Modelling biofilm formation of Salmonella enterica ser. Newport as a function of pH and water activity

The effect of pH and water activity (aw) on the formation of biofilm by Salmonella enterica ser. Newport, previously identified as a strong biofilm producer, was assessed. Biofilm formation was evaluated in tryptone soy broth at 37 C and at different combinations of pH (3.3e7.8) and aw (0.894e0.997). In total, 540 biofilm formation tests in 108 pH and aw combinations were carried out in polystyrene microtiter plates using crystal violet staining and optical density (OD; 580 nm) measurements. Since the individual effects of pH and aw on biofilm formation had a similar pattern to that observed for microbial growth rate, cardinal parameter models (CPMs) were used to describe these effects. CPMs described successfully the effects of these two environmental parameters, with the estimated cardinal values of pHmin, pHopt, pHmax, awmin and awopt being 3.58, 6.02, 9.71, 0.894 and 0.994, respectively. The CPMs assumption of the multiplicative inhibitory effect of environmental factors was validated in the case of biofilm formation using additional independent data (i.e. 430 OD data at 86 different combinations of pH and aw). The validation results showed a good agreement (r2 ¼ 0.938) between observed and predicted OD with no systematic error. In the second part of this study, a probabilistic model predicting the pathogen's biofilm formation boundaries was developed, and the degree of agreement between predicted probabilities and observations was as high as 99.8%. Hence, the effect of environmental parameters on biofilm formation can be quantitatively expressed using mathematical models, with the latter models, in turn, providing useful information for biofilm control in food industry environments

Kinetics of osmotic processing of beef meat and impact on its safety and quality

Osmotic dehydration is a mild process used in several foods, aiming to remove water from the food matrix. The objective of the present PhD thesis was to study the osmotic processing of beef meat and the impact of process parameters on the mass transfer phenomena and on the quality characteristics and shelf-life of meat. The first part of this research focused on the assessment of binary (salt and water) and ternary (maltodextrin, salt and water) osmotic solutions, as well as the effect of process parameters (osmotic solution concentration, temperature, time, agitation) on mass transfer phenomena. The results showed that the use of ternary osmotic solutions led to similar water loss compared to binary solutions, while solids gain, and especially salt uptake, was reduced. The use of maltodextrin solutions can produce the desirable mass transfer phenomena (higher water loss and lower solids gain and salt uptake) during osmotic processing. Various mathematical models (diffusion, Peleg, Azuara and Hawkes and Flink) were used in order to describe the mass transfer phenomena, demonstrating a good fit to experimental data. The diffusion and the Peleg models exhibited a better fit, with the latter producing slightly better results. Moving to the second part of the study, meat shrinkage during osmotic processing was evaluated. A mathematical model was developed in order to predict meat volume changes as a function of water loss and osmotic solution concentration. The proposed model allows for the calculation of meat volume reduction during processing without requiring further measurements. Furthermore, the experimental data were used for a more accurate prediction of diffusion coefficients. As the results demonstrated, the moisture diffusion coefficients were overestimated when the sample dimensions were assumed to be constant. In the third part of the study, the addition of liquid smoke to the osmotic solution and its effect on mass transfer phenomena, on the quality, the sensory characteristics and on the shelf life of meat was evaluated. The addition of liquid smoke did not, in most cases, affect the mass transfer phenomena, but it had a significant impact on product quality and sensory characteristics. Osmotic dehydration delayed microbial growth during refrigerated storage of meat, increasing the shelf life by at least two days. The addition of liquid smoke to the osmotic solution further increased the shelf life of the treated samples with respect to microbial growth, while it inhibited lipid oxidation, providing oxidative stability throughout the storage period, even in the case of osmotic processing with sodium chloride solutions. Finally, an attempt to investigate the changes in the structure of muscle cells at low temperatures, directly affecting mass transfer phenomena, took place. The results of the present study have led to the clarification of some important questions about the osmotic processing of meat, providing a more comprehensive picture of the process.Η ωσμωτική αφυδάτωση αποτελεί μία ήπια επεξεργασία που εφαρμόζεται σε διάφορα τρόφιμα στοχεύοντας στην απομάκρυνση νερού από το εσωτερικό του τροφίμου. Το βασικό αντικείμενο της παρούσας διδακτορικής διατριβής ήταν η μελέτη της ωσμωτικής επεξεργασίας μοσχαρίσιου κρέατος και της επίδρασης των παραμέτρων της διεργασίας στην κινητική της μεταφοράς μάζας, καθώς και στα ποιοτικά χαρακτηριστικά και τη διάρκεια ζωής του παραγόμενου προϊόντος. Το πρώτο μέρος της έρευνας επικεντρώθηκε στην αξιολόγηση της επίδρασης διμερών (άλας και νερό) και τριμερών (μαλτοδεξτρίνη, άλας και νερό) ωσμωτικών διαλυμάτων, καθώς και των συνθηκών επεξεργασίας (συγκέντρωση ωσμωτικού διαλύματος, θερμοκρασία, χρόνος, εφαρμογή ανάδευσης) στα φαινόμενα μεταφοράς μάζας. Τα αποτελέσματα έδειξαν ότι η χρήση τριμερών διαλυμάτων οδήγησε σε παρόμοια απώλεια υγρασίας σε σύγκριση με τη χρήση των διμερών, με ταυτόχρονη μείωση της πρόσληψης στερεών και συγκεκριμένα χλωριούχου νατρίου. Ως εκ τούτου, συμπεραίνεται ότι η χρήση μαλτοδεξτρίνης ως ωσμωτικό μέσο μπορεί να επιφέρει τα επιθυμητά φαινόμενα μεταφοράς μάζας (αυξημένη απώλεια υγρασίας και μειωμένη πρόσληψη στερεών και χλωριούχου νατρίου). Ακολούθησε περιγραφή της κινητικής, χρησιμοποιώντας διάφορα μαθηματικά μοντέλα (μοντέλο διάχυσης, Peleg, Azuara και Hawkes and Flink) τα οποία παρουσίασαν ικανοποιητική προσαρμογή στα πειραματικά δεδομένα. Η καλύτερη προσαρμογή παρατηρήθηκε από το μοντέλο της διάχυσης και το μοντέλο του Peleg, με το δεύτερο να δίνει ελαφρώς καλύτερα αποτελέσματα. Στο δεύτερο μέρος της έρευνας μελετήθηκε και ποσοτικοποιήθηκε η συρρίκνωση του κρέατος κατά την ωσμωτική επεξεργασία. Αναπτύχθηκε ένα μαθηματικό μοντέλο πρόβλεψης της μείωσης του όγκου του κρέατος ως συνάρτηση της απώλειας υγρασίας και της συγκέντρωσης του ωσμωτικού διαλύματος. Με το προτεινόμενο μοντέλο μπορεί να υπολογιστεί το ποσοστό της συρρίκνωσης κατά την επεξεργασία χωρίς να απαιτείται ξεχωριστή αξιολόγηση και μέτρηση της ίδιας της παραμέτρου. Επιπροσθέτως, τα δεδομένα της συρρίκνωσης χρησιμοποιήθηκαν για την ορθότερη πρόβλεψη των συντελεστών διάχυσης, καθώς όπως έδειξαν τα αποτελέσματα οι τιμές των συντελεστών διάχυσης της υγρασίας υπερεκτιμούνται όταν οι διαστάσεις των δειγμάτων θεωρούνται αμετάβλητες. Το τρίτο μέρος της έρευνας επικεντρώθηκε στη μελέτη της προσθήκης υγρού καπνού στο ωσμωτικό διάλυμα και η επίδρασή του στα φαινόμενα μεταφοράς μάζας, στα ποιοτικά και οργανοληπτικά χαρακτηριστικά του προϊόντος και στη μετέπειτα διάρκεια ζωής του. Η προσθήκη υγρού καπνού δεν επηρέασε, στις περισσότερες περιπτώσεις, τα φαινόμενα μεταφοράς μάζας, ωστόσο είχε σημαντική επίδραση στα ποιοτικά και οργανοληπτικά χαρακτηριστικά του παραγόμενου προϊόντος. Η διεργασία της ωσμωτικής επεξεργασίας καθυστέρησε την μικροβιακή ανάπτυξη κατά τη συντήρηση των δειγμάτων σε θερμοκρασίες ψύξης, αυξάνοντας τη διάρκεια ζωής του κρέατος κατά τουλάχιστον δύο ημέρες. Η προσθήκη υγρού καπνού στο ωσμωτικό διάλυμα αύξησε ελαφρώς περισσότερο τη διάρκεια ζωής του επεξεργασμένου κρέατος αναφορικά με τη μικροβιακή ανάπτυξη, ενώ είχε ως αποτέλεσμα την αναστολή της οξείδωσης, παρέχοντας οξειδωτική σταθερότητα καθ’ όλη τη διάρκεια της συντήρησής του, ακόμη και στην περίπτωση ωσμωτικής επεξεργασίας με διαλύματα χλωριούχου νατρίου. Τέλος, στη παρούσα έρευνα πραγματοποιήθηκε προσπάθεια διερεύνησης των μεταβολών που υφίσταται η δομή των μυϊκών κυττάρων σε χαμηλές θερμοκρασίες επηρεάζοντας άμεσα το συνολικό φαινόμενο της ώσμωσης. Τα αποτελέσματα της παρούσας έρευνας οδήγησαν στην αποσαφήνιση ορισμένων σημαντικών ερωτημάτων σχετικά με την ωσμωτική επεξεργασία του κρέατος, παρέχοντας μία συνολική εικόνα της επεξεργασίας

Application of UV–Vis spectroscopy for the detection of adulteration in Mediterranean honeys

The present study aimed to identify adulteration of honey with sugar syrups and colorants using UV–Vis spectroscopy, combined with multivariate statistical analysis. A total of 209 honeys were used, including 151 commercial honey samples (thyme, pine, and polyfloral honeys) collected from different countries of Mediterranean (Greece, Malta, Spain, Tunisia, and Turkey) and 58 adulterated Greek thyme honey samples by adding syrups and colorants. Honey adulteration was identified using Principal Component Analysis (PCA) along with Random Forest (RF), Partial Least Squares – Discriminant Analysis (PLS-DA), and Data Driven-Soft Independent Modelling of Class Analogies (DD-SIMCA) using the spectral range of 220–550 nm. Comparatively, DD-SIMCA models produced better results in terms of accuracy and sensitivity in most cases evaluated. The results support the good predictive capability of UV–Vis spectroscopy combined with chemometrics for the determination of honey adulteration, and thus, it could be utilized as a rapid, inexpensive, and simple method.</p

Greek Remdesivir Cohort (GREC) Study: Effectiveness of Antiviral Drug Remdesivir in Hospitalized Patients with COVID-19 Pneumonia

In several randomized studies, remdesivir (RDV) has been reported to shorten the recovery period and improve clinical outcomes in COVID-19 patients, and thus, it is recommended as a standard of care. Nevertheless, controversial reports have been published. The aim of the present study is to evaluate the effectiveness of remdesivir in hospitalized patients with COVID-19 pneumonia at three Greek University Departments of Infectious Diseases with homogenous treatment protocols. From September 2020 to February 2021, we retrospectively analyzed adults hospitalized with confirmed SARS-CoV-2 infection and radiological findings of pneumonia, who received remdesivir once daily for five days. Exploratory end points were duration of hospitalization, time of intubation, and death. Overall, 551 patients were included in the study. The optimal cutoff point for the number of days needed after symptom initiation for drug administration associated with better clinical outcome was 7 days. Higher odds for discharge and lower for intubation were observed in patients with treatment initiation &le;7 days (p = 0.052 and p = 0.019, retrospectively) regardless of gender (p = 0.537), hypertension (p = 0.096), dyslipidemia (p = 0.221), diabetes mellitus (p = 0.306), and usage of immunomodulators (p = 0.408). Our study has demonstrated beneficial effects of early treatment with remdesivir (&le;7 days from symptom onset) on rates of intubation and probability of discharge

Intensive-Dose Tinzaparin in Hospitalized COVID-19 Patients: The INTERACT Study

(1) Background: It is well-established that coronavirus disease-2019 (COVID-19) is highly pro-inflammatory, leading to activation of the coagulation cascade. COVID-19-induced hypercoagulability is associated with adverse outcomes and mortality. Current guidelines recommend that hospitalized COVID-19 patients should receive pharmacological prophylaxis against venous thromboembolism (VTE). (2) INTERACT is a retrospective, phase IV, observational cohort study aiming to evaluate the overall clinical effectiveness and safety of a higher than conventionally used prophylactic dose of anticoagulation with tinzaparin administered for VTE prevention in non-critically ill COVID-19 patients with moderate disease severity. (3) Results: A total of 705 patients from 13 hospitals in Greece participated in the study (55% men, median age 62 years). Anticoagulation with tinzaparin was initiated immediately after admission. A full therapeutic dose was received by 36.3% of the participants (mean ± SD 166 ± 33 IU/Kgr/day) and the remaining patients (63.9%) received an intermediate dose (mean ± SD 114 ± 22 IU/Kgr/day). The median treatment duration was 13 days (Q1–Q3: 8–20 days). During the study (April 2020 to November 2021), 14 thrombotic events (2.0%) were diagnosed (i.e., three cases of pulmonary embolism (PE) and 11 cases of deep venous thrombosis, DVT). Four bleeding events were recorded (0.6%). In-hospital death occurred in 12 patients (1.7%). Thrombosis was associated with increasing age (median: 74.5 years, Q1–Q3: 62–79, for patients with thrombosis vs. 61.9 years, Q1–Q3: 49–72, p = 0.0149), increased D-dimer levels for all three evaluation time points (at admission: 2490, Q1–Q3: 1580–6480 vs. 700, Q1–Q3: 400–1475, p &lt; 0.0001), one week ± two days after admission (3510, Q1–Q3: 1458–9500 vs. 619, Q1–Q3: 352–1054.5, p &lt; 0.0001), as well as upon discharge (1618.5, Q1–Q3: 1010–2255 vs. 500, Q1–Q3: 294–918, p &lt; 0.0001). Clinical and laboratory improvement was affirmed by decreasing D-dimer and CRP levels, increasing platelet numbers and oxygen saturation measurements, and a drop in the World Health Organization (WHO) progression scale. (4) Conclusions: The findings of our study are in favor of prophylactic anticoagulation with an intermediate to full therapeutic dose of tinzaparin among non-critically ill patients hospitalized with COVID-19. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Intensive-Dose Tinzaparin in Hospitalized COVID-19 Patients: The INTERACT Study

(1) Background: It is well-established that coronavirus disease-2019 (COVID-19) is highly pro-inflammatory, leading to activation of the coagulation cascade. COVID-19-induced hypercoagulability is associated with adverse outcomes and mortality. Current guidelines recommend that hospitalized COVID-19 patients should receive pharmacological prophylaxis against venous thromboembolism (VTE). (2) INTERACT is a retrospective, phase IV, observational cohort study aiming to evaluate the overall clinical effectiveness and safety of a higher than conventionally used prophylactic dose of anticoagulation with tinzaparin administered for VTE prevention in non-critically ill COVID-19 patients with moderate disease severity. (3) Results: A total of 705 patients from 13 hospitals in Greece participated in the study (55% men, median age 62 years). Anticoagulation with tinzaparin was initiated immediately after admission. A full therapeutic dose was received by 36.3% of the participants (mean ± SD 166 ± 33 IU/Kgr/day) and the remaining patients (63.9%) received an intermediate dose (mean ± SD 114 ± 22 IU/Kgr/day). The median treatment duration was 13 days (Q1–Q3: 8–20 days). During the study (April 2020 to November 2021), 14 thrombotic events (2.0%) were diagnosed (i.e., three cases of pulmonary embolism (PE) and 11 cases of deep venous thrombosis, DVT). Four bleeding events were recorded (0.6%). In-hospital death occurred in 12 patients (1.7%). Thrombosis was associated with increasing age (median: 74.5 years, Q1–Q3: 62–79, for patients with thrombosis vs. 61.9 years, Q1–Q3: 49–72, p = 0.0149), increased D-dimer levels for all three evaluation time points (at admission: 2490, Q1–Q3: 1580–6480 vs. 700, Q1–Q3: 400–1475, p p p < 0.0001). Clinical and laboratory improvement was affirmed by decreasing D-dimer and CRP levels, increasing platelet numbers and oxygen saturation measurements, and a drop in the World Health Organization (WHO) progression scale. (4) Conclusions: The findings of our study are in favor of prophylactic anticoagulation with an intermediate to full therapeutic dose of tinzaparin among non-critically ill patients hospitalized with COVID-19