Lag Time Values Research Articles

Processing and properties of biodegradable compounds based on aliphatic polyesters

ABSTRACTTwo aliphatic biodegradable polyesters, Poly(butylene succinate) and Poly(lactic acid), are selected together with two inorganic fillers, talc and TiO2, to obtain biodegradable compounds for replacing polystyrene in the production of disposable plastic cups and plates. The rheological behavior of the pure polymers and the compounds is investigated, the mechanical properties of the compounds are determined in terms of modulus and elongation at break, the heat distortion temperature of the compounds is measured and compared to those of pure PBS and PS. Finally, the biodegradation of the compounds is also investigated. The processability and the final properties, in terms of elastic modulus and heat distortion temperature, make these compounds interesting for the production of disposable plates and cups for hot food and beverages, also considering that the elongation at break is significant. Furthermore, the results of biodegradation tests in composting conditions show that the presence of TiO2 induces a lag time and lower values of biodegradation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42481.

Growth Modelling of Listeria monocytogenes in Korean Pork Bulgogi Stored at Isothermal Conditions.

The purpose of this study was to develop predictive models for the growth of Listeria monocytogenes in pork Bulgogi at various storage temperatures. A two-strain mixture of L. monocytogenes (ATCC 15313 and isolated from pork Bulgogi) was inoculated on pork Bulgogi at 3 Log CFU/g. L. monocytogenes strains were enumerated using general plating method on Listeria selective medium. The inoculated samples were stored at 5, 15, and 25℃ for primary models. Primary models were developed using the Baranyi model equations, and the maximum specific growth rate was shown to be dependent on storage temperature. A secondary model of growth rate as a function of storage temperature was also developed. As the storage temperature increased, the lag time (LT) values decreased dramatically and the specific growth rate of L. monocytogenes increased. The mathematically predicted growth parameters were evaluated based on the modified bias factor (Bf), accuracy factor (Af), root mean square error (RMSE), coefficient of determination (R2), and relative errors (RE). These values indicated that the developed models were reliably able to predict the growth of L. monocytogenes in pork Bulgogi. Hence, the predictive models may be used to assess microbiological hygiene in the meat supply chain as a function of storage temperature.

Design of Chronomodulated Drug Delivery System of Valsartan: In Vitro Characterization.

The aim of the present study was to design and evaluate a chronomodulated time-clock pulsatile tablets of valsartan to release it after a certain lag time, independent of the gastrointestinal pH, in its absorption window to cope with the circadian rhythm of human body for blood pressure elevation. Core tablets were prepared by direct compression of a homogenous mixture of valsartan, Avicel PH101, croscarmellose sodium, magnesium stearate and Aerosil. The core tablets were then sprayed coated with a sealing layer formed of ethyl cellulose that was subsequently coated with a release-controlling layer. Three different aqueous dispersions namely; carnauba wax or beeswax or a mixture in a ratio of 2.5:1, respectively, were used to form five time-clock tablet formulations having the release controlling layer with different thickness {B5, B10, B20, BW5 and CW5}. Quality control testing were carried out to the core tablets. Differential scanning calorimetry was also performed to detect the possible drug excipient interaction in the core tablet formulation. The release was carried out, for the prepared time-clock tablet formulations, in 0.1 N hydrochloric acid for the first 2 h, followed by phosphate buffer (pH 6.8) for 4.5 h. The effect of pH on valsartan release was studied through a release study in 0.1 N hydrochloric acid for 6.5 h. Two phase dissolution study was performed to the selected time-clock tablet formulation to predict the drug permeation through the gastrointestinal tract. Stability study of the selected formula was performed at 25°/60% RH and at 40°/75% RH for 3 months. Results showed that a release-controlling layer composed of a mixture of carnauba wax and beeswax in a ratio of 2.5:1 showed a reasonable release lag time. The release lag time of the tablets increased with the increase of the coat thickness, thus B20>B10>B5 with corresponding lag time values of 4.5, 3 and 2.5 h, respectively. Selected B5 tablet formula exhibited a reasonable lag time after which the highest, complete % drug release at pH 6.8 was obtained. In addition, a good partitioning of valsartan, between the aqueous and organic phases in a ratio of 1:7, was observed. The selected formula was stable for at least 3 months under standard long-term and accelerated storage conditions. In conclusion, in vitro studies revealed that the novel time-clock system could be used successfully to deliver valsartan in a pulsatile pH-independent manner. It provided a desirable lag time followed by a rapid and complete drug release accompanied by an expected effective permeation through the biological membranes upon release in the duodenum; the window of absorption, as indicated by the two phase release study.

Site-Directed Pegylation of BDD FVIII (BAY 94-9027) Does Not Alter the Ability of the Molecule to Generate Thrombin, Activate Factor X or Become Inactivated By Activated Protein C

Introduction: BAY 94-9027 is a rationally designed B Domain Deleted (BDD) FVIII (Mei , B. et al Blood 2010). A single 60 kDa PEG molecule was attached to amino acids 1804 to increase its circulating half-life, reduce the exposure to epitopes reported to cause immunogenicity in the A3 domain (Shima M. Int. J. Haematol. 2006), while preserving full biological function. The PEGylation technology allows for an extended duration of action with the goal of reducing the number of infusions needed while maintaining protection from bleeds. In a recent clinical trial the molecule has shown significant efficacy for prophylactic treatment in hemophilia A patients (NCT01775618). The objective of this study was to further characterize in vitro BAY 94-9027 using Xase kinetics, activated protein C-dependent inactivation of FVIIIa, and thrombin generation assays.Methods and Results: Biochemical assays to determine apparent binding of the Factor IXa and Factor VIIIa complex and the Factor X activation kinetics revealed identical in vitro properties of BAY 94-9027 to the BDD FVIII comparator, Refacto AFÒ. The molecules also performed similarly in activated protein C (aPC) FVIIIa inactivation studies.BAY 94-9027 was further characterized by thrombin generation assay (TGA) in human hemophilic plasma. The TGAs were triggered using 1pM TF or 100pM XIa to simulate extrinsic and intrinsic activation. With XIa activation no differences were seen in peak thrombin, ETP or lag time between BDD FVIII and BAY 94-9027. The lag time, peak and ETP values also remained similar using TF activation. The XIa initiated TGA gives a more potent thrombin generation response compared to TF and is more sensitive to FVIII activity as judged by the left shift of the dose response curves. The TGAs were repeated while titrating thrombomodulin (TM) to generate aPC. Both BAY 94-9027 and BDD FVIII showed similar inactivation profile in the TM-TGA.Conclusion: The data demonstrates that the rationally designed site specific PEGylation of FVIII in BAY 94-9027 does not alter the in vitro coagulation properties, tested by the ability of BAY 94-9027 to generate thrombin, activate FX or inactivation by aPC. BAY 94-9027 represents the next generation of treatment in hemophilia, using PEGylation technology to reduce the number of infusions while maintaining FVIII activity. DisclosuresYegneswaran:Bayer Healthcare Pharmaceuticals: Employment. Jiang:Bayer Healthcare Pharmaceuticals: Employment. Yesantharao:Bayer Healthcare Pharmaceuticals: Employment. Kim:Bayer Healthcare Pharmaceuticals: Employment. Leong:Bayer Healthcare: Employment. Sim:Bayer Healthcare: Employment. Patel:Bayer Healthcare Pharmaceuticals: Employment. Kauser:Bayer Healthcare: Employment.

Effect of Packaging and Temperature on Survival Kinetics of Campylobacter jejuni on Precooked Chicken Breast

AbstractThe survival ability of Campylobacter jejuni in poultry has been a major public health risk because of the low infectious dose. The objective of this study was to investigate the effects of different packaging condition and temperature on the survival kinetics of C. jejuni ATCC 33291 on precooked chicken breast. Survival kinetics of C. jejuni were also compared with those of C. coli ATCC 43486. Inoculated chicken breasts with 5.0–6.0 log cfu/g were packed in three different ways (aerobic, semi‐aerobic or vacuum), which were stored at 4, 10, 17, 24, 30 and 36C. Survival curves were fitted to Baranyi model to obtain the values of lag time and death rate of C. jejuni. During storage, the greatest reduction of C. jejuni (4.316 log cfu/g) was observed in aerobic packaged chicken breast at 24C, while the least reduction of C. jejuni (1.031 log cfu/g) was observed in vacuum‐packaged chicken breast at 4C. Lag time was affected by packing method, temperature and strain. Similar survival behavior of C. coli to C. jejuni was observed only at 10C. At the temperatures above 24C, lag phase of C. jejuni was only observed in semi‐aerobic or vacuum‐packed chicken breasts, indicating that C. jejuni survived better than C. coli, for which no lag phase was observed. The results indicated that vacuum or semi‐aerobic packaging on poultry product at 4C, which is the most popular method at retail markets, created the highest risk for C. jejuni survival.Practical ApplicationsSurvival ability and pattern of Campylobacter in poultry product at retail market is affected by packing condition, storage temperature and species. The survival model for C. jejuni ATCC 33291 in precooked chicken was not suitable for use in making predictions for C. coli. ATCC 43486, thus the survival model for C. coli must be developed separately. The viable count of C. jejuni in tailing part in survival curve can be very dangerous, thus, preventing cross contamination and proper cooking must be reemphasized in the food service establishments and at home.

Predicting the gastrointestinal behaviour of modified-release products: Utility of a novel dynamic dissolution test apparatus involving the use of bicarbonate buffers

The establishment of physiologically relevant in vitro–in vivo correlations (IV–IVCs) is key for any biorelevant dissolution test. Historically, bicarbonate buffers have produced better correlations than compendial phosphate buffered media, though such tests are usually performed at a constant pH experiment, overlooking the notion that the pH of the luminal fluids is variable and fluctuating. In this work, we have devised a dynamic dissolution test method employing a physiological bicarbonate buffer under pH conditions of the proximal gut in order to assess the dissolution behaviour of various enteric polymer-coated (gastro-resistant) prednisolone tablets. The pH of the media is modulated and controlled by an Auto pH System™ which exploits the physiological equilibria between [H2CO3] and [HCO3−], to match it to the aboral change in pH with transit of the dosage form through the proximal small intestine (from pH 5.6 up to 6.8). The lag time values for an accelerated release and standard EUDRAGIT® L30D-55 coated formulation (25min and 60min, respectively) were close to the previously reported initial tablet disintegration time data obtained in-vivo by γ-scintigraphy (28min and 66min, respectively). Dissolution of alternative delayed release coated products was also better discriminated in the dynamic buffer system. These data confirm the dynamic dissolution system provides a robust and reliable platform to predict the in vivo fate of oral products in a laboratory setting.

Discrete‐Storm Water‐Table Fluctuation Method to Estimate Episodic Recharge

We have developed a method to identify and quantify recharge episodes, along with their associated infiltration-related inputs, by a consistent, systematic procedure. Our algorithm partitions a time series of water levels into discrete recharge episodes and intervals of no episodic recharge. It correlates each recharge episode with a specific interval of rainfall, so storm characteristics such as intensity and duration can be associated with the amount of recharge that results. To be useful in humid climates, the algorithm evaluates the separability of events, so that those whose recharge cannot be associated with a single storm can be appropriately lumped together. Elements of this method that are subject to subjectivity in the application of hydrologic judgment are values of lag time, fluctuation tolerance, and master recession parameters. Because these are determined once for a given site, they do not contribute subjective influences affecting episode-to-episode comparisons. By centralizing the elements requiring scientific judgment, our method facilitates such comparisons by keeping the most subjective elements openly apparent, making it easy to maintain consistency. If applied to a period of data long enough to include recharge episodes with broadly diverse characteristics, the method has value for predicting how climatic alterations in the distribution of storm intensities and seasonal duration may affect recharge.

High coagulation factor levels and low protein C levels contribute to enhanced thrombin generation in patients with diabetes who do not have macrovascular complications

AimsA prothrombotic state characterized by activation of the coagulation system has been implicated in the pathogenesis of vascular complications in diabetes mellitus. Recently, a thrombin generation assay was introduced as a laboratory assessment of global hemostatic potential. We used this thrombin generation assay to investigate global hemostatic potential in patients with diabetes who did not have macrovascular complications. MethodsThis study was a prospective case–control study comparing 89 patients with diabetes with 49 healthy controls. The thrombin generation assay was conducted with the calibrated automated thrombogram using tissue factor with or without the addition of thrombomodulin, giving values for lag time, endogenous thrombin potential, and peak thrombin. ResultsPatients with diabetes showed hypercoagulability, as detected by the thrombin generation assay, compared with healthy controls. Correspondingly, high levels of coagulation factors (II, V, VII, VIII, and X) and low levels of anticoagulant (protein C) were major contributing factors in this hypercoagulability. Interestingly, a high blood glucose level was correlated with shortened clotting time, reflecting the association between hyperglycemia and hypercoagulability. Patients who were taking statins or angiotensin receptor blockers showed decreased endogenous thrombin potential ratio and increased protein C levels, suggesting relative hypocoagulability. ConclusionsPatients with diabetes showed hypercoagulability, high levels of coagulation factors, and low levels of protein C. Further study is required to investigate how this hemostatic potential may be used to guide physicians toward more effective management of hemostatic complications.

Levels of human erythrocyte membrane-bound and cytosolic glycohydrolases are associated with oxidative stress in erectile dysfunction patients.

Oxidative stress (OS) and production of NO, by endothelium nitric oxide synthetase (eNOS), are involved in the pathophysiology of erectile dysfunction (ED). Moreover, OS induces modifications of the physicochemical properties of erythrocyte (RBC) plasma membranes and of the enzyme content of the same membranes. Due to their role in signalling early membrane alterations in OS-related pathologies, several plasma membrane and cytosolic glycohydrolases of human RBC have been proposed as new markers of cellular OS. In RBC, NOS can be activated and deactivated by phosphorylation/glycosylation. In this regulatory mechanism O-β-N-AcetylGlucosaminidase is a key enzyme. Cellular levels of O-GlcNAcylated proteins are related to OS; consequently dysfunctional eNOS O-GlcNAcylation seems to have a crucial role in ED. To elucidate the possible association between RBC glycohydrolases and OS, plasma hydroperoxides and antioxidant total defenses (Lag-time), cytosolic O-β-N-AcetylGlucosaminidase, cytosolic and membrane Hexosaminidase, membrane β-D-Glucuronidase, and α-D-Glucosidase have been studied in 39 ED patients and 30 controls. In ED subjects hydroperoxides and plasma membrane glycohydrolases activities are significantly increased whereas Lag-time values and cytosolic glycohydrolases activities are significantly decreased. These data confirm the strong OS status in ED patients, the role of the studied glycohydrolases as early OS biomarker and suggest their possible use as specific marker of ED patients, particularly in those undergoing nutritional/pharmacological antioxidant therapy.

Predictive modeling of Staphylococcus aureus growth on Gwamegi (semidry Pacific saury) as a function of temperature

Gwamegi (semidry Pacific saury [Cololabis saira]) is a Korean food made by a traditional method of repeated freezing and de-freezing during winter. The present study aimed at developing predictive modeling of S. aureus growth on Gwamegi as a function of temperature (10–35°C). Modified Gompertz, Baranyi, and logistic primary models were fitted to experimental values. Polynomial quadratic, nonlinear Arrhenius and square root models were selected as secondary models and analyzed using specific growth rate (μmax) and lag time (λ) values obtained from the primary models. Based on the optimized models derived from the Baranyi and square root equations for μmax, its r 2 and mean square error (MSE) were 0.991 and 0.00058, and bias factor (B f) and accuracy factor (A f) were 1.0087 and 1.0801, respectively. The logistic and polynomial quadratic equations for λ, its r 2 and MSE were 0.989 and 0.22834, B f and A f were 0.9742 and 1.0271, respectively. These predictive models can provide basic information for quantitative microbial risk assessment of Gwamegi and other processed semidried seafood.

Predictive model for growth of Staphylococcus aureus in blanched spinach with seasoning

The safe storage time of blanched spinach with seasoning was determined using a predictive model of Staphylococcus aureus as a function of storage temperatures (5, 15, 20, 25, 30, 35°C). Storage of blanched spinach with seasoning at 5 and 15°C did not show any appreciable increase in the viable populations of S. aureus. At 20, 25, 30, and 35°C, a progressive increase in the viable populations of S. aureus was observed and increased more rapidly at 30 and 35dgC. A primary model (Gompertz model) was used to determine the determination coefficient (R2) values of lag time (LT) and specific growth rate (SGR). R2 values were not detected (ND) (5°C), 0.9777 (15°C), 0.9980 (20°C), 0.9949 (25°C), 0.9940 (30°C), and 0.9959 (35°C). A quadratic polynomial model equation could be proposed as a secondary model and was applied for lag time and SGR from primary modeling graphed as a function of storage temperature. The compatibility of the model was confirmed by calculating R2, mean square error (MSE), bias factor (Af), and accuracy factor (Bf) values as static parameters. For LT and SGR, R2 values were 0.9718 and 0.9789; MSE. 3.25 and 0.00; Af. 1.19 and 1.12; Bf, 1.05 and 1.02, respectively. These results indicate that the predictive model for S. aureus on blanched spinach with seasoning has a high statistical compatibility. Predicting S. aureus growth under different temperature storage conditions yielded safe storage times of blanched spinach with seasoning of 10, 10, 8, and 6 h for storage temperatures of 20, 25, 30, and 35°C, respectively.

F2Cor: fast 2-stage correlation algorithm for FCS and DLS

We present a new multiple-tau correlation algorithm which is the fastest to date. The resulting curve is identical to that obtained with the conventional multiple-tau algorithm, but the calculation time is much shorter. It combines two approaches. For short values of the lag-time a very simple correlation histogram is used, while for higher lag-time values the traditional multiple-tau bin-and-multiply approach is used. The lag-time limit between these two stages depends on the count rate. The computation time scales linearly with the count rate and is as fast as 0.1 µs/photon.

Thrombin Generation Assay and by-Passing Therapies in Patients with Inhibitors,

Abstract 3322No routine test is available for monitoring bypassing agent therapy in patients with inhibitors. General clotting tests such as PT, aPTT and factor activities do not reflect overall thrombin generation and are insensitive to hypercoagulation and hypocoagulation.In this study, we aimed to investigate the importance of thrombin generation assay (TGA) in monitoring hemostasis during factor supplementation in hemophilia patients with and without inhibitor. Study group consisted of 39 patients (27 hemophilia A, 8 hemophilia B, one vWD-3, two FVII def. and one FX def.). All patients were male. Seven out of 27 hemophilia A patients had an inhibitor. The mean age was 17±9.7 years (range: 3–55). A total of 59 (inhibitor positive=19) bleeding episodes and/or surgical interventions were evaluated. Acute bleeding episodes were classified as acute hemarthrosis (n=21), soft tissue hemorrhages (n=6), oral /nasal hemorrhages (n=7), hematuria (n=2) or GIT hemorrhages (n=3). Twenty major or minor surgical interventions were classified as radioisotope synovectomy (n=11), teeth extractions (n=2), circumcision (n=1), port-a-cath removal (n=1); hemorrhoid operation (n=1) or open synovectomy and arthroplasty n=4). rFVIIa and aPCC therapies were administered to inhibitor-positive patients. PPP was always prepared within 30 min of venipuncture. PT, aPTT and FVIII activities were measured in plasma from citrated blood samples taken before treatment of patients for bleeding or for surgery preparation. Before TGA test, aliquoted PPP was stored for 3 months at −80°C, and all samples were assessed together. Lab parameters were evaluated at basal levels and after 1 hour of factor therapy. These tests were repeated when clinical hemostasis was obtained within 24 hours of the post-op period. PT, aPTT, FVIII activities were assessed by Siemens kits with CA-1500 (Sysmex–Siemens). The Calibrated Automated Thrombogram (CAT; Thrombinoscope BV, Maastricht, The Netherlands) method was used for the TGA.No difference was found between 1th and 24th hour clinical responses after rFVIIa and aPCC treatment (P= 0.96) in hemophilic patients with inhibitor. Basal, first hour and 24th hour TGA lag time values were significantly shorter in hemophilic patients with inhibitor than in inhibitor-free patients (P= <.01). Basal TGA parameters (ETP, peak thrombin height, and time to peak values were significantly better in hemophilic patients without inhibitor than in those with inhibitor (P= <.01). No difference was found between the first hour and 24th hour TGA parameter values between hemophilic patients without/with inhibitor after factor therapy. TGA lag time values measured 24 hours post-event were significantly shorter in rFVIIa than aPCC treatment in hemophilic patients with inhibitor (P=.04). First hour ETP and first hour and 24 hour peak thrombin height were significantly higher in aPCC than rFVIIa treatment in hemophilic patients with inhibitor (P=.01). First hour TEG parameter (R, K and alpha angle degree) values were found significantly in aPCC (12 episodes)than rFVIIa treatment (7 episodes) (P=.03). First hour and 24th hour INR values were significantly shorter in rFVIIa than aPCC (P= <.01). No association was found between first hour clinical responses and TGA parameters after inhibitor bypassing agent treatment. In this study, before and after bleeding episode treatment/surgery prophylaxis, basal, 1st and 2–24th hours lag time values of inhibitor-positive patients were significantly smaller than inhibitor-negative patients. Basal TGA parameters such as ETP, peak thrombin height, and time to peak thrombin values of hemophilic patients without inhibitor were significantly better than those of hemophilic patients with inhibitor. When hemophilic patients with or without inhibitor were evaluated for accurate clinic responses at 24 hours after factor replacement treatment, the clinical response was significantly better in the inhibitor-negative group. As a conclusion, for monitoring hemostasis in inhibitor patients related severe bleeding and major operations, TGA test may be used for most rational using of by-passing therapies. Disclosures:Kavakli:NovoNordisk: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Baxter: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

The Antioxidant Activity and Thermal Stability of Lemon Verbena (Aloysia triphylla) Infusion

Because of its good sensorial attributes, lemon verbena is used as a primary ingredient in infusions and nonalcoholic drinks. The present study was designed to assess the antioxidant activity (AA) of lemon verbena infusion (LVI) as well as the thermal stability of its AA and the content of polyphenolic compounds. The values reflecting the AA of LVI, including AA index, fast scavenging rate against 2,2-diphenyl-1-picrylhydrazyl, Trolox equivalent antioxidant capacity, and hydroxyl radical scavenging, are higher than those of many herbal infusions and antioxidant drinks estimated from reported data. In addition, the slope lag time and specific oxyradical antioxidant capacity values of LVI are comparable to those of a commercial antioxidant drink based on green tea. Hence, LVI is a source of bifunctional antioxidants, and thus in vivo studies of the antioxidant capacity of LVI would be useful to evaluate its potential as an ingredient in antioxidant drinks.

Effect of grinding on in vitro floating behaviour of effervescent matrix tablets of ciprofloxacin hydrochloride: Negative impact on initial buoyancy

The purpose of this study was to form dispersion of sodium bicarbonate in hydroxyl-propyl methyl cellulose (HPMC K4M) matrix and investigate its impact on in vitro floating behaviour and drug release. The dispersion of sodium bicarbonate in HPMC K4M was achieved by grinding method using mortar and pestle. The in vitro floating behaviour and drug release of matrix tablets having grinding dispersion (GD) were compared with matrix tablets having physical mixture. The GD matrix tablets were having higher values of buoyancy lag time (BLT) in comparison to PM matrix tablets. However, the floating duration of GD matrix tablets was higher than that for PM matrix tablets. The swelling extent was also found higher for GD matrix tablets. Higher drug release rate was achieved with GD matrix tablets and drug release kinetics was explained by korsemeyer-peppas model. The values of diffusion coefficient (n) were found between 0.45−0.89, which indicates the anomalous type of drug transport.

A thrombin generation assay may reduce the need for compression ultrasonography for the exclusion of deep venous thrombosis in the elderly

Introduction. The exclusion of deep venous thrombosis (DVT) by pre-test probability (PTP) and D-dimer in the elderly is safe, but has a low specificity. There is increasing interest in the diagnostic role of thrombin generation in patients with thrombosis. We evaluated the value of thrombin generation in the exclusion of DVT, especially in elderly patients. Material and methods. All thrombin generation parameters of the Endogenous Thrombin Potential assay were tested retrospectively in a cohort of 443 patients suspected for DVT. The performance of the assay was calculated as AUC of the ROC curve and association with DVT as odds ratio (OR). The lag time value was combined with results of PTP and Innovance D-dimer assay. Results. All thrombin generation parameters had a low AUC. In the 4th age quartile, the corrected OR of lag time increased to 16 and the AUC of lag time for the combination PTP < 2 and D-dimers ≥ 500 μg/L was 0.96 with a cut-off value of 23.0 sec. The exclusion of DVT in patients ≥ 75 years (n = 30), based on this combination and lag time values ≤ 23.0 sec had a NPV of 100% and a specificity of 96.0% in this subgroup of patients and decreased the number needed to test from 10 to 1.1. Conclusion. Thrombin generation parameters alone are inappropriate for the exclusion of DVT. However, in the elderly, the current algorithm of exclusion of DVT may improve markedly by the addition of the lag time results of the ETP.

Development of Predictive Growth Models for Staphylococcus aureus and Bacillus cereus on Various Food Matrices Consisting of Ready-to-Eat (RTE) Foods

We developed predictive growth models for Staphylococcus aureus and Bacillus cereus on various food matrices consisting primarily of ready-to-eat (RTE) foods. A cocktail of three S. aureus strains, producing enterotoxins A, C, and D, or a B. cereus strain, were inoculated on sliced bread, cooked rice, boiled Chinese noodles, boiled bean sprouts, tofu, baked fish, smoked chicken, and baked hamburger patties at an initial concentration of 3 log CFU/g and stored at 8, 10, 13, 17, 24, and <TEX>$30^{\circ}C$</TEX>. Growth kinetic parameters were determined by the Gompertz equation. The square-root and Davey models were used to determine specific growth rate and lag time values, respectively, as a function of temperature. Model performance was evaluated based on bias and accuracy factors. S. aureus and B. cereus growth were most delayed on sliced bread. Overall, S. aureus growth was significantly (p<0.05) more rapid on animal protein foods than carbohydrate-based foods and vegetable protein foods. The fastest growth of S. aureus was observed on smoked chicken. B. cereus growth was not observed at 8 and <TEX>$10^{\circ}C$</TEX>. B. cereus growth was significantly (p<0.05) more rapid on vegetable protein foods than on carbohydrate-based foods. The secondary models developed in this study showed suitable performance for predicting the growth of S. aureus and B. cereus on various food matrices consisting of RTE foods.

수육에서의 Staphylococcus aureus 성장 예측모델

Cooked pork can be easily contaminated with Staphylococcus aureus during carriage and serving after cooking. This study was performed to develop growth prediction models of S. aureus to assure the safety of cooked pork. The Baranyi and Gompertz primary predictive models were compared. These growth models for S. aureus in cooked pork were developed at storage temperatures of 5, 15, and 25 C. The specific growth rate (SGR) and lag time (LT) values were calculated. The Baranyi model, which displayed a R of 0.98 and root mean square error (RMSE) of 0.27, was more compatible than the Gompertz model, which displayed 0.84 in both R and RMSE. The Baranyi model was used to develop a response surface secondary model to indicate changes of LT and SGR values according to storage temperature. The compatibility of the developed model was confirmed by calculating R , B , A , and RMSE values as statistic parameters. At 5, 15 and 25 C, R was 0.88, 0.99 and 0.99; RMSE was 0.11, 0.24 and 0.10; B was 1.12, 1.02 and 1.03; and A was 1.17, 1.03 and 1.03, respectively. The developed predictive growth model is suitable to predict the growth of S. aureus in cooked pork, and so has potential in the .microbial risk assessment as an input value or model.

Comparison of Two Optical-Density-Based Methods and a Plate Count Method for Estimation of Growth Parameters of Bacillus cereus

Quantitative microbiological models predicting proliferation of microorganisms relevant for food safety and/or food stability are useful tools to limit the need for generation of biological data through challenge testing and shelf-life testing. The use of these models requires quick and reliable methods for the generation of growth data and estimation of growth parameters. Growth parameter estimation can be achieved using methods based on plate counting and methods based on measuring the optical density. This research compares the plate count method with two optical density methods, namely, the 2-fold dilution (2FD) method and the relative rate to detection (RRD) method. For model organism Bacillus cereus F4810/72, the plate count method and both optical density methods gave comparable estimates for key growth parameters. Values for the maximum specific growth rate (mu(max)) derived by the 2FD method and by the RRD method were of the same order of magnitude, but some marked differences between the two approaches were apparent. Whereas the 2FD method allowed the derivation of values for lag time (lambda) from the data, this was not possible with the RRD method. However, the RRD method gave many more data points per experiment and also gave more data points close to the growth boundary. This research shows that all three proposed methods can be used for parameter estimation but that the choice of method depends on the objectives of the research.

Constantly stirred sorbent and continuous flow integrative sampler: New integrative samplers for the time weighted average water monitoring

Two innovative integrative samplers have been developed enabling high sampling rates unaffected by turbulences (thus avoiding the use of performance reference compounds) and with negligible lag time values. The first, called the constantly stirred sorbent (CSS) consists of a rotator head that holds the sorbent. The rotation speed given to the head generates a constant turbulence around the sorbent making it independent of the external hydrodynamics. The second, called the continuous flow integrative sampler (CFIS) consists of a small peristaltic pump which produces a constant flow through a glass cell. The sorbent is located inside this cell. Although different sorbents can be used, poly(dimethylsiloxane) PDMS under the commercial twister format (typically used for stir bar sorptive extraction) was evaluated for the sampling of six polycyclic aromatic hydrocarbons and three organochlorine pesticides. These new devices have many analogies with passive samplers but cannot truly be defined as such since they need a small energy supply of around 0.5 W supplied by a battery. Sampling rates from 181 × 10 −3 to 791 × 10 −3 L/day were obtained with CSS and 18 × 10 −3 to 53 × 10 −3 with CFIS. Limits of detection for these devices are in the range from 0.3 to 544 pg/L with a precision below 20%. An in field evaluation for both devices was carried out for a 5 days sampling period in the outlet of a waste water treatment plant with comparable results to those obtained with a classical sampling method.