernant l'accès à des antimicrobiens importants médicalement ont fourni une opportunité aux vétérinaires de faire la promotion de l'utilisation factuelle des antimicrobiens en apiculture tout en conservant la santé des populations d'abeilles mellifères et la viabilité économique des apiculteurs.(Traduit par Dr Serge Messier).


Asunto(s)
Antiinfecciosos , Miel , Animales , Abejas , Brotes de Enfermedades/veterinaria , Saskatchewan/epidemiología , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/veterinaria , Estados Unidos
9.
Gates Open Res ; 3: 1547, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31667465

RESUMEN

Background: The wMel strain of Wolbachia has been successfully introduced into Aedes aegypti mosquitoes and subsequently shown in laboratory studies to reduce transmission of a range of viruses including dengue, Zika, chikungunya, yellow fever, and Mayaro viruses that cause human disease. Here we report the entomological and epidemiological outcomes of staged deployment of Wolbachia across nearly all significant dengue transmission risk areas in Australia. Methods: The  wMel strain of  Wolbachia was backcrossed into the local  Aedes aegypti genotype (Cairns and Townsville backgrounds) and mosquitoes were released in the field by staff or via community assisted methods. Mosquito monitoring was undertaken and mosquitoes were screened for the presence of  Wolbachia. Dengue case notifications were used to track dengue incidence in each location before and after releases. Results: Empirical analyses of the Wolbachia mosquito releases, including data on the density, frequency and duration of Wolbachia mosquito releases, indicate that Wolbachia can be readily established in local mosquito populations, using a variety of deployment options and over short release durations (mean release period 11 weeks, range 2-22 weeks). Importantly, Wolbachia frequencies have remained stable in mosquito populations since releases for up to 8 years. Analysis of dengue case notifications data demonstrates near-elimination of local dengue transmission for the past five years in locations where Wolbachia has been established. The regression model estimate of Wolbachia intervention effect from interrupted time series analyses of case notifications data prior to and after releases, indicated a 96% reduction in dengue incidence in Wolbachia treated populations (95% confidence interval: 84 - 99%). Conclusion: Deployment of the wMel strain of Wolbachia into local Ae. aegypti populations across the Australian regional cities of Cairns and most smaller regional communities with a past history of dengue has resulted in the reduction of local dengue transmission across all deployment areas.

10.
Gates Open Res ; 2: 36, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-30596205

RESUMEN

Background: A number of new technologies are under development for the control of mosquito transmitted viruses, such as dengue, chikungunya and Zika that all require the release of modified mosquitoes into the environment. None of these technologies has been able to demonstrate evidence that they can be implemented at a scale beyond small pilots. Here we report the first successful citywide scaled deployment of Wolbachia in the northern Australian city of Townsville. Methods: The wMel strain of Wolbachia was backcrossed into a local Aedes aegypti genotype and mass reared mosquitoes were deployed as eggs using mosquito release containers (MRCs). In initial stages these releases were undertaken by program staff but in later stages this was replaced by direct community release including the development of a school program that saw children undertake releases. Mosquito monitoring was undertaken with Biogents Sentinel (BGS) traps and individual mosquitoes were screened for the presence of Wolbachia with a Taqman qPCR or LAMP diagnostic assay. Dengue case notifications from Queensland Health Communicable Disease Branch were used to track dengue cases in the city before and after release. Results: Wolbachia was successfully established into local Ae. aegypti mosquitoes across 66 km 2 in four stages over 28 months with full community support.  A feature of the program was the development of a scaled approach to community engagement. Wolbachia frequencies have remained stable since deployment and to date no local dengue transmission has been confirmed in any area of Townsville after Wolbachia has established, despite local transmission events every year for the prior 13 years and an epidemiological context of increasing imported cases. Conclusion: Deployment of Wolbachia into Ae. aegypti populations can be readily scaled to areas of ~60km 2 quickly and cost effectively and appears in this context to be effective at stopping local dengue transmission.

11.
J Environ Manage ; 169: 155-66, 2016 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-26741563

RESUMEN

The temporal speeds and spatial scales at which ecosystem processes operate are often at odds with the scale and speed at which natural resources such as soil, water and vegetation are managed those. Scale mismatches often occur as a result of the time-lag between policy development, implementation and observable changes in natural capital in particular. In this study, we analyse some of the transformations that can occur in complex forest-shrubland socio-ecological systems undergoing biophysical and socioeconomic change. We use a Multiway Factor Analysis (MFA) applied to a representative set of variables to assess changes in components of natural, economic and social capitals over time. Our results indicate similarities among variables and spatial units (i.e. municipalities) which allows us to rank the variables used to describe the SES according to their rapidity of change. The novelty of the proposed framework lies in the fact that the assessment of rapidity-to-change, based on the MFA, takes into account the multivariate relationships among the system's variables, identifying the net rate of change for the whole system, and the relative impact that individual variables exert on the system itself. The aim of this study was to assess the influence of fast and slow variables on the evolution of socio-economic systems based on simplified multivariate procedures applicable to vastly different socio-economic contexts and conditions. This study also contributes to quantitative analysis methods for long-established socio-ecological systems, which may help in designing more effective, and sustainable land management strategies in environmentally sensitive areas.


Asunto(s)
Bosques , Suelo/química , Clima , Ecosistema , Monitoreo del Ambiente , Italia
12.
Health Expect ; 19(4): 817-27, 2016 08.
Artículo en Inglés | MEDLINE | ID: mdl-26113295

RESUMEN

OBJECTIVES: Only rudimentary tools exist to support health system organizations to evaluate their public and patient engagement (PPE) activities. This study responds to this gap by developing a generic evaluation tool for use in a wide range of organizations. METHODS: The evaluation tool was developed through an iterative, collaborative process informed by a review of published and grey literature and with the input of Canadian PPE researchers and practitioners. Over a 3-year period, structured e-mail, telephone and face-to-face exchanges, including a modified Delphi process, were used to produce an evaluation tool that includes core principles of high-quality engagement, expected outcomes for each principle and three unique evaluation questionnaires that were tested and revised with input from 65 end users. RESULTS: The tool is structured around four core principles of 'quality engagement': (i) integrity of design and process; (ii) influence and impact; (iii) participatory culture; and (iv) collaboration and common purpose. Three unique questionnaires were developed to assess each of these four evaluation domains from the following perspectives: (i) those who participate in PPE activities; (ii) those who plan, execute or sponsor PPE activities within organizations; and (iii) those who provide the leadership and capacity for PPE within their organizations. CONCLUSIONS: This is the first known collaboration of researchers and practitioners in the co-design of a comprehensive PPE evaluation tool aimed at three distinct respondent groups and for use in a wide range of health system organization settings.


Asunto(s)
Sector de Atención de Salud , Planificación en Salud , Participación del Paciente , Canadá , Técnica Delfos , Política de Salud , Prioridades en Salud , Humanos , Evaluación de Necesidades , Formulación de Políticas , Encuestas y Cuestionarios
13.
Artículo en Inglés | MEDLINE | ID: mdl-26027879

RESUMEN

Early and accurate diagnosis of stable coronary artery disease (CAD) is crucial to reduce morbidity, mortality and healthcare costs. This critical appraisal of health-economic literature concerning non-invasive diagnostic cardiac imaging aims to summarize current approaches to economic evaluation of diagnostic cardiac imaging and associated procedural risks, inform cardiologists how to use economic analyses for decision-making, highlight areas where new information could strengthen the economic evaluation and shed light on cost-effective approaches to diagnose stable CAD. Economic analysis can support cardiologists' decision-making. Current economic evidence in the field does not provide sufficient information to guide the choice among different imaging modalities or strategies for each patient. Available economic analyses suggest that computed tomography coronary angiography (CTCA) is a cost-effective approach to rule out CAD prior to invasive coronary angiography in patients with low to intermediate pre-test probability of disease and that stress imaging modalities may be cost-effective at variable pre-test probabilities.


Asunto(s)
Angiografía Coronaria/métodos , Enfermedad de la Arteria Coronaria/diagnóstico , Tomografía Computarizada por Rayos X/métodos , Angiografía Coronaria/economía , Enfermedad de la Arteria Coronaria/economía , Análisis Costo-Beneficio , Toma de Decisiones , Humanos , Tomografía Computarizada por Rayos X/economía
16.
Contemp Nurse ; 20(2): 221-33, 2005 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-16393104

RESUMEN

Males in nursing undoubtedly represent a minority group. However there have been relatively few studies which have investigated their unique experiences, compared with women in male dominated professions. This study conducted in an undergraduate nursing program, analysed the experience of males in nursing regarding (1) decision to enter the profession, during the course, both academic and clinical and (2) methods appropriate for recruiting more males to the profession. In general the results indicate overall positive acceptance of males in nursing, but several factors explored, indicate that change is essential if males are to remain and flourish in the profession.


Asunto(s)
Actitud , Selección de Profesión , Educación en Enfermería , Enfermeros/provisión & distribución , Estudiantes de Enfermería/psicología , Adulto , Australia , Humanos , Entrevistas como Asunto , Masculino , Enfermeros/psicología
18.
Nucleic Acids Res ; 31(11): 2803-10, 2003 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-12771207

RESUMEN

We have cloned the M and S genes of the restriction-modification (R-M) system AhdI and have purified the resulting methyltransferase to homogeneity. M.AhdI is found to form a 170 kDa tetrameric enzyme having a subunit stoichiometry M2S2 (where the M and S subunits are responsible for methylation and DNA sequence specificity, respectively). Sedimentation equilibrium experiments show that the tetrameric enzyme dissociates to form a heterodimer at low concentration, with K(d) approximately 2 microM. The intact (tetrameric) enzyme binds specifically to a 30 bp DNA duplex containing the AhdI recognition sequence GACN5GTC with high affinity (K(d) approximately 50 nM), but at low enzyme concentration the DNA binding activity is governed by the dissociation of the tetramer into dimers, leading to a sigmoidal DNA binding curve. In contrast, only non-specific binding is observed if the duplex lacks the recognition sequence. Methylation activity of the purified enzyme was assessed by its ability to prevent restriction by the cognate endonuclease. The subunit structure of the M.AhdI methyltransferase resembles that of type I MTases, in contrast to the R.AhdI endonuclease which is typical of type II systems. AhdI appears to be a novel R-M system with properties intermediate between simple type II systems and more complex type I systems, and may represent an intermediate in the evolution of R-M systems.


Asunto(s)
Metilasas de Modificación del ADN/química , Metilasas de Modificación del ADN/metabolismo , Secuencia de Aminoácidos , Sitios de Unión , Clonación Molecular , Secuencia de Consenso , ADN/metabolismo , Metilasas de Modificación del ADN/aislamiento & purificación , Dimerización , Escherichia coli/enzimología , Genes Bacterianos , Modelos Moleculares , Datos de Secuencia Molecular , Subunidades de Proteína , Alineación de Secuencia , Ultracentrifugación
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