The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Andrej Trampuz - One of the best experts on this subject based on the ideXlab platform.
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Susceptibility testing of Mycobacterium abscessus by isothermal Microcalorimetry
Diagnostic microbiology and infectious disease, 2015Co-Authors: Noémie Boillat-blanco, Ulrika Furustrand Tafin, Katia Jaton, Andrej TrampuzAbstract:Abstract We evaluated a new method for susceptibility testing of a rapidly growing mycobacterium using real-time measurement of heat (Microcalorimetry). MICs of 2 clinical Mycobacterium abscessus isolates were determined by microbroth dilution and E-test. For Microcalorimetry, Middlebrook-7H10 agar+10% oleic acid–albumin–dextrose–catalase, containing amikacin, clarithromycin, linezolid, and ciprofloxacin was inoculated with ~10 5 CFU/mL. Heat production was measured at 37°C for 72h. Minimal heat inhibition concentration (MHIC) was defined as the lowest antibiotic concentration inhibiting growth-related heat production. Growth of M. abscessus was detected after a median of 16.5h (range, 8.5–26.9h). Heat detection was proportionally delayed with increasing concentration of antibiotics. MHICs for the tested strains were 16 to >16mg/L for amikacin, >8mg/L for clarithromycin, 4 to >16mg/L for ciprofloxacin, 24 to >32mg/L for linezolid. MHICs were in agreement within two 2-fold dilutions with conventional MICs. Microcalorimetry may accelerate antimicrobial susceptibility testing in mycobacteria and provide additional real-time information on the drug effect.
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The potential use of Microcalorimetry in rapid differentiation between septic arthritis and other causes of arthritis
European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology, 2014Co-Authors: Erlangga Yusuf, Thomas Hügle, Thomas Daikeler, C. Voide, Olivier Borens, Andrej TrampuzAbstract:Current diagnostic methods in differentiating septic from non-septic arthritis are time-consuming (culture) or have limited sensitivity (Gram stain). Microcalorimetry is a novel method that can rapidly detect microorganisms by their heat production. We investigated the accuracy and time to detec- tion of septic arthritis by using Microcalorimetry. Patients older than 18 years of age with acute arthritis of native joints were prospectively included. Synovial fluid was aspirated and investigated by Gram stain, culture and Microcalorimetry. The diagnosis of septic arthritis and non-septic arthritis were made byexperiencedrheumatologistsororthopaedicsurgeons.Sep- tic arthritis was diagnosed by considering the finding of acute arthritis together with findings such as positive Gram stain or positivecultureofsynovialfluidorpositivebloodculture.The sensitivity and specificity for diagnosing septic arthritis and the time topositivity ofMicrocalorimetryweredetermined.Of 90 patients (mean age 64 years), nine had septic arthritis, of whom four (44 %) had positive Gram stain, six (67 %) pos- itive synovial fluid culture and four (44 %) had positive blood culture. The sensitivity of Microcalorimetry was 89 %, the specificity was 99 % and the mean detection time was 5.0 h (range, 2.2-8.0 h). Microcalorimetry is an accurate and rapid method for the diagnosis of septic arthritis. It has potential to be used in clinical practice in diagnosing septic arthritis.
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Necrotizing Fasciitis After Breast Augmentation Rapid Microbiologic Detection by Using Sonication of Removed Implants and Microcalorimetry
American journal of clinical pathology, 2014Co-Authors: Erlangga Yusuf, Julia Steinrücken, Sophie Nordback, Andrej TrampuzAbstract:Objectives: To describe the use of sonication and Microcalorimetry in diagnosing necrotizing fasciitis in a 27-year-old woman with bilateral breast implants. Methods: The removed breast implants were subjected to sonication and Microcalorimetry. The Microcalorimetry findings were correlated with conventional microbiologic methods. The time to detection of infection was noted. Results: The patient had painful cellulitis of the right breast that enlarged within hours. Her C-reactive protein level was increased. Chest radiograph showed gas formation in the soft tissue lateral of the right breast. Surgery was performed: 300 mL (right breast) and 100 mL (left breast) of serous-purulent fluid were evacuated. Streptococcus pyogenes was cultured from the fluid 1 day after clinical presentation. Infection was diagnosed by Microcalorimetry of sonication fluid in 1 hour and 21 minutes. The Microcalorimetry curve from the right implant reached the peak earlier than did the left implant. Conclusion: Microcalorimetry will have a benefit in conditions in which rapid diagnosis of infection is important.
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isothermal Microcalorimetry a new tool to monitor drug action against trypanosoma brucei and plasmodium falciparum
PLOS Neglected Tropical Diseases, 2012Co-Authors: Tanja Wenzler, Andrea Steinhuber, Sergio Wittlin, Christian Scheurer, Reto Brun, Andrej TrampuzAbstract:Isothermal Microcalorimetry is an established tool to measure heat flow of physical, chemical or biological processes. The metabolism of viable cells produces heat, and if sufficient cells are present, their heat production can be assessed by this method. In this study, we investigated the heat flow of two medically important protozoans, Trypanosoma brucei rhodesiense and Plasmodium falciparum. Heat flow signals obtained for these pathogens allowed us to monitor parasite growth on a real-time basis as the signals correlated with the number of viable cells. To showcase the potential of Microcalorimetry for measuring drug action on pathogenic organisms, we tested the method with three antitrypanosomal drugs, melarsoprol, suramin and pentamidine and three antiplasmodial drugs, chloroquine, artemether and dihydroartemisinin, each at two concentrations on the respective parasite. With the real time measurement, inhibition was observed immediately by a reduced heat flow compared to that in untreated control samples. The onset of drug action, the degree of inhibition and the time to death of the parasite culture could conveniently be monitored over several days. Microcalorimetry is a valuable element to be added to the toolbox for drug discovery for protozoal diseases such as human African trypanosomiasis and malaria. The method could probably be adapted to other protozoan parasites, especially those growing extracellularly.
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Isothermal Microcalorimetry: a novel method for real-time determination of antifungal susceptibility of Aspergillus species
Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases, 2012Co-Authors: U. Furustrand Tafin, M. Clauss, Philippe M. Hauser, Jacques Bille, Jacques F. Meis, Andrej TrampuzAbstract:We evaluated Microcalorimetry for real-time susceptibility testing of Aspergillus spp. based on growth-related heat production. The minimal heat inhibitory concentration (MHIC) for A. fumigatus ATCC 204305 was 1 mg/L for amphotericin B, 0.25 mg/L for voriconazole, 0.06 mg/L for posaconazole, 0.125 mg/L for caspofungin and 0.03 mg/L for anidulafungin. Agreement within two 2-fold dilutions between MHIC (determined by Microcalorimetry) and MIC or MEC (determined by CLSI M38A) was 90% for amphotericin B, 100% for voriconazole, 90% for posaconazole and 70% for caspofungin. This proof-of-concept study demonstrated the potential of isothermal Microcalorimetry for growth evaluation of Aspergillus spp. and real-time antifungal susceptibility testing.
Ingemar Wadsö - One of the best experts on this subject based on the ideXlab platform.
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Isothermal Microcalorimetry in applied biology
Thermochimica Acta, 2002Co-Authors: Ingemar WadsöAbstract:Techniques of isothermal Microcalorimetry have been much improved during the past two decades. In addition to their use in fundamental research, applications of practical importance have been established in some areas. However, no significant use of isothermal Microcalorimetry has yet been seen in practical applications of biology, despite many methodological studies reported from that area. The main problem appears to be that the sample throughput of isothermal microcalorimeters is low compared to other techniques used in that field. Further, the non-specificity of calorimetric signals is in some cases a serious limitation. Significant progress has recently been made in the design of multi-channel isothermal microcalorimeters and in techniques where specific analytical methods have been combined with isothermal microcalorimeters. Some conclusions will be drawn with respect to the use of these techniques in applied work on living materials
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Standards in isothermal Microcalorimetry (IUPAC Technical Report)
Pure and Applied Chemistry, 2001Co-Authors: Ingemar Wadsö, Robert N. GoldbergAbstract:The main calorimetric principles used in isothermal Microcalorimetry are briefly discussed. Different chemical calibration and test reactions are discussed, with a focus on reactions suitable for ambient conditions: reactions initiated by mixing of liquids (including titration Microcalorimetry), dissolution of solid compounds and of slightly soluble gases, a photochemical process, and thermal power signals released over an extended period of time. Guidelines on the use of standardized chemical test and calibration reactions in isothermal Microcalorimetry are presented. A standardized terminology in reporting characteristics of isothermal microcalorimeters is proposed.
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trends in isothermal Microcalorimetry
Chemical Society Reviews, 1997Co-Authors: Ingemar WadsöAbstract:Isothermal microcalorimeters are of increasing importance in thermodynamics and as general ‘process monitors’. Recent developments in instrumentation and in experimental methods have been significant and several easy-to-use instruments are now commercially available. Important application areas include investigations of solute–solvent interactions and ligand binding processes, sorption processes, living cellular systems and the assessment of stabilities of technical products. The combination of isothermal calorimetry with different specific analytical techniques seems to be particularly promising.
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Isothermal Microcalorimetry for the characterization of interactions between drugs and biological materials
Thermochimica Acta, 1995Co-Authors: Ingemar WadsöAbstract:Abstract Studies of interactions between drugs and biological material form a broad application area for isothermal Microcalorimetry. Characterization of binding of drugs and related compounds to well-defined biological substances by use of titration Microcalorimetry is a very important area. This technique has now been taken into use in practical work (“rational drug design”) by several laboratories in the pharmaceutical industry. More fundamental studies of solute-solvent interactions for drugs and for simple model systems should be encouraged. Microcalorimetric techniques suitable for investigations of the effect of drugs on microorganisms and animal cellular systems have been much developed during recent years. However, few scientific groups are presently active in this field and it seems as if the technique has not yet been adopted by R&D laboratories in the pharmaceutical industry or in applied clinical work.
Alexander Bachmann - One of the best experts on this subject based on the ideXlab platform.
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microbial growth and isothermal Microcalorimetry growth models and their application to microcalorimetric data
Thermochimica Acta, 2013Co-Authors: Olivier Braissant, Gernot Bonkat, Dieter Wirz, Alexander BachmannAbstract:Abstract Over the last 10 years use of isothermal Microcalorimetry in the biological and biomedical field has been a increasing. Several biomedical applications such as detection and characterization of pathogens, drug testing, parasitology, and tissue engineering have been investigated. Similarly in environmental science isothermal Microcalorimetry has been shown to provide insight in soil science or in geomicrobiology. Often it is useful to convert the isothermal Microcalorimetry data into biologically meaningful data such as growth rate, lag phase, or maximum growth. In this study we review not only the various approaches used for such conversion but we also carefully look at the advantages, the drawbacks and underlying assumption of each approach. Understanding of these assumptions is a critical point into applying the right model to the right portion of the microcalorimetric data.
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Standardization of isothermal Microcalorimetry in urinary tract infection detection by using artificial urine
World journal of urology, 2012Co-Authors: Gernot Bonkat, Olivier Braissant, Malte Rieken, Anna Solokhina, Andreas F. Widmer, Reno Frei, Andre Van Der Merwe, Stephen Wyler, Thomas C. Gasser, Alexander BachmannAbstract:Purpose Isothermal Microcalorimetry (IMC) has recently been reported as a new method to rapidly detect urinary tract pathogens (UTP). However, further application of Microcalorimetry in the clinical setting requires a standardized procedure. An important step toward such standardization is to use a reproducible growth medium. In this study, we investigated the potential of artificial urine in combination with Microcalorimetry for detection of common UTP.
Graham Buckton - One of the best experts on this subject based on the ideXlab platform.
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Quantitative assessments of powder crystallinity: Estimates of heat and mass transfer to interpret isothermal Microcalorimetry data
Thermochimica Acta, 1998Co-Authors: Patricia Darcy, Graham BucktonAbstract:Abstract Isothermal Microcalorimetry is used to study small quantities of amorphous materials in crystalline powders. The aim of this work is to better understand the isothermal Microcalorimetry measurement with regard to the quantification of amorphous contents of materials. Amorphous lactose was crystallized in a sealed ampoule in an isothermal microcalorimeter at a range of temperatures (25–60°C) and humidities. Identical heat changes for crystallization were observed at all humidities at 25°C; however, the measured heat varied with humidity at higher temperatures. The heat measured by isothermal Microcalorimetry was approximately the difference between the heat of crystallization and the heat of vaporization of the desorbed water. The isothermal Microcalorimetry output for this process is now better understood and it can be seen that, in order to obtain quantitative data for crystallinity, it is necessary to have a slow supply of vapor. As the measured heat change is related to the extent of water desorption, care must be taken when using Microcalorimetry to quantify the amorphous content of powders, especially when comparing data generated at different environmental conditions.
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The use of isothermal Microcalorimetry in the study of small degrees of amorphous content of a hydrophobic powder
International Journal of Pharmaceutics, 1996Co-Authors: Humera Ahmed, Graham Buckton, David Alexander RawlinsAbstract:The crystallinity of a hydrophobic drug (L-365,260) has been investigated by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) and isothermal Microcalorimetry. The crystallinity was assessed in the isothermal microcalorimeter by taking a ratio of the responses seen when an unknown sample and an amorphous standard were exposed to ethanol vapour. It was found that large amounts of the material (up to 75%) became amorphous with protracted micronisation. The XRPD, DSC and isothermal Microcalorimetry methods could all be used to characterise the amorphous content for these highly disordered samples. When the drug was milled in a ball mill, considerably less of the sample mass became amorphous (less than 10% even for reasonably long milling times) and for such samples, only isothermal Microcalorimetry was a suitable technique for quantifying the degree of disorder as no difference was observed by use of DSC or XRPD for materials with up to 10% amorphous content. Microcalorimetry is a suitable approach for crystallinity studies on hydrophobic powders, giving a lower limit of detection for amorphous content that is in the order of 1% or less, which is well below that seen for XRPD.
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the use of isothermal Microcalorimetry in the study of changes in crystallinity induced during the processing of powders
International Journal of Pharmaceutics, 1994Co-Authors: Larserik Briggner, Graham Buckton, Katarina Bystrom, Patricia DarcyAbstract:Abstract Isothermal Microcalorimetry has been used to follow recrystallisation of amorphous regions of powder surfaces. Lactose monohydrate was taken as a model powder, and was processed by spray drying and micronisation. Spray drying produced an amorphous powder (as shown by X-ray diffraction), which was found to recrystallise when exposed to humidities over 50% RH. The recrystallisation process was extremely cooperative, with the entire sample recrystallising almost instantaneously, rather than a gradual process over the period of exposure to the water vapour. Similar results were noted when micronised material was investigated. The amount of amorphous material produced during micronisation was directly proportional to the intensity of the process. It proved possible to quantify the % amorphous content of powder sample with a resolution of at least 1%, which is considerably better than other techniques. The amorphous regions of the lactose crystallised as either α- or β-lactose. The difference between these samples could be detected by X-ray diffraction, and also could be seen by isothermal calorimetry, as the β-regions mutarotated to α-lactose. The application of isothermal Microcalorimetry to studies of crystal properties of powders provides a quantitative characterisation of many aspects of crystallinity and crystal transition. The data obtained can subsequently be used to characterise the properties of the material, and to show how and when crystallisation will occur, and to aid predictions of the product of the crystallisation process. The demonstration of these applications provides a huge potetential for the use of isothermal Microcalorimetry in this field of study.
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The applications of Microcalorimetry in the field of physical pharmacy
International Journal of Pharmaceutics, 1991Co-Authors: Graham Buckton, Anthony E. BeezerAbstract:Abstract The technique of Microcalorimetry is introduced, the instrumental output is shown to relate to thermodynamics, kinetics and the concentration of the reactants (analysis). The detection sensitivity of the instrument is discussed, with particular reference to possible application to isothermal stability testing of solid-state reactions in pharmaceuticals, at ambient conditions: this particular aspect is compared directly to the current practice of use of differential scanning calorimetry (DSC) to screen for excipient incompatibilities. It is necessary to raise the temperature of a reaction significantly to observe a response in a DSC that is detectable at ambient conditions in a microcalorimeter, thus the DSC experiment may give false conclusions if the reaction which occurs at elevated temperatures is not chemically identical to the reaction that proceeds under ambient conditions. Microcalorimetry detects all processes that occur in the reaction cell, this can have advantages in, for example, studies of mechanism, but can cause problems with regard to quantification, the experiment must often be designed to limit investigation to a specific process that is of interest. A selective literature review of applications is presented, which covers stability testing, studies of powder wettability (by immersion and adsorption), crystal properties, dissolution of tablets in artificial foodstuffs and aspects of drug targeting. These examples do not cover the full list of applications, but demonstrate that Microcalorimetry can be used to investigate any stage of the development, production and use of a dosage form, e.g. powder properties, excipient compatibility, product stability, tablet dissolution, direct in vitro studies of biological response etc.
Anthony E. Beezer - One of the best experts on this subject based on the ideXlab platform.
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The stability of benzoyl peroxide by isothermal Microcalorimetry.
International Journal of Pharmaceutics, 2001Co-Authors: F Zaman, Anthony E. Beezer, John C. Mitchell, Q Clarkson, J. Elliot, A.f Davis, Richard J. WillsonAbstract:Abstract Isothermal Microcalorimetry may be used to determine kinetic and thermodynamic parameters for chemical reactions. This paper reports rate constants, determined as a function of temperature, and the activation enthalpy for the degradation of solid benzoyl peroxide as determined by isothermal Microcalorimetry. Studies were conducted on aqueous suspension phase, solid benzoyl peroxide. In addition, supporting evidence is cited from work carried out in this laboratory on the solution phase degradation of benzoyl peroxide using UV-visible spectrophotometry. The activation energy obtained by Microcalorimetry was E a =137.8±6.6 kJ mol −1 and the activation energy obtained from UV-visible spectrophotometry was E a =112.7±4.2 kJ mol −1 .
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Pharmaceutical Microcalorimetry: applications to long-term stability studies.
International journal of pharmaceutics, 1999Co-Authors: Anthony E. Beezer, Richard J. Willson, Simon Gaisford, Andrew K. Hills, John C. MitchellAbstract:Calorimetry has been a mainstay of stability analyses for some time in the form of differential scanning Microcalorimetry (DSC). This technique exploits high (relatively) temperature studies of pure materials and of formulations to accelerate any degradation or interactions. The behaviour of the material at storage or ambient conditions is then estimated via extrapolation from the Arrhenius equation. Recent developments in isothermal Microcalorimetry allow the direct determination of both kinetic and thermodynamic parameters for long, slow reactions from studies conducted at appropriate temperatures and under designated environmental control (pH, pO2, RH etc.). This review introduces the kinetic analysis of microcalorimetric data and, through selected examples, shows applications of the method.
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Microcalorimetry in the screening of discovery compounds and in the investigation of novel drug delivery systems
Thermochimica Acta, 1995Co-Authors: Anthony E. Beezer, John C. Mitchell, Rachel M. Colegate, David J. Scally, Lance J. Twyman, Richard J. WillsonAbstract:Abstract Calorimetry has for some time been proposed as a rapid method for determination of bioactivity. This paper describes the background to this application and describes how it has been extended to the study of bioassay techniques via Microcalorimetry in the development of structure activity relationships (SARs). That SARs can be developed indicates that it is possible to guide drug synthetic strategy through the results of microcalorimetric investigations, and this approach is explored here. In an extension of this approach it is argued that Microcalorimetry is well suited to the examination of novel drug delivery systems, allowing investigation of the capacity of drug delivery molecules to release the drug in the presence of a target organism.
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Microcalorimetry and the Taylor—Aris method in the study of partition processes
Pesticide Science, 1992Co-Authors: Anthony E. Beezer, John C. Mitchell, David J. AndrewsAbstract:Microcalorimetry is introduced briefly and shown to permit the development of biologically based Structure Activity Relationships (SARs). These data can be related to the more conventionally used parameter, the partition coefficient. Further, calorimetric studies are shown to allow comparison of the partitioning properties of biological cells with solvents that are normally used in drug partitioning studies. The results indicate that more consideration should be given to partitioning into particulate, e.g. micellar and liposomal, solvent systems. The use of the Taylor-Aris dispersion broadening method is briefly introduced theoretically, and its practical exploitation is discussed. These two techniques, Microcalorimetry and the Taylor-Aris method are shown to allow new insights into partitioning systems and their application to biological SARs.
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The applications of Microcalorimetry in the field of physical pharmacy
International Journal of Pharmaceutics, 1991Co-Authors: Graham Buckton, Anthony E. BeezerAbstract:Abstract The technique of Microcalorimetry is introduced, the instrumental output is shown to relate to thermodynamics, kinetics and the concentration of the reactants (analysis). The detection sensitivity of the instrument is discussed, with particular reference to possible application to isothermal stability testing of solid-state reactions in pharmaceuticals, at ambient conditions: this particular aspect is compared directly to the current practice of use of differential scanning calorimetry (DSC) to screen for excipient incompatibilities. It is necessary to raise the temperature of a reaction significantly to observe a response in a DSC that is detectable at ambient conditions in a microcalorimeter, thus the DSC experiment may give false conclusions if the reaction which occurs at elevated temperatures is not chemically identical to the reaction that proceeds under ambient conditions. Microcalorimetry detects all processes that occur in the reaction cell, this can have advantages in, for example, studies of mechanism, but can cause problems with regard to quantification, the experiment must often be designed to limit investigation to a specific process that is of interest. A selective literature review of applications is presented, which covers stability testing, studies of powder wettability (by immersion and adsorption), crystal properties, dissolution of tablets in artificial foodstuffs and aspects of drug targeting. These examples do not cover the full list of applications, but demonstrate that Microcalorimetry can be used to investigate any stage of the development, production and use of a dosage form, e.g. powder properties, excipient compatibility, product stability, tablet dissolution, direct in vitro studies of biological response etc.