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Jiang JH, Cameron DR, Nethercott C, Aires-de-Sousa M, Peleg AY. Virulence attributes of successful methicillin-resistant Staphylococcus aureus lineages. Clin Microbiol Rev 2023; 36:e0014822. [PMID: 37982596 PMCID: PMC10732075 DOI: 10.1128/cmr.00148-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2023] Open
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of severe and often fatal infections. MRSA epidemics have occurred in waves, whereby a previously successful lineage has been replaced by a more fit and better adapted lineage. Selection pressures in both hospital and community settings are not uniform across the globe, which has resulted in geographically distinct epidemiology. This review focuses on the mechanisms that trigger the establishment and maintenance of current, dominant MRSA lineages across the globe. While the important role of antibiotic resistance will be mentioned throughout, factors which influence the capacity of S. aureus to colonize and cause disease within a host will be the primary focus of this review. We show that while MRSA possesses a diverse arsenal of toxins including alpha-toxin, the success of a lineage involves more than just producing toxins that damage the host. Success is often attributed to the acquisition or loss of genetic elements involved in colonization and niche adaptation such as the arginine catabolic mobile element, as well as the activity of regulatory systems, and shift metabolism accordingly (e.g., the accessory genome regulator, agr). Understanding exactly how specific MRSA clones cause prolonged epidemics may reveal targets for therapies, whereby both core (e.g., the alpha toxin) and acquired virulence factors (e.g., the Panton-Valentine leukocidin) may be nullified using anti-virulence strategies.
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Affiliation(s)
- Jhih-Hang Jiang
- Department of Microbiology, Infection Program, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
- Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia
| | - David R. Cameron
- Department of Biomedical Research, University of Bern, Bern, Switzerland
| | - Cara Nethercott
- Department of Microbiology, Infection Program, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
| | - Marta Aires-de-Sousa
- Laboratory of Molecular Genetics, Institutode Tecnologia Químicae Biológica António Xavier (ITQB-NOVA), Universidade Nova de Lisboa, Oeiras, Portugal
- Escola Superior de Saúde da Cruz Vermelha Portuguesa-Lisboa (ESSCVP-Lisboa), Lisbon, Portugal
| | - Anton Y. Peleg
- Department of Microbiology, Infection Program, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
- Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia
- Centre to Impact Antimicrobial Resistance, Monash University, Clayton, Melbourne, Victoria, Australia
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Pitton M, Valente LG, Oberhaensli S, Casanova C, Sendi P, Schnegg B, Jakob SM, Cameron DR, Que YA, Fürholz M. Dynamics of bacterial pathogens at the driveline exit site in patients with ventricular assist devices: A prospective, observational, single-center cohort study. J Heart Lung Transplant 2023; 42:1445-1454. [PMID: 37245557 DOI: 10.1016/j.healun.2023.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 03/30/2023] [Accepted: 05/24/2023] [Indexed: 05/30/2023] Open
Abstract
BACKGROUND Driveline infections (DLIs) at the exit site are frequent in patients with left ventricular assist devices (LVADs). The dynamics from colonization to infection are yet to be investigated. We combined systematic swabbing at the driveline exit site and genomic analyses to study the dynamics of bacterial pathogens and get insights into DLIs pathogenesis. METHODS A prospective, observational, single-center cohort study at the University Hospital of Bern, Switzerland was performed. Patients with LVAD were systematically swabbed at the driveline exit site between June 2019 and December 2021, irrespective of signs and symptoms of DLI. Bacterial isolates were identified and a subset was whole-genome sequenced. RESULTS Fifty-three patients were screened, of which 45 (84.9%) were included in the final population. Bacterial colonization at the driveline exit site without manifestation of DLI was frequent and observed in 17 patients (37.8%). Twenty-two patients (48.9%) developed at least one DLI episode over the study period. Incidence of DLIs reached 2.3 cases per 1000 LVAD days. The majority of the organisms cultivated from exit sites were Staphylococcus species. Genome analysis revealed that bacteria persisted at the driveline exit site over time. In four patients, transition from colonization to clinical DLI was observed. CONCLUSIONS Our study is the first to address bacterial colonization in the LVAD-DLI setting. We observed that bacterial colonization at the driveline exit site was a frequent phenomenon, and in a few cases, it preceded clinically relevant infections. We also provided acquisition of hospital-acquired multidrug-resistant bacteria and the transmission of pathogens between patients.
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Affiliation(s)
- Melissa Pitton
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences (GCB), University of Bern, Bern, Switzerland
| | - Luca G Valente
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences (GCB), University of Bern, Bern, Switzerland; Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Simone Oberhaensli
- Interfaculty Bioinformatics Unit, University of Bern, Bern, Switzerland; SIB Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Carlo Casanova
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Parham Sendi
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Bruno Schnegg
- Department of Cardiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Stephan M Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - David R Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Yok-Ai Que
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Monika Fürholz
- Department of Cardiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
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Nowakowska J, Cameron DR, De Martino A, Kühn J, Le Fresne-Languille S, Leuillet S, Amouzou Y, Wittke F, Carton T, Le Vacon F, Chaves RL, Nicolas-Metral V, Vuagniaux G. Evaluation of the microbiota-sparing properties of the anti-staphylococcal antibiotic afabicin. J Antimicrob Chemother 2023:7192828. [PMID: 37294305 PMCID: PMC10393889 DOI: 10.1093/jac/dkad181] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Accepted: 05/23/2023] [Indexed: 06/10/2023] Open
Abstract
BACKGROUND Antibiotic use is associated with collateral damage to the healthy microbiota. Afabicin is a first-in-class prodrug inhibitor of the FabI enzyme that, when converted to the pharmacologically active agent afabicin desphosphono, demonstrates a staphylococcal-specific spectrum of activity. An expected benefit of highly targeted antibiotics such as afabicin is microbiome preservation. OBJECTIVES To compare the effects of oral treatment with afabicin and standard-of-care antibiotics upon the murine gut microbiota, and to assess the effects of oral afabicin treatment on the human gut microbiota. METHODS Gut microbiota effects of a 10 day oral course of afabicin treatment were monitored in mice and compared with clindamycin, linezolid and moxifloxacin at human-equivalent dose levels using 16S rDNA sequencing. Further, the gut microbiota of healthy volunteers was longitudinally assessed across 20 days of oral treatment with afabicin 240 mg twice daily. RESULTS Afabicin treatment did not significantly alter gut microbiota diversity (Shannon H index) or richness (rarefied Chao1) in mice. Only limited changes to taxonomic abundances were observed in afabicin-treated animals. In contrast, clindamycin, linezolid and moxifloxacin each caused extensive dysbiosis in the murine model. In humans, afabicin treatment was not associated with alterations in Shannon H or rarefied Chao1 indices, nor relative taxonomic abundances, supporting the findings from the animal model. CONCLUSIONS Oral treatment with afabicin is associated with preservation of the gut microbiota in mice and healthy subjects.
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Affiliation(s)
- J Nowakowska
- Translational Medicine Department, Debiopharm International SA, Chemin Messidor 5-7, 1006 Lausanne, Switzerland
| | - D R Cameron
- Translational Medicine Department, Debiopharm International SA, Chemin Messidor 5-7, 1006 Lausanne, Switzerland
| | - A De Martino
- Research and Development Department, Biofortis SAS, 3 route de la Chatterie, 44800 Saint-Herblain, France
| | - J Kühn
- Translational Medicine Department, Debiopharm International SA, Chemin Messidor 5-7, 1006 Lausanne, Switzerland
| | - S Le Fresne-Languille
- Research and Development Department, Biofortis SAS, 3 route de la Chatterie, 44800 Saint-Herblain, France
| | - S Leuillet
- Research and Development Department, Biofortis SAS, 3 route de la Chatterie, 44800 Saint-Herblain, France
| | - Y Amouzou
- Research and Development Department, Biofortis SAS, 3 route de la Chatterie, 44800 Saint-Herblain, France
| | - F Wittke
- Clinical Development Department, Debiopharm International SA, Chemin Messidor 5-7, 1006 Lausanne, Switzerland
| | - T Carton
- Research and Development Department, Biofortis SAS, 3 route de la Chatterie, 44800 Saint-Herblain, France
| | - F Le Vacon
- Research and Development Department, Biofortis SAS, 3 route de la Chatterie, 44800 Saint-Herblain, France
| | - R L Chaves
- Clinical Development Department, Debiopharm International SA, Chemin Messidor 5-7, 1006 Lausanne, Switzerland
| | - V Nicolas-Metral
- Translational Medicine Department, Debiopharm International SA, Chemin Messidor 5-7, 1006 Lausanne, Switzerland
| | - G Vuagniaux
- Translational Medicine Department, Debiopharm International SA, Chemin Messidor 5-7, 1006 Lausanne, Switzerland
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Cameron DR, Pitton M, Oberhaensli S, Schlegel K, Prod’hom G, Blanc DS, Jakob SM, Que YA. Parallel Evolution of Pseudomonas aeruginosa during a Prolonged ICU-Infection Outbreak. Microbiol Spectr 2022; 10:e0274322. [PMID: 36342287 PMCID: PMC9769503 DOI: 10.1128/spectrum.02743-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 10/19/2022] [Indexed: 11/09/2022] Open
Abstract
Most knowledge about Pseudomonas aeruginosa pathoadaptation is derived from studies on airway colonization in cystic fibrosis; little is known about adaptation in acute settings. P. aeruginosa frequently affects burned patients and the burn wound niche has distinct properties that likely influence pathoadaptation. This study aimed to genetically and phenotypically characterize P. aeruginosa isolates collected during an outbreak of infection in a burn intensive care unit (ICU). Sequencing reads from 58 isolates of ST1076 P. aeruginosa taken from 23 patients were independently mapped to a complete reference genome for the lineage (H25338); genetic differences were identified and were used to define the population structure. Comparative genomic analysis at single-nucleotide resolution identified pathoadaptive genes that evolved multiple, independent mutations. Three key phenotypic assays (growth performance, motility, carbapenem resistance) were performed to complement the genetic analysis for 47 unique isolates. Population structure for the ST1076 lineage revealed 11 evolutionary sublineages. Fifteen pathoadaptive genes evolved mutations in at least two sublineages. The most prominent functional classes affected were transcription/two-component regulatory systems, and chemotaxis/motility and attachment. The most frequently mutated gene was oprD, which codes for outer membrane porin involved in uptake of carbapenems. Reduced growth performance and motility were found to be adaptive phenotypic traits, as was high level of carbapenem resistance, which correlated with higher carbapenem consumption during the outbreak. Multiple prominent linages evolved each of the three traits in parallel providing evidence that they afford a fitness advantage for P. aeruginosa in the context of human burn infection. IMPORTANCE Pseudomonas aeruginosa is a Gram-negative pathogen causing infections in acutely burned patients. The precise mechanisms required for the establishment of infection in the burn setting, and adaptive traits underpinning prolonged outbreaks are not known. We have assessed genotypic data from 58 independent P. aeruginosa isolates taken from a single lineage that was responsible for an outbreak of infection in a burn ICU that lasted for almost 2.5 years and affected 23 patients. We identified a core set of 15 genes that we predict to control pathoadaptive traits in the burn infection based on the frequency with which independent mutations evolved. We combined the genotypic data with phenotypic data (growth performance, motility, antibiotic resistance) and clinical data (antibiotic consumption) to identify adaptive phenotypes that emerged in parallel. High-level carbapenem resistance evolved rapidly, and frequently, in response to high clinical demand for this antibiotic class during the outbreak.
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Affiliation(s)
- David R. Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Melissa Pitton
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences (GCB), University of Bern, Bern, Switzerland
| | - Simone Oberhaensli
- Interfaculty Bioinformatics Unit and SIB Swiss Institute of Bioinformatics, University of Bern, Bern, Switzerland
| | - Katja Schlegel
- Institute of Psychology, University of Bern, Bern, Switzerland
| | - Guy Prod’hom
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Dominique S. Blanc
- Service of Hospital Preventive Medicine, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Stephan M. Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Yok-Ai Que
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Spano G, Buffle E, Walti LN, Mihalj M, Cameron DR, Martinelli M, Fürholz M, Que Y, Hayward C, Reineke D, Hunziker L, Schnegg B. Ten‐year retrospective cohort analysis of Ventricular Assist Device infections. Artif Organs 2022; 47:898-905. [PMID: 36478260 DOI: 10.1111/aor.14477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 11/01/2022] [Accepted: 11/22/2022] [Indexed: 12/12/2022]
Abstract
BACKGROUND The number of patients treated by ventricular assist devices (VAD) and the duration of VAD treatment is increasing. One of the main complications in terms of morbidity and mortality for VAD patients are microbial infections. With this study, we aimed to investigate the epidemiology and microbiological characteristics of infections occurring in a VAD population to identify modifiable factors. METHODS We retrospectively analyzed patient characteristics, treatments and outcomes of VAD-specific/related infections. All patients implanted in our institution with a continuous flow VAD between January 2009 and January 2019 were included. Risk factors for VAD infection were assessed using simple and multiple linear regressions. RESULTS Of the 104 patients screened, 99 were included in the analysis, the majority of which were men (78%). At implantation, the mean age was 56 years and the median time on VAD support was 541 days. The overall infection rate per year per patient was 1.4. Forty-seven patients (60%) suffered from VAD-specific/related infection. Half of all infection episodes occurred in the first 4 months but the proportion of VAD-specific/related infection was higher after the first 4 months (74% of all infection). Using regression models, no patient specific risk factors were associated with VAD-specific/related infections. CONCLUSION No predictive factors for infection during VAD support were identified in this study. By extension, diabetes, renal insufficiency, age or high BMI are not sufficient to deny a patient access to ventricular support.
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Affiliation(s)
- Giancarlo Spano
- Centre for Advanced Heart Failure, Department of Cardiology, Inselspital Bern University Hospital Bern Switzerland
| | - Eric Buffle
- Centre for Advanced Heart Failure, Department of Cardiology, Inselspital Bern University Hospital Bern Switzerland
| | - Laura Naëmi Walti
- Department of Infectious Diseases, Inselspital, Bern University Hospital University of Bern
| | - Maks Mihalj
- Department of Cardiac Surgery, Inselspital Bern University Hospital Bern Switzerland
| | - David R. Cameron
- Department of Intensive Care Medicine, Inselspital Bern University Hospital Bern Switzerland
| | - Michele Martinelli
- Centre for Advanced Heart Failure, Department of Cardiology, Inselspital Bern University Hospital Bern Switzerland
| | - Monika Fürholz
- Centre for Advanced Heart Failure, Department of Cardiology, Inselspital Bern University Hospital Bern Switzerland
| | - Yok‐Ai Que
- Department of Intensive Care Medicine, Inselspital Bern University Hospital Bern Switzerland
| | - Christopher Hayward
- Heart Failure and Transplant Unit, St Vincent's Hospital Sydney New South Wales Australia
| | - David Reineke
- Department of Infectious Diseases, Inselspital, Bern University Hospital University of Bern
| | - Lukas Hunziker
- Centre for Advanced Heart Failure, Department of Cardiology, Inselspital Bern University Hospital Bern Switzerland
| | - Bruno Schnegg
- Centre for Advanced Heart Failure, Department of Cardiology, Inselspital Bern University Hospital Bern Switzerland
- Heart Failure and Transplant Unit, St Vincent's Hospital Sydney New South Wales Australia
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Gómez-Ochoa SA, Pitton M, Valente LG, Sosa Vesga CD, Largo J, Quiroga-Centeno AC, Hernández Vargas JA, Trujillo-Cáceres SJ, Muka T, Cameron DR, Que YA. Efficacy of phage therapy in preclinical models of bacterial infection: a systematic review and meta-analysis. Lancet Microbe 2022; 3:e956-e968. [PMID: 36370748 DOI: 10.1016/s2666-5247(22)00288-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 09/14/2022] [Accepted: 09/21/2022] [Indexed: 11/11/2022]
Abstract
BACKGROUND Antimicrobial resistance of bacterial pathogens is an increasing clinical problem and alternative approaches to antibiotic chemotherapy are needed. One of these approaches is the use of lytic bacterial viruses known as phage therapy. We aimed to assess the efficacy of phage therapy in preclinical animal models of bacterial infection. METHODS In this systematic review and meta-analysis, MEDLINE/Ovid, Embase/Ovid, CINAHL/EbscoHOST, Web of Science/Wiley, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Google Scholar were searched from inception to Sept 30, 2021. Studies assessing phage efficacy in animal models were included. Only studies that assessed the efficacy of phage therapy in treating established bacterial infections in terms of survival and bacterial abundance or density were included. Studies reporting only in-vitro or ex-vivo results and those with incomplete information were excluded. Risk-of-bias assessment was performed using the Systematic Review Centre for Laboratory Animal Experimentation tool. The main endpoints were animal survival and tissue bacterial burden, which were reported using pooled odds ratios (ORs) and mean differences with random-effects models. The I2 measure and its 95% CI were also calculated. This study is registered with PROSPERO, CRD42022311309. FINDINGS Of the 5084 references screened, 124 studies fulfilled the selection criteria. Risk of bias was high for 70 (56%) of the 124 included studies; therefore, only studies classified as having a low-to-moderate risk of bias were considered for quantitative data synthesis (n=32). Phage therapy was associated with significantly improved survival at 24 h in systemic infection models (OR 0·08 [95% CI 0·03 to 0·20]; I2=55% [95% CI 8 to 77]), skin infection (OR 0·08 [0·04 to 0·19]; I2 = 0% [0 to 79]), and pneumonia models (OR 0·13 [0·06 to 0·31]; I2=0% [0 to 68]) when compared with placebo. Animals with skin infections (mean difference -2·66 [95% CI -3·17 to -2·16]; I2 = 95% [90 to 96]) and those with pneumonia (mean difference -3·35 [-6·00 to -0·69]; I2 = 99% [98 to 99]) treated with phage therapy had significantly lower tissue bacterial loads at 5 ± 2 days of follow-up compared with placebo. INTERPRETATION Phage therapy significantly improved animal survival and reduced organ bacterial loads compared with placebo in preclinical animal models. However, high heterogeneity was observed in some comparisons. More evidence is needed to identify the factors influencing phage therapy performance to improve future clinical application. FUNDING Swiss National Foundation and Swiss Heart Foundation.
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Affiliation(s)
- Sergio Alejandro Gómez-Ochoa
- Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland; Research Center, Fundación Cardiovascular de Colombia, Bucaramanga, Colombia.
| | - Melissa Pitton
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland; Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Luca G Valente
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | | | - Jorge Largo
- Internal Medicine Department, Universidad Militar Nueva Granada, Bogotá, Colombia
| | | | | | | | - Taulant Muka
- Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland; Epistudia, Bern, Switzerland
| | - David R Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Yok-Ai Que
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
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Mahnken M, Cailleret M, Collalti A, Trotta C, Biondo C, D'Andrea E, Dalmonech D, Marano G, Mäkelä A, Minunno F, Peltoniemi M, Trotsiuk V, Nadal-Sala D, Sabaté S, Vallet P, Aussenac R, Cameron DR, Bohn FJ, Grote R, Augustynczik ALD, Yousefpour R, Huber N, Bugmann H, Merganičová K, Merganic J, Valent P, Lasch-Born P, Hartig F, Vega Del Valle ID, Volkholz J, Gutsch M, Matteucci G, Krejza J, Ibrom A, Meesenburg H, Rötzer T, van der Maaten-Theunissen M, van der Maaten E, Reyer CPO. Accuracy, realism and general applicability of European forest models. Glob Chang Biol 2022; 28:6921-6943. [PMID: 36117412 DOI: 10.1111/gcb.16384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 06/01/2022] [Accepted: 06/19/2022] [Indexed: 06/15/2023]
Abstract
Forest models are instrumental for understanding and projecting the impact of climate change on forests. A considerable number of forest models have been developed in the last decades. However, few systematic and comprehensive model comparisons have been performed in Europe that combine an evaluation of modelled carbon and water fluxes and forest structure. We evaluate 13 widely used, state-of-the-art, stand-scale forest models against field measurements of forest structure and eddy-covariance data of carbon and water fluxes over multiple decades across an environmental gradient at nine typical European forest stands. We test the models' performance in three dimensions: accuracy of local predictions (agreement of modelled and observed annual data), realism of environmental responses (agreement of modelled and observed responses of daily gross primary productivity to temperature, radiation and vapour pressure deficit) and general applicability (proportion of European tree species covered). We find that multiple models are available that excel according to our three dimensions of model performance. For the accuracy of local predictions, variables related to forest structure have lower random and systematic errors than annual carbon and water flux variables. Moreover, the multi-model ensemble mean provided overall more realistic daily productivity responses to environmental drivers across all sites than any single individual model. The general applicability of the models is high, as almost all models are currently able to cover Europe's common tree species. We show that forest models complement each other in their response to environmental drivers and that there are several cases in which individual models outperform the model ensemble. Our framework provides a first step to capturing essential differences between forest models that go beyond the most commonly used accuracy of predictions. Overall, this study provides a point of reference for future model work aimed at predicting climate impacts and supporting climate mitigation and adaptation measures in forests.
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Affiliation(s)
- Mats Mahnken
- Potsdam Institute for Climate Impact Research (PIK), Leibniz Association, Potsdam, Germany
- Forest Growth and Woody Biomass Production, TU Dresden, Tharandt, Germany
| | - Maxime Cailleret
- UMR RECOVER, INRAE, Aix-Marseille University, Aix-en-Provence, France
- Forest Dynamics Unit, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
| | - Alessio Collalti
- Forest Modelling Lab, National Research Council of Italy, Institute for Agriculture and Forestry Systems in the Mediterranean (CNR-ISAFOM), Perugia, Italy
- Department of Innovation in Biological, Agro-Food and Forest Systems (DIBAF), University of Tuscia, Viterbo, Italy
- Division Impacts on Agriculture, Forests and Ecosystem Services (IAFES), Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici, Viterbo, Italy
| | - Carlo Trotta
- Department of Innovation in Biological, Agro-Food and Forest Systems (DIBAF), University of Tuscia, Viterbo, Italy
- Division Impacts on Agriculture, Forests and Ecosystem Services (IAFES), Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici, Viterbo, Italy
| | - Corrado Biondo
- Department of Innovation in Biological, Agro-Food and Forest Systems (DIBAF), University of Tuscia, Viterbo, Italy
- Division Impacts on Agriculture, Forests and Ecosystem Services (IAFES), Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici, Viterbo, Italy
| | - Ettore D'Andrea
- Forest Modelling Lab, National Research Council of Italy, Institute for Agriculture and Forestry Systems in the Mediterranean (CNR-ISAFOM), Perugia, Italy
| | - Daniela Dalmonech
- Forest Modelling Lab, National Research Council of Italy, Institute for Agriculture and Forestry Systems in the Mediterranean (CNR-ISAFOM), Perugia, Italy
| | - Gina Marano
- Forest Modelling Lab, National Research Council of Italy, Institute for Agriculture and Forestry Systems in the Mediterranean (CNR-ISAFOM), Perugia, Italy
- Department of Environmental Systems Science, Forest Ecology, Institute of Terrestrial Ecosystems, ETH Zurich, Zurich, Switzerland
| | - Annikki Mäkelä
- Department of Forest Sciences, Institute for Atmospheric and Earth System Research (INAR) and Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
| | - Francesco Minunno
- Department of Forest Sciences, Institute for Atmospheric and Earth System Research (INAR) and Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
| | | | - Volodymyr Trotsiuk
- Forest Dynamics Unit, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
| | - Daniel Nadal-Sala
- Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, Germany
- Ecology Section, Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona (UB), Barcelona, Spain
| | - Santiago Sabaté
- Ecology Section, Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona (UB), Barcelona, Spain
- CREAF (Center for Ecological Research and Forestry Applications), Cerdanyola del Vallès, Spain
| | - Patrick Vallet
- LESSEM, INRAE, Univ. Grenoble Alpes, St-Martin-d'Hères, France
| | | | - David R Cameron
- UK Centre for Ecology and Hydrology, Penicuik, Midlothian, UK
| | - Friedrich J Bohn
- Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Rüdiger Grote
- Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, Germany
| | | | - Rasoul Yousefpour
- Forestry Economics and Forest Planning, University of Freiburg, Freiburg, Germany
- Institute of Forestry and Conservation, John Daniels Faculty of Architecture, Landscape and Design, University of Toronto, Toronto, Ontario, Canada
| | - Nica Huber
- Department of Environmental Systems Science, Forest Ecology, Institute of Terrestrial Ecosystems, ETH Zurich, Zurich, Switzerland
- Remote Sensing, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
| | - Harald Bugmann
- Department of Environmental Systems Science, Forest Ecology, Institute of Terrestrial Ecosystems, ETH Zurich, Zurich, Switzerland
| | - Katarina Merganičová
- Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Praha, Czech Republic
- Department of Biodiversity of Ecosystems and Landscape, Institute of Landscape Ecology, Slovak Academy of Sciences, Nitra, Slovakia
| | - Jan Merganic
- Faculty of Forestry, Technical University in Zvolen, Zvolen, Slovak Republic
| | - Peter Valent
- Faculty of Forestry, Technical University in Zvolen, Zvolen, Slovak Republic
| | - Petra Lasch-Born
- Potsdam Institute for Climate Impact Research (PIK), Leibniz Association, Potsdam, Germany
| | - Florian Hartig
- Theoretical Ecology, University of Regensburg, Regensburg, Germany
| | | | - Jan Volkholz
- Potsdam Institute for Climate Impact Research (PIK), Leibniz Association, Potsdam, Germany
| | - Martin Gutsch
- Potsdam Institute for Climate Impact Research (PIK), Leibniz Association, Potsdam, Germany
| | - Giorgio Matteucci
- Forest Modelling Lab, National Research Council of Italy, Institute for Agriculture and Forestry Systems in the Mediterranean (CNR-ISAFOM), Perugia, Italy
| | - Jan Krejza
- Global Change Research Institute CAS, Brno, Czech Republic
- Department of Forest Ecology, Mendel University in Brno, Brno, Czech Republic
| | - Andreas Ibrom
- Department of Environmental Engineering, Technical University of Denmark (DTU), Lyngby, Denmark
| | | | - Thomas Rötzer
- Forest Growth and Yield Science, TU München, Freising, Germany
| | | | | | - Christopher P O Reyer
- Potsdam Institute for Climate Impact Research (PIK), Leibniz Association, Potsdam, Germany
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8
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Rodriguez B, Branca M, Gutt‐Will M, Roth M, Söll N, Nansoz S, Cameron DR, Tankisi H, Tan SV, Bostock H, Raabe A, Schefold JC, Jakob SM, Z'Graggen WJ. Development and early diagnosis of critical illness myopathy in COVID-19 associated acute respiratory distress syndrome. J Cachexia Sarcopenia Muscle 2022; 13:1883-1895. [PMID: 35384375 PMCID: PMC9088321 DOI: 10.1002/jcsm.12989] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 12/02/2021] [Accepted: 03/07/2022] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND The COVID-19 pandemic has greatly increased the incidence and clinical importance of critical illness myopathy (CIM), because it is one of the most common complications of modern intensive care medicine. Current diagnostic criteria only allow diagnosis of CIM at an advanced stage, so that patients are at risk of being overlooked, especially in early stages. To determine the frequency of CIM and to assess a recently proposed tool for early diagnosis, we have followed a cohort of COVID-19 patients with acute respiratory distress syndrome and compared the time course of muscle excitability measurements with the definite diagnosis of CIM. METHODS Adult COVID-19 patients admitted to the Intensive Care Unit of the University Hospital Bern, Switzerland requiring mechanical ventilation were recruited and examined on Days 1, 2, 5, and 10 post-intubation. Clinical examination, muscle excitability measurements, medication record, and laboratory analyses were performed on all study visits, and additionally nerve conduction studies, electromyography and muscle biopsy on Day 10. Muscle excitability data were compared with a cohort of 31 age-matched healthy subjects. Diagnosis of definite CIM was made according to the current guidelines and was based on patient history, results of clinical and electrophysiological examinations as well as muscle biopsy. RESULTS Complete data were available in 31 out of 44 recruited patients (mean [SD] age, 62.4 [9.8] years). Of these, 17 (55%) developed CIM. Muscle excitability measurements on Day 10 discriminated between patients who developed CIM and those who did not, with a diagnostic precision of 90% (AUC 0.908; 95% CI 0.799-1.000; sensitivity 1.000; specificity 0.714). On Days 1 and 2, muscle excitability parameters also discriminated between the two groups with 73% (AUC 0.734; 95% CI 0.550-0.919; sensitivity 0.562; specificity 0.857) and 82% (AUC 0.820; CI 0.652-0.903; sensitivity 0.750; specificity 0.923) diagnostic precision, respectively. All critically ill COVID-19 patients showed signs of muscle membrane depolarization compared with healthy subjects, but in patients who developed CIM muscle membrane depolarization on Days 1, 2 and 10 was more pronounced than in patients who did not develop CIM. CONCLUSIONS This study reports a 55% prevalence of definite CIM in critically ill COVID-19 patients. Furthermore, the results confirm that muscle excitability measurements may serve as an alternative method for CIM diagnosis and support its use as a tool for early diagnosis and monitoring the development of CIM.
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Affiliation(s)
- Belén Rodriguez
- Department of Neurosurgery, Inselspital, Bern University HospitalUniversity of BernBernSwitzerland
| | | | - Marielena Gutt‐Will
- Department of Neurosurgery, Inselspital, Bern University HospitalUniversity of BernBernSwitzerland
| | - Marianne Roth
- Department of Intensive Care Medicine, Inselspital, Bern University HospitalUniversity of BernBernSwitzerland
| | - Nicole Söll
- Department of Neurosurgery, Inselspital, Bern University HospitalUniversity of BernBernSwitzerland
| | - Sandra Nansoz
- Department of Intensive Care Medicine, Inselspital, Bern University HospitalUniversity of BernBernSwitzerland
| | - David R. Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University HospitalUniversity of BernBernSwitzerland
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital & Dept of Clinical MedicineAarhus UniversityAarhusDenmark
| | - S. Veronica Tan
- MRC Centre for Neuromuscular DiseasesUCL Institute of Neurology, The National Hospital for Neurology and NeurosurgeryLondonUK
| | - Hugh Bostock
- Department of Neuromuscular DiseasesUCL Queen Square Institute of NeurologyLondonUK
| | - Andreas Raabe
- Department of Neurosurgery, Inselspital, Bern University HospitalUniversity of BernBernSwitzerland
| | - Joerg C. Schefold
- Department of Intensive Care Medicine, Inselspital, Bern University HospitalUniversity of BernBernSwitzerland
| | - Stephan M. Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University HospitalUniversity of BernBernSwitzerland
| | - Werner J. Z'Graggen
- Department of Neurosurgery, Inselspital, Bern University HospitalUniversity of BernBernSwitzerland
- Department of Neurology, InselspitalBern University Hospital, University of BernBernSwitzerland
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9
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Valente LG, Le ND, Pitton M, Chiffi G, Grandgirard D, Jakob SM, Cameron DR, Resch G, Que YA, Leib SL. Efficacy assessment of a novel endolysin PlyAZ3aT for the treatment of ceftriaxone-resistant pneumococcal meningitis in an infant rat model. PLoS One 2022; 17:e0266928. [PMID: 35472061 PMCID: PMC9041855 DOI: 10.1371/journal.pone.0266928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 03/29/2022] [Indexed: 11/21/2022] Open
Abstract
Background Treatment failure in pneumococcal meningitis due to antibiotic resistance is an increasing clinical challenge and alternatives to antibiotics warrant investigation. Phage-derived endolysins efficiently kill gram-positive bacteria including multi-drug resistant strains, making them attractive therapeutic candidates. The current study assessed the therapeutic potential of the novel endolysin PlyAZ3aT in an infant rat model of ceftriaxone-resistant pneumococcal meningitis. Methods Efficacy of PlyAZ3aT was assessed in a randomized, blinded and controlled experimental study in infant Wistar rats. Meningitis was induced by intracisternal infection with 5 x 107 CFU/ml of a ceftriaxone-resistant clinical strain of S. pneumoniae, serotype 19A. Seventeen hours post infection (hpi), animals were randomized into 3 treatment groups and received either (i) placebo (phosphate buffered saline [PBS], n = 8), (ii) 50 mg/kg vancomycin (n = 10) or (iii) 400 mg/kg PlyAZ3aT (n = 8) via intraperitoneal injection. Treatments were repeated after 12 h. Survival at 42 hpi was the primary outcome; bacterial loads in cerebrospinal fluid (CSF) and blood were secondary outcomes. Additionally, pharmacokinetics of PlyAZ3aT in serum and CSF was assessed. Results PlyAZ3aT did not improve survival compared to PBS, while survival for vancomycin treated animals was 70% which is a significant improvement when compared to PBS or PlyAZ3aT (p<0.05 each). PlyAZ3aT was not able to control the infection, reflected by the inability to reduce bacterial loads in the CSF, whereas Vancomycin sterilized the CSF and within 25 h. Pharmacokinetic studies indicated that PlyAZ3aT did not cross the blood brain barrier (BBB). In support, PlyAZ3aT showed a peak concentration of 785 μg/ml in serum 2 h after intraperitoneal injection but could not be detected in CSF. Conclusion In experimental pneumococcal meningitis, PlyAZ3aT failed to cure the infection due to an inability to reach the CSF. Optimization of the galenic formulation e.g. using liposomes might enable crossing of the BBB and improve treatment efficacy.
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Affiliation(s)
- Luca G. Valente
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Ngoc Dung Le
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Melissa Pitton
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Gabriele Chiffi
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Denis Grandgirard
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Stephan M. Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - David R. Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Grégory Resch
- Centre for Research and Innovation in Clinical Pharmaceutical Sciences, Lausanne University Hospital, Lausanne, Switzerland
| | - Yok-Ai Que
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Stephen L. Leib
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
- * E-mail:
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10
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Valente LG, Federer L, Iten M, Grandgirard D, Leib SL, Jakob SM, Haenggi M, Cameron DR, Que YA, Prazak J. Searching for synergy: combining systemic daptomycin treatment with localised phage therapy for the treatment of experimental pneumonia due to MRSA. BMC Res Notes 2021; 14:381. [PMID: 34579784 PMCID: PMC8474762 DOI: 10.1186/s13104-021-05796-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 09/20/2021] [Indexed: 11/24/2022] Open
Abstract
Objective Bacteriophages (or phages) are viruses which infect and lyse bacteria. The therapeutic use of phages (phage therapy) has regained attention in the last decades as an alternative strategy to treat infections caused by antimicrobial-resistant bacteria. In clinical settings it is most likely that phages are administered adjunct to antibiotics. For successful phage therapy it is therefore crucial to investigate different phage-antibiotic combinations in vivo. This study aimed to elucidate the combinatorial effects of systemic daptomycin and nebulised bacteriophages for the treatment of experimental pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA). Results Using a rat model of ventilator-associated pneumonia caused by MRSA, the simultaneous application of intravenous daptomycin and nebulised phages was not superior to aerophage therapy alone at improving animal survival (55% vs. 50%), or reducing bacterial burdens in the lungs, or spleen. Thus, this combination does not seem to be of benefit for use in patients with MRSA pneumonia.
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Affiliation(s)
- Luca G Valente
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, 3010, Bern, Switzerland.,Institute for Infectious Diseases, University of Bern, Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Lea Federer
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, 3010, Bern, Switzerland
| | - Manuela Iten
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, 3010, Bern, Switzerland
| | - Denis Grandgirard
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Stephen L Leib
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Stephan M Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, 3010, Bern, Switzerland
| | - Matthias Haenggi
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, 3010, Bern, Switzerland
| | - David R Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, 3010, Bern, Switzerland.,Department of Biomedical Research, University of Bern, Bern, Switzerland
| | - Yok-Ai Que
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, 3010, Bern, Switzerland.,Department of Biomedical Research, University of Bern, Bern, Switzerland
| | - Josef Prazak
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, 3010, Bern, Switzerland.
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11
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Oberpriller J, Cameron DR, Dietze MC, Hartig F. Towards robust statistical inference for complex computer models. Ecol Lett 2021; 24:1251-1261. [PMID: 33783944 DOI: 10.1111/ele.13728] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 10/16/2020] [Accepted: 02/11/2021] [Indexed: 01/08/2023]
Abstract
Ecologists increasingly rely on complex computer simulations to forecast ecological systems. To make such forecasts precise, uncertainties in model parameters and structure must be reduced and correctly propagated to model outputs. Naively using standard statistical techniques for this task, however, can lead to bias and underestimation of uncertainties in parameters and predictions. Here, we explain why these problems occur and propose a framework for robust inference with complex computer simulations. After having identified that model error is more consequential in complex computer simulations, due to their more pronounced nonlinearity and interconnectedness, we discuss as possible solutions data rebalancing and adding bias corrections on model outputs or processes during or after the calibration procedure. We illustrate the methods in a case study, using a dynamic vegetation model. We conclude that developing better methods for robust inference of complex computer simulations is vital for generating reliable predictions of ecosystem responses.
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Affiliation(s)
- Johannes Oberpriller
- Theoretical Ecology, University of Regensburg, Universitätsstraße 31, Regensburg, 93053, Germany
| | - David R Cameron
- UK Centre for Ecology & Hydrology, Bush Estate, Penicuik, Midlothian, EH260QB, UK
| | - Michael C Dietze
- Department of Earth & Environment, Boston University, Boston, MA, USA
| | - Florian Hartig
- Theoretical Ecology, University of Regensburg, Universitätsstraße 31, Regensburg, 93053, Germany
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12
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Valente LG, Pitton M, Fürholz M, Oberhaensli S, Bruggmann R, Leib SL, Jakob SM, Resch G, Que YA, Cameron DR. Isolation and characterization of bacteriophages from the human skin microbiome that infect Staphylococcus epidermidis. FEMS Microbes 2021; 2:xtab003. [PMID: 37334235 PMCID: PMC10117716 DOI: 10.1093/femsmc/xtab003] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 03/26/2021] [Indexed: 07/20/2023] Open
Abstract
Phage therapy might be a useful approach for the treatment of nosocomial infections; however, only few lytic phages suitable for this application are available for the opportunistic pathogen, Staphylococcus epidermidis. In the current study, we developed an efficient method to isolate bacteriophages present within the human skin microbiome, by using niche-specific S. epidermidis as the host for phage propagation. Staphylococcus epidermidis was identified on the forehead of 92% of human subjects tested. These isolates were then used to propagate phages present in the same skin sample. Plaques were observable on bacterial lawns in 46% of the cases where S. epidermidis was isolated. A total of eight phage genomes were genetically characterized, including the previously described phage 456. A total of six phage sequences were unique, and spanned each of the major staphylococcal phage families; Siphoviridae (n = 3), Podoviridae (n = 1) and Myoviridae (n = 2). One of the myoviruses (vB_SepM_BE06) was identified on the skin of three different humans. Comparative analysis identified novel genes including a putative N-acetylmuramoyl-L-alanine amidase gene. The host-range of each unique phage was characterized using a panel of diverse staphylococcal strains (n = 78). None of the newly isolated phages infected more than 52% of the S. epidermidis strains tested (n = 44), and non-S. epidermidis strains where rarely infected, highlighting the narrow host-range of the phages. One of the phages (vB_SepM_BE04) was capable of killing staphylococcal cells within biofilms formed on polyurethane catheters. Uncovering a richer diversity of available phages will likely improve our understanding of S. epidermidis-phage interactions, which will be important for future therapy.
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Affiliation(s)
| | | | - Monika Fürholz
- Department of Cardiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Simone Oberhaensli
- Interfaculty Bioinformatics Unit and SIB Swiss Institute of Bioinformatics, University of Bern, Bern, Switzerland
| | - Rémy Bruggmann
- Interfaculty Bioinformatics Unit and SIB Swiss Institute of Bioinformatics, University of Bern, Bern, Switzerland
| | - Stephen L Leib
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Stephan M Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Grégory Resch
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Yok-Ai Que
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - David R Cameron
- Corresponding author: Department of Intensive Care Medicine, Inselspital; Bern University Hospital, 3010 Bern, Switzerland. Tel: +41 31 632 42 55; E-mail:
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13
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Affiliation(s)
- Belén Rodriguez
- Department of Neurosurgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Sandra Nansoz
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - David R Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Werner J Z'Graggen
- Department of Neurosurgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
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14
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Prazak J, Valente L, Iten M, Federer L, Grandgirard D, Soto S, Resch G, Leib SL, Jakob SM, Haenggi M, Cameron DR, Que YA. Benefits of aerosolized phages for the treatment of pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA): an experimental study in rats. J Infect Dis 2021; 225:1452-1459. [PMID: 33668071 PMCID: PMC9016458 DOI: 10.1093/infdis/jiab112] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 02/23/2021] [Indexed: 12/14/2022] Open
Abstract
Background The optimal method for delivering phages in the context of ventilator-associated pneumonia (VAP) is unknown. In the current study, we assessed the utility of aerosolized phages (aerophages) for experimental methicillin-resistant Staphylococcus aureus (MRSA) pneumonia. Methods Rats were ventilated for 4 hours before induction of pneumonia. Animals received one of the following: (1) aerophages; (2) intravenous (IV) phages; (3) a combination of IV and aerophages; (4) IV linezolid; or (5) a combination of IV linezolid and aerophages. Phages were administered at 2, 12, 24, 48, and 72 hours, and linezolid was administered at 2, 12, 24, 36, 48, 60, and 72 hours. The primary outcome was survival at 96 hours. Secondary outcomes were bacterial and phage counts in tissues and histopathological scoring of the lungs. Results Aerophages and IV phages each rescued 50% of animals from severe MRSA pneumonia (P < .01 compared with placebo controls). The combination of aerophages and IV phages rescued 91% of animals, which was higher than either monotherapy (P < .05). Standard-of-care antibiotic linezolid rescued 38% of animals. However, linezolid and aerophages did not synergize in this setting (55% survival). Conclusions Aerosolized phage therapy showed potential for the treatment of MRSA pneumonia in an experimental animal model and warrants further investigation for application in humans.
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Affiliation(s)
- Josef Prazak
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Luca Valente
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.,Institute for Infectious Diseases, University of Bern, Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern Switzerland
| | - Manuela Iten
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Lea Federer
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Denis Grandgirard
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Sara Soto
- Institute of Animal Pathology (COMPATH), Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Gregory Resch
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Stephen L Leib
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Stephan M Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Matthias Haenggi
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - David R Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Yok-Ai Que
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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15
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Bartell JA, Cameron DR, Mojsoska B, Haagensen JAJ, Pressler T, Sommer LM, Lewis K, Molin S, Johansen HK. Bacterial persisters in long-term infection: Emergence and fitness in a complex host environment. PLoS Pathog 2020; 16:e1009112. [PMID: 33315938 PMCID: PMC7769609 DOI: 10.1371/journal.ppat.1009112] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Revised: 12/28/2020] [Accepted: 10/31/2020] [Indexed: 12/20/2022] Open
Abstract
Despite intensive antibiotic treatment, Pseudomonas aeruginosa often persists in the airways of cystic fibrosis (CF) patients for decades, and can do so without antibiotic resistance development. Using high-throughput screening assays of bacterial survival after treatment with high concentrations of ciprofloxacin, we have determined the prevalence of persisters in a large patient cohort using 460 longitudinal isolates of P. aeruginosa from 39 CF patients. Isolates were classed as high persister variants (Hip) if they regrew following antibiotic treatment in at least 75% of the experimental replicates. Strain genomic data, isolate phenotyping, and patient treatment records were integrated in a lineage-based analysis of persister formation and clinical impact. In total, 19% of the isolates were classified as Hip and Hip emergence increased over lineage colonization time within 22 Hip+ patients. Most Hip+ lineages produced multiple Hip isolates, but few Hip+ lineages were dominated by Hip. While we observed no strong signal of adaptive genetic convergence within Hip isolates, they generally emerged in parallel or following the development of ciprofloxacin resistance and slowed growth. Transient lineages were majority Hip-, while strains that persisted over a clinically diagnosed 'eradication' period were majority Hip+. Patients received indistinguishable treatment regimens before Hip emergence, but Hip+ patients overall were treated significantly more than Hip- patients, signaling repeated treatment failure. When subjected to in vivo-similar antibiotic dosing, a Hip isolate survived better than a non-Hip in a structured biofilm environment. In sum, the Hip phenotype appears to substantially contribute to long-term establishment of a lineage in the CF lung environment. Our results argue against the existence of a single dominant molecular mechanism underlying bacterial antibiotic persistence. We instead show that many routes, both phenotypic and genetic, are available for persister formation and consequent increases in strain fitness and treatment failure in CF airways.
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Affiliation(s)
- Jennifer A. Bartell
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - David R. Cameron
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Biljana Mojsoska
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
| | - Janus Anders Juul Haagensen
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs. Lyngby, Denmark
| | | | - Lea M. Sommer
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
| | - Kim Lewis
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Søren Molin
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Helle Krogh Johansen
- Department of Clinical Microbiology, Rigshospitalet, Copenhagen, Denmark
- Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
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16
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Liu S, do Amaral Campos PPZ, Casoni D, Berger D, Kohler A, Bloch A, Bervini D, Setzer F, Cameron DR, Z'Graggen W, Hana A, Langer R, Corrêa TD, Beldi G, Takala J, Jakob SM. Defense mechanisms to increasing back pressure for hepatic oxygen transport and venous return in porcine fecal peritonitis. Am J Physiol Gastrointest Liver Physiol 2020; 319:G289-G302. [PMID: 32658622 DOI: 10.1152/ajpgi.00216.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
High central venous pressure (CVP) acutely decreases venous return. How this affects hepatic oxygen transport in sepsis remains unclear. The aim of this study was to evaluate the effects of repeated increases in CVP via standard nursing procedures (NPs) on hepato-splanchnic and renal oxygen transport in a prolonged porcine sepsis model. Twenty anesthetized and mechanically ventilated pigs with regional hemodynamics monitored were randomized to fecal peritonitis or controls (n = 10 pigs/group). Resuscitation was started after 8 h of observation and continued for 3 days. NPs were performed at baseline and 8 h, 32 h, 56 h, and 72 h after resuscitation started. NPs increased CVP by 4-7 mmHg in both groups. In controls, this was associated with less decrease in hepatic arterial (Qha; 62 ± 70 mL/min) than portal venous flow (Qpv; 364 ± 151 mL/min). Portal venous oxygen content and hepatic O2 delivery (Do2) and consumption (V̇o2) decreased by 11 ± 6 mL/dL and 0.9 ± 0.3 and 0.4 ± 0.3 mL·min-1·kg-1, respectively. In septic animals, hepatic Do2 decreased more in response to increasing CVP (1.5 ± 0.9 mL·min-1·kg-1), which was attributable to a larger fall in both Qha (88 ± 66 ml/min) and portal O2 content (14 ± 10 mL/dL, all P < 0.05). This resulted in numerically lower hepatic V̇o2 since O2 extraction did not increase significantly. In control conditions, a smaller decrease in Qha compared with Qpv helped to limit the reduction in hepatic V̇o2 in response to acute CVP increase. In sepsis, the contribution of Qha to maintain hepatic Do2 was reduced, which jeopardized hepatic V̇o2 further. Renal arterial flow was similarly affected by CVP increase as Qha.NEW & NOTEWORTHY Sepsis impairs intrinsic mechanisms to attenuate effects of increasing back pressure on hepatic oxygen transport.
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Affiliation(s)
- Shengchen Liu
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | | | - Daniela Casoni
- Experimental Surgery Facility, Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - David Berger
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Andreas Kohler
- Department of Visceral Surgery and Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Andreas Bloch
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - David Bervini
- Department of Neurosurgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Florian Setzer
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - David R Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Werner Z'Graggen
- Department of Neurosurgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Anisa Hana
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Rupert Langer
- Institue of Pathology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Thiago D Corrêa
- Department of Intensive Care Unit, Hospital Israelita Albert Einstein, Sao Paulo, Brazil
| | - Guido Beldi
- Department of Visceral Surgery and Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Jukka Takala
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Stephan M Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Qu Y, Li Y, Cameron DR, Easton CD, Zhu X, Zhu M, Salwiczek M, Muir BW, Thissen H, Daley A, Forsythe JS, Peleg AY, Lithgow T. Hyperosmotic Infusion and Oxidized Surfaces Are Essential for Biofilm Formation of Staphylococcus capitis From the Neonatal Intensive Care Unit. Front Microbiol 2020; 11:920. [PMID: 32477314 PMCID: PMC7237634 DOI: 10.3389/fmicb.2020.00920] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 04/17/2020] [Indexed: 11/20/2022] Open
Abstract
Staphylococcus capitis is an opportunistic pathogen often implicated in bloodstream infections in the neonatal intensive care unit (NICU). This is assisted by its ability to form biofilms on indwelling central venous catheters (CVC), which are highly resistant to antibiotics and the immune system. We sought to understand the fundamentals of biofilm formation by S. capitis in the NICU, using seventeen clinical isolates including the endemic NRCS-A clone and assessing nine commercial and two modified polystyrene surfaces. S. capitis clinical isolates from the NICU initiated biofilm formation only in response to hyperosmotic conditions, followed by a developmental progression driven by icaADBC expression to establish mature biofilms, with polysaccharide being their major extracellular polymer substance (EPS) matrix component. Physicochemical features of the biomaterial surface, and in particular the level of the element oxygen present on the surface, significantly influenced biofilm development of S. capitis. A lack of highly oxidized carbon species on the surface prevented the immobilization of S. capitis EPS and the formation of mature biofilms. This information provides guidance in regard to the preparation of hyperosmolar total parenteral nutrition and the engineering of CVC surfaces that can minimize the risk of catheter-related bloodstream infections caused by S. capitis in the NICU.
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Affiliation(s)
- Yue Qu
- The Neonatal Intensive Care Unit, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,Infection and Immunity Theme, Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia.,Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Yali Li
- The Commonwealth Scientific and Industrial Research Organisation (CSIRO) Manufacturing, Clayton, VIC, Australia.,Department of Materials Science and Engineering, Monash Institute of Medical Engineering, Monash University, Clayton, VIC, Australia
| | - David R Cameron
- Infection and Immunity Theme, Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Christopher D Easton
- The Commonwealth Scientific and Industrial Research Organisation (CSIRO) Manufacturing, Clayton, VIC, Australia
| | - Xuebo Zhu
- The Neonatal Intensive Care Unit, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China
| | - Minli Zhu
- The Neonatal Intensive Care Unit, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China
| | - Mario Salwiczek
- Infection and Immunity Theme, Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia.,The Commonwealth Scientific and Industrial Research Organisation (CSIRO) Manufacturing, Clayton, VIC, Australia
| | - Benjamin W Muir
- The Commonwealth Scientific and Industrial Research Organisation (CSIRO) Manufacturing, Clayton, VIC, Australia
| | - Helmut Thissen
- The Commonwealth Scientific and Industrial Research Organisation (CSIRO) Manufacturing, Clayton, VIC, Australia
| | - Andrew Daley
- Department of Microbiology, The Royal Children's Hospital, Parkville, VIC, Australia.,Department of Paediatrics, University of Melbourne, Parkville, VIC, Australia
| | - John S Forsythe
- Department of Materials Science and Engineering, Monash Institute of Medical Engineering, Monash University, Clayton, VIC, Australia
| | - Anton Y Peleg
- Infection and Immunity Theme, Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia.,Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Trevor Lithgow
- Infection and Immunity Theme, Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
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18
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Prazak J, Iten M, Cameron DR, Save J, Grandgirard D, Resch G, Goepfert C, Leib SL, Takala J, Jakob SM, Que YA, Haenggi M. Bacteriophages Improve Outcomes in Experimental Staphylococcus aureus Ventilator-associated Pneumonia. Am J Respir Crit Care Med 2020; 200:1126-1133. [PMID: 31260638 DOI: 10.1164/rccm.201812-2372oc] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Rationale: Infections caused by multidrug-resistant bacteria are a major clinical challenge. Phage therapy is a promising alternative antibacterial strategy.Objectives: To evaluate the efficacy of intravenous phage therapy for the treatment of ventilator-associated pneumonia due to methicillin-resistant Staphylococcus aureus in rats.Methods: In a randomized, blinded, controlled experimental study, we compared intravenous teicoplanin (3 mg/kg, n = 12), a cocktail of four phages (2-3 × 109 plaque-forming units/ml of 2003, 2002, 3A, and K; n = 12), and a combination of both (n = 11) given 2, 12, and 24 hours after induction of pneumonia, and then once daily for 4 days. The primary outcome was survival at Day 4. Secondary outcomes were bacterial and phage densities in lungs and spleen, histopathological scoring of infection within the lungs, and inflammatory biomarkers in blood.Measurements and Main Results: Treatment with either phages or teicoplanin increased survival from 0% to 58% and 50%, respectively (P < 0.005). The combination of phages and antibiotics did not further improve outcomes (45% survival). Animal survival correlated with reduced bacterial burdens in the lung (1.2 × 106 cfu/g of tissue for survivors vs. 1.2 × 109 cfu/g for nonsurviving animals; P < 0.0001), as well as improved histopathological outcomes. Phage multiplication within the lung occurred during treatment. IL-1β increased in all treatment groups over the course of therapy.Conclusions: Phage therapy was as effective as teicoplanin in improving survival and decreasing bacterial load within the lungs of rats infected with methicillin-resistant S. aureus. Combining antibiotics with phage therapy did not further improve outcomes.
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Affiliation(s)
- Josef Prazak
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Manuela Iten
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - David R Cameron
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Jonathan Save
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland; and
| | | | - Gregory Resch
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland; and
| | - Christine Goepfert
- Institute of Animal Pathology, Faculty of Veterinary Medicine, University of Bern, Bern, Switzerland
| | | | - Jukka Takala
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Stephan M Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Yok-Ai Que
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Matthias Haenggi
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Cameron DR, Lin YH, Trouillet-Assant S, Tafani V, Kostoulias X, Mouhtouris E, Skinner N, Visvanathan K, Baines SL, Howden B, Monk IR, Laurent F, Stinear TP, Howden BP, Peleg AY. Vancomycin-intermediate Staphylococcus aureus isolates are attenuated for virulence when compared with susceptible progenitors. Clin Microbiol Infect 2017; 23:767-773. [PMID: 28396035 DOI: 10.1016/j.cmi.2017.03.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 03/29/2017] [Accepted: 03/30/2017] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Vancomycin-intermediate Staphylococcus aureus (VISA) is associated with genetic changes that may also impact upon pathogenicity. In the current study, we compared the virulence of clinical VISA strains with their isogenic vancomycin-susceptible progenitors (VSSA). METHODS Production of the critical virulence protein, α toxin, was assessed using Western blot analysis and was correlated to agr activity using a bioluminescent agr-reporter. Cytotoxicity and intracellular persistence were compared ex vivo for VSSA and VISA within non-professional phagocytes (NPP). Virulence and host immune responses were further explored in vivo using a murine model of bacteraemia. RESULTS VISA isolates produced up to 20-fold less α toxin compared with VSSA, and this was corroborated by either loss of agr activity due to agr mutation, or altered agr activity in the absence of mutation. VISA were less cytotoxic towards NPP and were associated with enhanced intracellular persistence, suggesting that NPP may act as a reservoir for VISA. Infection with VSSA strains produced higher mortality in a murine bacteraemia model (≥90% 7-day mortality) compared with infection with VISA isolates (20% to 50%, p <0.001). Mice infected with VISA produced a dampened immune response (4.6-fold reduction in interleukin-6, p <0.001) and persistent organ bacterial growth was observed for VISA strains out to 7 days. CONCLUSIONS These findings highlight the remarkable adaptability of S. aureus, whereby, in addition to having reduced antibiotic susceptibility, VISA alter the expression of pathogenic factors to circumvent the host immune response to favour persistent infection over acute virulence.
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Affiliation(s)
- D R Cameron
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Australia
| | - Y-H Lin
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute of Infection & Immunity, Australia
| | - S Trouillet-Assant
- Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, International Centre of Infectiology Research, France
| | - V Tafani
- Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, International Centre of Infectiology Research, France
| | - X Kostoulias
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Australia
| | - E Mouhtouris
- Department of Surgery, The University of Melbourne, Australia
| | - N Skinner
- Department of Medicine, The University of Melbourne, Australia
| | - K Visvanathan
- Department of Medicine, The University of Melbourne, Australia
| | - S L Baines
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute of Infection & Immunity, Australia
| | - B Howden
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute of Infection & Immunity, Australia
| | - I R Monk
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute of Infection & Immunity, Australia
| | - F Laurent
- Department of Microbiology, French National Reference Centre for Staphylococci, Hospices Civils de Lyon, International Centre of Infectiology Research, France
| | - T P Stinear
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute of Infection & Immunity, Australia
| | - B P Howden
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute of Infection & Immunity, Australia; Infectious Diseases and Microbiology Departments, Austin Health, Australia.
| | - A Y Peleg
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Australia; Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Australia.
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20
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Cameron DR, Jiang JH, Kostoulias X, Foxwell DJ, Peleg AY. Vancomycin susceptibility in methicillin-resistant Staphylococcus aureus is mediated by YycHI activation of the WalRK essential two-component regulatory system. Sci Rep 2016; 6:30823. [PMID: 27600558 PMCID: PMC5013275 DOI: 10.1038/srep30823] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 06/09/2016] [Indexed: 02/01/2023] Open
Abstract
The treatment of infections caused by methicillin-resistant Staphylococcus aureus is complicated by the emergence of strains with intermediate-level resistance to vancomycin (termed VISA). We have characterised a molecular pathway involved in the in vivo evolution of VISA mediated by the regulatory proteins YycH and YycI. In contrast to their function in other bacterial species, we report a positive role for these auxiliary proteins in regulation of the two-component regulator WalRK. Transcriptional profiling of yycH and yycI deletion mutants revealed downregulation of the ‘WalRK regulon’ including cell wall hydrolase genes atlA and sle1, with functional autolysis assays supporting these data by showing an impaired autolytic phenotype for each deletion strain. Using bacterial-two hybrid assays, we showed that YycH and YycI interact, and that YycHI also interacts with the sensor kinase WalK, forming a ternary protein complex. Mutation to YycH or YycI associated with clinical VISA strains had a deleterious impact on the YycHI/WalK complex, suggesting that the interaction is important for the regulation of WalRK. Taken together, we have described a novel antibiotic resistance strategy for the human pathogen S. aureus, whereby YycHI mutations are selected for in vivo leading to reduced WalRK activation, impaired cell wall turnover and ultimately reduced vancomycin efficacy.
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Affiliation(s)
- David R Cameron
- Department of Microbiology, Monash University, Melbourne, Australia
| | - Jhih-Hang Jiang
- Department of Microbiology, Monash University, Melbourne, Australia
| | - Xenia Kostoulias
- Department of Microbiology, Monash University, Melbourne, Australia
| | - Daniel J Foxwell
- Department of Microbiology, Monash University, Melbourne, Australia
| | - Anton Y Peleg
- Department of Microbiology, Monash University, Melbourne, Australia.,Department of Infectious Diseases, Alfred Hospital and Monash University, Melbourne, Australia
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21
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Cameron DR, Mortin LI, Rubio A, Mylonakis E, Moellering RC, Eliopoulos GM, Peleg AY. Impact of daptomycin resistance on Staphylococcus aureus virulence. Virulence 2016; 6:127-31. [PMID: 25830650 DOI: 10.1080/21505594.2015.1011532] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Daptomycin resistance (DAP(R)) in Staphylococcus aureus is associated with mutations in genes that are also implicated in staphylococcal pathogenesis. Using a laboratory-derived series of DAP exposed strains, we showed a relationship between increasing DAP MIC and reduced virulence in a Galleria mellonella infection model. Point mutations in walK and rpoC led to cumulative reductions in virulence and simultaneous increases in DAP MIC. A point mutation to mprF did not impact on S.aureus virulence; however deletion of mprF led to virulence attenuation and hyper-susceptibility to DAP. To validate our findings in G. mellonella, we confirmed the attenuated virulence of select isolates from the laboratory-derived series using a murine septicaemia model. As a corollary, we showed significant virulence reductions for clinically-derived DAP(R) isolates compared to their isogenic, DAP-susceptible progenitors (DAP(S)). Intriguingly, each clinical DAP(R) isolate was persistent in vivo. Taken together, it appears the genetic correlates underlying daptomycin resistance in S. aureus also alter pathogenicity.
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Affiliation(s)
- David R Cameron
- a Department of Microbiology ; School of Biomedical Sciences; Monash University ; Melbourne , Australia
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22
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Cameron DR, Jiang JH, Hassan KA, Elbourne LDH, Tuck KL, Paulsen IT, Peleg AY. Insights on virulence from the complete genome of Staphylococcus capitis. Front Microbiol 2015; 6:980. [PMID: 26441910 PMCID: PMC4585213 DOI: 10.3389/fmicb.2015.00980] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 09/03/2015] [Indexed: 12/28/2022] Open
Abstract
Staphylococcus capitis is an opportunistic pathogen of the coagulase negative staphylococci (CoNS). Functional genomic studies of S. capitis have thus far been limited by a lack of available complete genome sequences. Here, we determined the closed S. capitis genome and methylome using Single Molecule Real Time (SMRT) sequencing. The strain, AYP1020, harbors a single circular chromosome of 2.44 Mb encoding 2304 predicted proteins, which is the smallest of all complete staphylococcal genomes sequenced to date. AYP1020 harbors two large mobile genetic elements; a plasmid designated pAYP1020 (59.6 Kb) and a prophage, ΦAYP1020 (48.5 Kb). Methylome analysis identified significant adenine methylation across the genome involving two distinct methylation motifs (1972 putative 6-methyladenine (m6A) residues identified). Putative adenine methyltransferases were also identified. Comparative analysis of AYP1020 and the closely related CoNS, S. epidermidis RP62a, revealed a host of virulence factors that likely contribute to S. capitis pathogenicity, most notably genes important for biofilm formation and a suite of phenol soluble modulins (PSMs); the expression/production of these factors were corroborated by functional assays. The complete S. capitis genome will aid future studies on the evolution and pathogenesis of the coagulase negative staphylococci.
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Affiliation(s)
- David R Cameron
- Department of Microbiology, Monash University Melbourne, VIC, Australia
| | - Jhih-Hang Jiang
- Department of Microbiology, Monash University Melbourne, VIC, Australia
| | - Karl A Hassan
- Department of Chemistry and Biomolecular Sciences, Macquarie University Sydney, NSW, Australia
| | - Liam D H Elbourne
- Department of Chemistry and Biomolecular Sciences, Macquarie University Sydney, NSW, Australia
| | - Kellie L Tuck
- School of Chemistry, Monash University Melbourne, VIC, Australia
| | - Ian T Paulsen
- Department of Chemistry and Biomolecular Sciences, Macquarie University Sydney, NSW, Australia
| | - Anton Y Peleg
- Department of Microbiology, Monash University Melbourne, VIC, Australia ; Department of Infectious Diseases, Alfred Hospital Melbourne, VIC, Australia
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Gao W, Cameron DR, Davies JK, Kostoulias X, Stepnell J, Tuck KL, Yeaman MR, Peleg AY, Stinear TP, Howden BP. The RpoB H₄₈₁Y rifampicin resistance mutation and an active stringent response reduce virulence and increase resistance to innate immune responses in Staphylococcus aureus. J Infect Dis 2012; 207:929-39. [PMID: 23255563 DOI: 10.1093/infdis/jis772] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The occurrence of mutations in methicillin-resistant Staphylococcus aureus (MRSA) during persistent infection leads to antimicrobial resistance but may also impact host-pathogen interactions. Here, we investigate the host-pathogen consequences of 2 mutations arising in clinical MRSA during persistent infection: RpoB H₄₈₁Y, which is linked to rifampicin resistance, and RelA F₁₂₈Y, which is associated with an active stringent response. Allelic exchange experiments showed that both mutations cause global transcriptional changes, leading to upregulation of capsule production, with attenuated virulence in a murine bacteremia model and reduced susceptibility to both antimicrobial peptides and whole-blood killing. Disruption of capsule biosynthesis reversed these impacts on innate immune function. These data clearly link MRSA persistence and reduced virulence to the same mechanisms that alter antimicrobial susceptibility. Our study highlights the wider consequences of suboptimal antimicrobial use, where drug resistance and immune escape mechanisms coevolve, thus increasing the likelihood of treatment failure.
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Affiliation(s)
- Wei Gao
- Infectious Diseases Department, Austin Centre for Infection Research, University of Melbourne, Australia
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24
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Cameron DR, Ward DV, Kostoulias X, Howden BP, Moellering RC, Eliopoulos GM, Peleg AY. Serine/threonine phosphatase Stp1 contributes to reduced susceptibility to vancomycin and virulence in Staphylococcus aureus. J Infect Dis 2012; 205:1677-87. [PMID: 22492855 DOI: 10.1093/infdis/jis252] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The genetic mechanisms that contribute to reduced susceptibility to vancomycin in Staphylococcus aureus are complex and heterogeneous. In addition, debate is emerging as to the true effect of reduced susceptibility to vancomycin on staphylococcal virulence. To investigate this, comparative genomics was performed on a collection of vancomycin-exposed isogenic S. aureus pairs (14 strains in total). Previously described mutations were observed in genes such as vraG, agrA, yvqF, and rpoB; however, a new mechanism was identified involving a serine/threonine phosphatase, Stp1. After constructing an stp1 deletion mutant, we showed that stp1 is important in vancomycin susceptibility and cell wall biosynthesis. Gene expression studies showed that stp1 also regulates virulence genes, including a hemolysin, superantigen-like protein, and phenol-soluble modulin, and that the deletion mutant is attenuated in virulence in vivo. Stp1 provides a new link between vancomycin susceptibility and virulence in S. aureus.
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Affiliation(s)
- David R Cameron
- Department of Microbiology, Monash University, Melbourne, Australia
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25
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Cameron DR, Howden BP, Peleg AY. The interface between antibiotic resistance and virulence in Staphylococcus aureus and its impact upon clinical outcomes. Clin Infect Dis 2012; 53:576-82. [PMID: 21865195 DOI: 10.1093/cid/cir473] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The ability of Staphylococcus aureus to rapidly acquire antibiotic resistance in the face of antimicrobial challenge has enabled it to remain an ongoing, significant human pathogen. Mechanisms behind the evolution of resistance in S. aureus are well documented, but the effects of these phenotypes upon virulence are less clear. By exploring available clinical and experimental data, we have shown that a number of the major steps in the evolution of antibacterial resistance in S. aureus have been accompanied by alterations in virulence. This review also highlights that further experimentation is required to fully elucidate the mechanisms involved in the interface between virulence and antibiotic resistance, with the intention of identifying novel preventative or therapeutic strategies for this important human pathogen.
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Affiliation(s)
- David R Cameron
- Department of Microbiology, Monash University, Melbourne, Australia
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26
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Peleg AY, Miyakis S, Ward DV, Earl AM, Rubio A, Cameron DR, Pillai S, Moellering RC, Eliopoulos GM. Whole genome characterization of the mechanisms of daptomycin resistance in clinical and laboratory derived isolates of Staphylococcus aureus. PLoS One 2012; 7:e28316. [PMID: 22238576 PMCID: PMC3253072 DOI: 10.1371/journal.pone.0028316] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 11/06/2011] [Indexed: 11/24/2022] Open
Abstract
Background Daptomycin remains one of our last-line anti-staphylococcal agents. This study aims to characterize the genetic evolution to daptomycin resistance in S. aureus. Methods Whole genome sequencing was performed on a unique collection of isogenic, clinical (21 strains) and laboratory (12 strains) derived strains that had been exposed to daptomycin and developed daptomycin-nonsusceptibility. Electron microscopy (EM) and lipid membrane studies were performed on selected isolates. Results On average, six coding region mutations were observed across the genome in the clinical daptomycin exposed strains, whereas only two mutations on average were seen in the laboratory exposed pairs. All daptomycin-nonsusceptible strains had a mutation in a phospholipid biosynthesis gene. This included mutations in the previously described mprF gene, but also in other phospholipid biosynthesis genes, including cardiolipin synthase (cls2) and CDP-diacylglycerol-glycerol-3-phosphate 3-phosphatidyltransferase (pgsA). EM and lipid membrane composition analyses on two clinical pairs showed that the daptomycin-nonsusceptible strains had a thicker cell wall and an increase in membrane lysyl-phosphatidylglycerol. Conclusion Point mutations in genes coding for membrane phospholipids are associated with the development of reduced susceptibility to daptomycin in S. aureus. Mutations in cls2 and pgsA appear to be new genetic mechanisms affecting daptomycin susceptibility in S. aureus.
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Affiliation(s)
- Anton Y Peleg
- Department of Microbiology, School of Biomedical Sciences, Monash University, Melbourne, Australia.
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27
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Grayson ML, Mahony AA, Grabsch EA, Cameron DR, Martin RD, Heland M, Petty M, Xie S. Marked reductions in rates of vancomycin-resistant enterococci (VRE) colonization & disease associated with introduction of a routine hospital-wide bleach cleaning program. BMC Proc 2011. [PMCID: PMC3239666 DOI: 10.1186/1753-6561-5-s6-p24] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Affiliation(s)
- D R Cameron
- University of California, Berkeley, California
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Abstract
Despite increasing attention to the human dimension of conservation projects, a rigorous, systematic methodology for planning for ecosystem services has not been developed. This is in part because flows of ecosystem services remain poorly characterized at local-to-regional scales, and their protection has not generally been made a priority. We used a spatially explicit conservation planning framework to explore the trade-offs and opportunities for aligning conservation goals for biodiversity with six ecosystem services (carbon storage, flood control, forage production, outdoor recreation, crop pollination, and water provision) in the Central Coast ecoregion of California, United States. We found weak positive and some weak negative associations between the priority areas for biodiversity conservation and the flows of the six ecosystem services across the ecoregion. Excluding the two agriculture-focused services-crop pollination and forage production-eliminates all negative correlations. We compared the degree to which four contrasting conservation network designs protect biodiversity and the flow of the six services. We found that biodiversity conservation protects substantial collateral flows of services. Targeting ecosystem services directly can meet the multiple ecosystem services and biodiversity goals more efficiently but cannot substitute for targeted biodiversity protection (biodiversity losses of 44% relative to targeting biodiversity alone). Strategically targeting only biodiversity plus the four positively associated services offers much promise (relative biodiversity losses of 7%). Here we present an initial analytical framework for integrating biodiversity and ecosystem services in conservation planning and illustrate its application. We found that although there are important potential trade-offs between conservation for biodiversity and for ecosystem services, a systematic planning framework offers scope for identifying valuable synergies.
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Affiliation(s)
- Kai M A Chan
- Center for Conservation Biology, Department of Biological Sciences, Stanford University, Stanford, California, USA.
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Hoy PM, Cameron DR, Helle SS, Duff SJ. Production of a recombinant protein using Pichia pastoris grown in evaporator condensate from a Kraft pulp mill. Enzyme Microb Technol 2006. [DOI: 10.1016/j.enzmictec.2004.07.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Helle SS, Murray A, Lam J, Cameron DR, Duff SJB. Xylose fermentation by genetically modified Saccharomyces cerevisiae 259ST in spent sulfite liquor. Bioresour Technol 2004; 92:163-171. [PMID: 14693449 DOI: 10.1016/j.biortech.2003.08.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Spent sulfite pulping liquor (SSL) is a high-organic content byproduct of acid bisulfite pulp manufacture which is fermented to make industrial ethanol. SSL is typically concentrated to 240 g/l (22% w/w) total solids prior to fermentation, and contains up to 24 g/l xylose and 30 g/l hexose sugars, depending upon the wood species used. The xylose present in SSL is difficult to ferment using natural xylose-fermenting yeast strains due to the presence of inhibitory compounds, such as organic acids. Using sequential batch shake flask experiments, Saccharomyces cerevisiae 259ST, which had been genetically modified to ferment xylose, was compared with the parent strain, 259A, and an SSL adapted strain, T2, for ethanol production during SSL fermentation. With an initial SSL pH of 6, without nutrient addition or SSL pretreatment, the ethanol yield ranged from 0.32 to 0.42 g ethanol/g total sugar for 259ST, compared to 0.15-0.32 g ethanol/g total sugar for non-xylose fermenting strains. For most fermentations, minimal amounts of xylitol (<1 g/l) were produced, and glycerol yields were approximately 0.12 g glycerol/g sugar consumed. By using 259ST for SSL fermentation up to 130% more ethanol can be produced compared to fermentations using non-xylose fermenting yeast.
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Affiliation(s)
- Steve S Helle
- UBC Department of Chemical and Biological Engineering, 2216 Main Mall, Vancouver, BC, Canada V6T 1Z4
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Proudfoot JR, Betageri R, Cardozo M, Gilmore TA, Glynn S, Hickey ER, Jakes S, Kabcenell A, Kirrane TM, Tibolla AK, Lukas S, Patel UR, Sharma R, Yazdanian M, Moss N, Beaulieu PL, Cameron DR, Ferland JM, Gauthier J, Gillard J, Gorys V, Poirier M, Rancourt J, Wernic D, Llinas-Brunet M. Nonpeptidic, monocharged, cell permeable ligands for the p56lck SH2 domain. J Med Chem 2001; 44:2421-31. [PMID: 11448224 DOI: 10.1021/jm000446q] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
p56lck is a member of the src family of tyrosine kinases and plays a critical role in the signal transduction events that lead to T cell activation. Ligands for the p56lck SH2 domain have the potential to disrupt the interaction of p56lck with its substrates and derail the signaling cascade that leads to the production of cytokines such as interleukin-2. Starting from the quintuply charged (at physiological pH) phosphorylated tetrapeptide, AcpYEEI, we recently disclosed (J. Med. Chem. 1999, 42, 722 and J. Med. Chem. 1999, 42, 1757) the design of the modified dipeptide 3, which carries just two charges at physiological pH. Here we present the elaboration of 3 to the nonpeptidic, monocharged compound, 9S. This molecule displays good binding affinity for the p56lck SH2 domain (K(d) 1 microM) and good cell permeation, and this combination of properties allowed us to demonstrate clear-cut inhibitory effects on a very early event in T cell activation, namely calcium mobilization.
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Affiliation(s)
- J R Proudfoot
- Boehringer Ingelheim (Canada) Ltd., Research and Development, 2100 Cunard Street, Laval, Quebec H7S 2G5, Canada.
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Poupart MA, Cameron DR, Chabot C, Ghiro E, Goudreau N, Goulet S, Poirier M, Tsantrizos YS. Solid-phase synthesis of peptidomimetic inhibitors for the hepatitis C virus NS3 protease. J Org Chem 2001; 66:4743-51. [PMID: 11442398 DOI: 10.1021/jo010164d] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The NS3 serine protease enzyme of the hepatitis C virus (HCV) is essential for viral replication. Short peptides mimicking the N-terminal substrate cleavage products of the NS3 protease are known to act as weak inhibitors of the enzyme and have been used as templates for the design of peptidomimetic inhibitors. Automated solid-phase synthesis of a small library of compounds based on such a peptidomimetic scaffold has led to the identification of potent and highly selective inhibitors of the NS3 protease enzyme.
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Affiliation(s)
- M A Poupart
- Department of Chemistry, Boehringer Ingelheim (Canada) Ltd., Quebec H7S 2G5, Canada
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36
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LaPlante SR, Aubry N, Bonneau PR, Kukolj G, Lamarre D, Lefebvre S, Li H, Llinàs-Brunet M, Plouffe C, Cameron DR. NMR line-broadening and transferred NOESY as a medicinal chemistry tool for studying inhibitors of the hepatitis C virus NS3 protease domain. Bioorg Med Chem Lett 2000; 10:2271-4. [PMID: 11055336 DOI: 10.1016/s0960-894x(00)00466-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This work describes the use of NMR as a medicinal chemistry tool for better understanding the binding characteristics of inhibitors of the HCV NS3 protease. The protease-bound structure of a tetrapeptide-like inhibitor that has an acid C-terminus, a norvaline at P1 and a naphthylmethoxy proline at P2 is described. Conformational comparisons are made with a similar compound having a 1-amino-cyclopropylcarboxylic acid at P1 and with a hexapeptide inhibitor. Differences between the free and bound states are identified. 19F NMR also helped in determining that a single complex is observed when an inhibitor is added to the protease at a 1:1 ratio.
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Affiliation(s)
- S R LaPlante
- Department of Chemistry, Boehringer Ingelheim, Laval, Québec, Canada.
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37
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Beaulieu PL, Anderson PC, Cameron DR, Croteau G, Gorys V, Grand-Maître C, Lamarre D, Liard F, Paris W, Plamondon L, Soucy F, Thibeault D, Wernic D, Yoakim C, Pav S, Tong L. 2',6'-Dimethylphenoxyacetyl: a new achiral high affinity P(3)-P(2) ligand for peptidomimetic-based HIV protease inhibitors. J Med Chem 2000; 43:1094-108. [PMID: 10737742 DOI: 10.1021/jm990336n] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Starting from palinavir (1), our lead HIV protease inhibitor, we have discovered a new series of truncated analogues in which the P(3)-P(2) quinaldic-valine portion of 1 was replaced by 2', 6'-dimethylphenoxyacetyl. With EC(50)'s in the 1-2 nM range, some of these compounds are among the most potent inhibitors of HIV replication in vitro, reported to date. One of the most promising members in this series (compound 27, BILA 2185 BS) exhibited a favorable overall pharmacokinetic profile, with 61% apparent oral bioavailability in rat. X-ray crystal structures and molecular modeling were used to rationalize the high potency resulting from incorporation of this structurally simple, achiral ligand into the P(3)-P(2) position of hydroxyethylamine-based HIV protease inhibitors.
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Affiliation(s)
- P L Beaulieu
- Boehringer Ingelheim Pharmaceuticals Inc., 175 Briar Ridge Road, Ridgefield, Connecticut 06877, USA.
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LaPlante SR, Cameron DR, Aubry N, Lefebvre S, Kukolj G, Maurice R, Thibeault D, Lamarre D, Llinàs-Brunet M. Solution structure of substrate-based ligands when bound to hepatitis C virus NS3 protease domain. J Biol Chem 1999; 274:18618-24. [PMID: 10373473 DOI: 10.1074/jbc.274.26.18618] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The interactions of the NS3 protease domain with inhibitors that are based on N-terminal cleavage products of peptide substrates were studied by NMR methods. Transferred nuclear Overhauser effect experiments showed that these inhibitors bind the protease in a well defined, extended conformation. Protease-induced line-broadening studies helped identify the segments of inhibitors which come into contact with the protease. A comparison of the NMR data of the free and protease-bound states suggests that these ligands undergo rigidification upon complexation. This work provides the first structure of an inhibitor when bound to NS3 protease and should be valuable for designing more potent inhibitors.
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Affiliation(s)
- S R LaPlante
- Departments of Chemistry and Biological Sciences, Boehringer Ingelheim (Canada) Ltd., Bio-Méga Research Division, Laval, Québec H7S 2G5, Canada.
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Beaulieu PL, Cameron DR, Ferland JM, Gauthier J, Ghiro E, Gillard J, Gorys V, Poirier M, Rancourt J, Wernic D, Llinas-Brunet M, Betageri R, Cardozo M, Hickey ER, Ingraham R, Jakes S, Kabcenell A, Kirrane T, Lukas S, Patel U, Proudfoot J, Sharma R, Tong L, Moss N. Ligands for the tyrosine kinase p56lck SH2 domain: discovery of potent dipeptide derivatives with monocharged, nonhydrolyzable phosphate replacements. J Med Chem 1999; 42:1757-66. [PMID: 10346928 DOI: 10.1021/jm980676t] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
p56lck is a member of the src family of tyrosine kinases. Through modular binding units called SH2 domains, p56lck promotes phosphotyrosine-dependent protein-protein interactions and plays a critical role in signal transduction events that lead to T-cell activation. Starting from the phosphorylated dipeptide (2), a high-affinity ligand for the p56lck SH2 domain, we have designed novel dipeptides that contain monocharged, nonhydrolyzable phosphate group replacements and bind to the protein with KD's in the low micromolar range. Replacement of the phosphate group in phosphotyrosine-containing sequences by a (R/S)-hydroxyacetic (compound 8) or an oxamic acid (compound 10) moiety leads to hydrolytically stable, monocharged ligands, with 83- and 233-fold decreases in potency, respectively. This loss in binding affinity can be partially compensated for by incorporating large lipophilic groups at the inhibitor N-terminus. These groups provide up to 13-fold increases in potency depending on the nature of the phosphate replacement. The discovery of potent (2-3 microM), hydrolytically stable dipeptide derivatives, bearing only two charges at physiological pH, represents a significant step toward the discovery of compounds with cellular activity and the development of novel therapeutics for conditions associated with undesired T-cell proliferation.
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Affiliation(s)
- P L Beaulieu
- Boehringer Ingelheim Pharmaceuticals Inc., 175 Briar Ridge Road, Ridgefield, Connecticut 06877, USA
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40
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Llinaś-Brunet M, Beaulieu PL, Cameron DR, Ferland JM, Gauthier J, Ghiro E, Gillard J, Gorys V, Poirier M, Rancourt J, Wernic D, Betageri R, Cardozo M, Jakes S, Lukas S, Patel U, Proudfoot J, Moss N. Phosphotyrosine-containing dipeptides as high-affinity ligands for the p56lck SH2 domain. J Med Chem 1999; 42:722-9. [PMID: 10052978 DOI: 10.1021/jm980612i] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Src homology-2 (SH2) domains are noncatalytic motifs containing approximately 100 amino acid residues that are involved in intracellular signal transduction. The phosphotyrosine-containing tetrapeptide Ac-pYEEI binds to the SH2 domain of p56lck (Lck) with an affinity of 0.1 microM. Starting from Ac-pYEEI, we have designed potent antagonists of the Lck SH2 domain which are reduced in peptidic character and in which the three carboxyl groups have been eliminated. The two C-terminal amino acids (EI) have been replaced by benzylamine derivatives and the pY + 1 glutamic acid has been substituted with leucine. The best C-terminal fragment identified, (S)-1-(4-isopropylphenyl)ethylamine, binds to the Lck SH2 domain better than the C-terminal dipeptide EI. Molecular modeling suggests that the substituents at the 4-position of the phenyl ring occupy the pY + 3 lipophilic pocket in the SH2 domain originally occupied by the isoleucine side chain. This new series of phosphotyrosine-containing dipeptides binds to the Lck SH2 domain with potencies comparable to that of tetrapeptide 1.
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Affiliation(s)
- M Llinaś-Brunet
- Boehringer Ingelheim Pharmaceuticals Inc., 175 Briar Ridge Road, Ridgefield, Connecticut 06877, USA
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Yoakim C, Ogilvie WW, Cameron DR, Chabot C, Grand-Maître C, Guse I, Haché B, Kawai S, Naud J, O'Meara JA, Plante R, Déziel R. Potent beta-lactam inhibitors of human cytomegalovirus protease. Antivir Chem Chemother 1998; 9:379-87. [PMID: 9875391 DOI: 10.1177/095632029800900502] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A series of novel monobactam inhibitors of human cytomegalovirus (HCMV) protease has been described that possess a heterocyclic thiomethyl side chain at C-4. Changes to the heterocycle did not significantly change the inhibitory activity of these compounds in an enzymatic assay, although improvements in solubility and cell culture activity were noted. A number of permutations between C-4 substitutions and N-1 derivatives led to the identification of several beta-lactams with antiviral activity in a plaque reduction assay. N-methyl thiotetrazole-containing compounds were found to be the most potent inhibitors in the enzymatic assay.
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Affiliation(s)
- C Yoakim
- Bio-Méga Research Division, Boehringer Ingelheim (Canada), Laval, Québec.
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Abstract
INTRODUCTION The effect of burns surgery that requires intraoperative transfusion of five or more units of blood on serum vancomycin levels was assessed. METHODS Serum vancomycin levels were measured 10 min and 6 h after vancomycin administration with surgery being performed in the interval. The following day the same dose of vancomycin was given and serum vancomycin levels measured at the same times without intervening surgery. RESULTS Thirteen operations involving nine patients who required a mean blood transfusion of 9.2 units were studied. There was very little difference between 10-min levels, 6-h levels and the change over interval (absolute and percentage) on the day of surgery and the following day. The recorded serum levels were often at the lower end of the desired range, especially in patients who underwent the larger operations. This was the case on both day of surgery and the control day. CONCLUSIONS Large volume blood loss and replacement during burns surgery did not significantly affect perioperative vancomycin levels. 1998 Elsevier Science Ltd for ISBI.
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Affiliation(s)
- D R Cameron
- Royal Brisbane Hospital, Herston, Queensland, Australia
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Yoakim C, Ogilvie WW, Cameron DR, Chabot C, Guse I, Haché B, Naud J, O'Meara JA, Plante R, Déziel R. beta-Lactam derivatives as inhibitors of human cytomegalovirus protease. J Med Chem 1998; 41:2882-91. [PMID: 9667976 DOI: 10.1021/jm980131z] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The development of novel monobactam inhibitors of HCMV protease incorporating a carbon side chain at C-4 and a urea function at N-1 is described. Substitution with small groups at the C-3 position of the beta-lactam ring gave an increase in enzymatic activity and in stability; however, a lack of selectivity against other serine proteases was noted. The use of both tri- and tetrasubstituted urea functionalities gave effective inhibitors of HCMV protease. Benzyl substitution of the urea moiety was beneficial, especially when strong electron-withdrawing groups where attached at the para position. Modest antiviral activity was found in a plaque reduction assay.
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Affiliation(s)
- C Yoakim
- Bio-Méga Research Division, Boehringer Ingelheim (Canada) Ltd., 2100 Cunard Street, Laval, Québec H7S 2G5, Canada.
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LaPlante SR, Aubry N, Bonneau PR, Cameron DR, Lagacé L, Massariol MJ, Montpetit H, Plouffe C, Kawai SH, Fulton BD, Chen Z, Ni F. Human cytomegalovirus protease complexes its substrate recognition sequences in an extended peptide conformation. Biochemistry 1998; 37:9793-801. [PMID: 9657693 DOI: 10.1021/bi980555v] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Substrate hydrolysis by human cytomegalovirus (HCMV) protease is essential to viral capsid assembly. The interaction of HCMV protease and the N-terminal cleavage products of the hydrolysis of R- and M-site oligopeptide substrate mimics (R and M, respectively, which span the P9-P1 positions) was studied by NMR methods. Protease-induced differential line broadening indicated that ligand binding is mediated by the P4-P1 amino acid residues of the peptides. A well-defined extended conformation of R from P1 through P4 when complexed to HCMV protease was evidenced by numerous transferred nuclear Overhauser effect (NOE) correlations for the peptide upon addition of the enzyme. NOE cross-peaks between the P4 and P5 side chains placing these two groups in proximity indicated a deviation from the extended conformation starting at P5. Similar studies carried out for the M peptide also indicated an extended peptide structure very similar to that of R, although the conformation of the P5 glycine could not be established. No obvious variation in structure between bound R and M (notably at P4, where the tyrosine of the R-site has been suggested to play a key role in ligand binding) could be discerned that might explain the observed differences in processing rates between R- and M-sequences. Kinetic studies, utilizing R- and M-site peptide substrates for which the P5 and P4 residues were separately exchanged, revealed that these positions had essentially no influence on the specificity constants (kcat/KM). In sharp contrast, substitution of the P2 residue of an M-site peptide changed its specificity constant to that of an R-site peptide substrate, and vice versa.
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Affiliation(s)
- S R LaPlante
- Biomolecular NMR Laboratory, Biotechnology Research Institute, National Research Council of Canada, Montréal, Québec
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Abstract
Self-inflicted burns are a regular source of admissions to burns units world wide. This study examines the characteristics and outcomes of those who deliberately burn themselves. The medical records of all patients admitted to the Royal Brisbane Hospital Burns Unit and identified as having suffered a self-inflicted burn between 1990 and 1995 were reviewed. The records of patients who doused themselves with flammable liquid between 1984 and 1995 were examined as a separate group. Of 1072 admissions there were 44 cases (4.1 per cent) of deliberately self-inflicted burns. Average age was 30 yr with an average total burn surface area (TBSA) of 30 per cent (range 1-98 per cent). Schizophrenia, depression and personality disorder were diagnosed in 71 per cent. Alcohol intoxication was common in the rest. Suicide attempters were almost all male and the majority (60 per cent) were diagnosed with a major psychiatric illness. Self-mutilators suffered much less serious burns and none died. Self-inflicted burns accounted for 24 per cent of burns admitted to the intensive care unit. Self-immolation with flammable liquid resulted in severe burns with a 45 per cent mortality. A number of differences was demonstrated between those patients who had attempted suicide and those who had deliberately burnt themselves without suicidal attempt. Self-immolators constitute a considerable proportion of major burns admitted to this unit.
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Affiliation(s)
- D R Cameron
- Burns Unit, Royal Brisbane Hospital, Herston, Queensland, Australia
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46
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Smith MT, Cameron DR, Duff SJ. Comparison of industrial yeast strains for fermentation of spent sulphite pulping liquor fortified with wood hydrolysate. J Ind Microbiol Biotechnol 1997; 18:18-21. [PMID: 9079283 DOI: 10.1038/sj.jim.2900338] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ethanol production from spent sulphite pulping liquor (SSL) was compared for four different yeasts. A second strain of S. cerevisiae as well as a 2-deoxyglucose-resistant strain formed through protoplast fusions between S. uvarum and S. diastaticus produced up to 27% more ethanol from SSL fortified with hydrolysis sugars than was produced by S. cerevisiae. The incremental improvement in ethanol yield appeared to vary with the degree of fortification, ranging from 5.8% for unfortified SSL, to 27% for the highest level of fortification tested. Decreasing fermentation rates were observed for SSL fortified with glucose, mannose and galactose, respectively. Sugar uptake rates in SSL fortified with glucose, galactose and mannose were 6.8, 2.8 and 2.0 g L-1 h-1, respectively. However, when these sugars were fermented along with a glucose cosubstrate, the rate at which the combined glucose/mannose medium was fermented was nearly identical to that of the glucose control.
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Affiliation(s)
- M T Smith
- UBC Pulp and Paper Centre, University of British Columbia, Vancouver, Canada
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Abstract
The mannoprotein which is a major component of the cell wall of Saccharomyces cerevisiae is an effective bioemulsifier. Mannoprotein emulsifier was extracted in a high yield from whole cells of fresh bakers' yeast by two methods, by autoclaving in neutral citrate buffer and by digestion with Zymolase (Miles Laboratories; Toronto, Ontario, Canada), a beta-1,3-glucanase. Heat-extracted emulsifier was purified by ultrafiltration and contained approximately 44% carbohydrate (mannose) and 17% protein. Treatment of the emulsifier with protease eliminated emulsification. Kerosene-in-water emulsions were stabilized over a broad range of conditions, from pH 2 to 11, with up to 5% sodium chloride or up to 50% ethanol in the aqueous phase. In the presence of a low concentration of various solutes, emulsions were stable to three cycles of freezing and thawing. An emulsifying agent was extracted from each species or strain of yeast tested, including 13 species of genera other than Saccharomyces. Spent yeast from the manufacture of beer and wine was demonstrated to be a possible source for the large-scale production of this bioemulsifier.
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Affiliation(s)
- D R Cameron
- Department of Chemical Engineering, McGill University, Montreal, Quebec, Canada
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Coulton JW, Mason P, Cameron DR, Carmel G, Jean R, Rode HN. Protein fusions of beta-galactosidase to the ferrichrome-iron receptor of Escherichia coli K-12. J Bacteriol 1986; 165:181-92. [PMID: 3079747 PMCID: PMC214387 DOI: 10.1128/jb.165.1.181-192.1986] [Citation(s) in RCA: 108] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The fusion-generating phage lambda plac Mu1 was used to produce fusions of lacZ to fhuA, the gene encoding the ferrichrome-iron receptor (FhuA protein) in the outer membrane of Escherichia coli K-12. Fusions to the fhuA gene in a delta (lac) strain were selected by their resistance to bacteriophage phi 80 vir. Ten independent (fhuA'-'lacZ) fusions were all Lac+ and were resistant to the lethal agents which require the FhuA protein as receptor, i.e., phi 80 vir, T5, T1, UC-1, and colicin M; none could utilize ferrichrome as the sole iron source. Specialized transducing phages were obtained by illegitimate excision from the chromosome of each of the fusion-bearing strains, and EcoRI fragments which encoded the fusions were subcloned into the high-copy plasmid pMLB524. Physical mapping of the fusion-containing plasmids confirmed the presence of three restriction sites which were also located on the chromosomal DNA of sequences near the fhuA gene. The direction of transcription of the fhuA gene was deduced from the direction of transcription of the (fhuA'-'lacZ) gene fusion. Identification of the chimeric proteins was made by both radiolabeling cells and immunoprecipitating the LacZ-containing proteins with antibody to beta-galactosidase and by preparing whole cell extracts from Lac+ cells containing the cloned gene fusions. Two sizes of (FhuA'-'LacZ) proteins were detected, 121 kDa and 124 kDa. The DNA sequences at the unique fusion joints were determined. The sequence information allowed us to identify three distinct fusion joints which were grouped as follows, type I fusions, 5'-ACT GCT CAG CCA A-3'; type IIa fusions, 5'-GCG GTT GAA CCG A-3'; and type IIb fusions: 5'-ACC GCT GCA CCT G-3'. To orient these fhuA fusion joints, the complete nucleotide sequence of the fhuA gene was determined from a 2,902-base-pair fragment of DNA. A single open reading frame was found which translated into a 747-amino acid polypeptide. The signal sequence of 33 amino acids was followed by a mature protein with a molecular weight of 78,992. Alignment of the amino acid sequence of the FhuA protein with the amino acid sequences presented for two other tonB-dependent receptor proteins in the outer membrane of E. coli showed an area of local homology at the amino terminus of all three proteins.
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Vernet T, McDonald IJ, Cameron DR, Visentin LP. Stable maintenance in chemostat-grown Escherichia coli of pBR322 and pACYC184 by disruption of the tetracycline resistance gene. Biosci Rep 1985; 5:29-37. [PMID: 3886036 DOI: 10.1007/bf01117438] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Plasmid stability was studied in antibiotic-free chemostat cultures. Disruption, either by deletion or insertion, of the tetracycline resistance gene in the EcoR1/EcoRV region of the cloning vector pBR322 or in the HindIII/BamH1 region of pACYC184 yields plasmids markedly more stable than the parent plasmids. Thus, at least for these two instances, cloning of a partitioning (par) locus is not prerequisite for plasmid maintenance.
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Cameron DR, Moav RM. INHERITANCE IN NICOTIANA TABACUM XXVII. POLLEN KILLER, AN ALIEN GENETIC LOCUS INDUCING ABORTION OF MICROSPORES NOT CARRYING IT. Genetics 1957; 42:326-35. [PMID: 17247701 PMCID: PMC1209835 DOI: 10.1093/genetics/42.3.326] [Citation(s) in RCA: 62] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- D R Cameron
- Department of Genetics, University of California
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