Strain Variability Research Articles

A Pair of Hearts: Two Cases of Mitral Valve Gonococcal Endocarditis.

Gonorrhea is a sexually transmitted infection. Manifestations include asymptomatic infection and disseminated, life-threatening disease. We present two cases of mitral valve gonococcal endocarditis and discuss epidemiologic trends in disseminated gonococcal infection, acknowledging antimicrobial resistance, genetic variability in gonococcal strains, and contextual factors related to the COVID-19 pandemic and STI control.

The Role of the Skin Microbiome in Acne: Challenges and Future Therapeutic Opportunities.

Acne vulgaris is a widespread dermatological condition that significantly affects the quality of life of adolescents and adults. Traditionally, acne pathogenesis has been linked to factors such as excess sebum production, follicular hyperkeratinization, and the presence of Cutibacterium acnes (C. acnes). However, recent studies have highlighted the role of the skin microbiome, shifting focus from individual pathogens to microbial community dynamics. This review critically evaluates existing research on the skin microbiome and its relationship to acne, focusing on microbial diversity, C. acnes strain variability, and emerging therapies targeting the microbiome. While certain studies associate C. acnes with acne severity, others show this bacterium's presence in healthy skin, suggesting that strain-specific differences and overall microbial balance play crucial roles. Emerging therapeutic approaches, such as probiotics and bacteriophage therapy, aim to restore microbial equilibrium or selectively target pathogenic strains without disturbing the broader microbiome. However, the lack of standardized methodologies, limited longitudinal studies, and the narrow focus on bacterial communities are major limitations in current research. Future research should explore the broader skin microbiome, including fungi and viruses, use consistent methodologies, and focus on longitudinal studies to better understand microbial fluctuations over time. Addressing these gaps will enable the development of more effective microbiome-based treatments for acne. In conclusion, while microbiome-targeted therapies hold promise, further investigation is needed to validate their efficacy and safety, paving the way for innovative, personalized acne management strategies.

Shining a light on Candida-induced epithelial damage with a luciferase reporter.

Host cell damage is a key parameter for research in infection biology, drug testing, and substance safety screening. In this study, we introduce a luciferase reporter system as a new and reliable assay to measure cell damage and validate it with the pathogenic yeast, Candida albicans, as a test case. We transduced human epithelial cell lines with a lentiviral vector to stably express an optimized luciferase enzyme, Nanoluc. Upon cell damage, the release of cytoplasmic luciferase into the extracellular space can be easily detected by a luminometer. We used the luciferase reporter system to investigate the damage caused by C. albicans to different newly generated epithelial reporter cell lines. We found that fungus-induced cell damage, as determined by established methods, correlated tightly with the release of the luciferase. The new luciferase reporter system is a simple, sensitive, robust, and inexpensive method for measuring host cell damage and has a sensitivity comparable to the standard assay, release of lactate dehydrogenase. It is suitable for high-throughput studies of pathogenesis mechanisms of any microbe, for antimicrobial drug screening, and many other applications.IMPORTANCEWe present a quick, easy, inexpensive, and reliable assay to measure damage to mammalian cells. To this end, we created reporter cell lines which artificially express luciferase, an enzyme that can be easily detected in the supernatant when these cells are damaged. We used infections with the well-investigated fungal pathogen of humans, Candida albicans, as a test case of our system. Using our reporter, we were able to recapitulate the known effects of strain variability, gene deletions, and antifungal treatments on host cell damage. This easily adaptable reporter system can be used to screen for damage in infection models with different microbial species, assay cell-damaging potential of substances, discover new non-toxic antibiotics, and many other damage-based applications.

Bridging the GAP: Probiotic Douches Redefining the Feminine Hygiene.

Vaginal douching is a centuries-old practice which is still in use, especially among adolescents. "Probiotic douches" are the vaginal douches that are formulated with probiotics and are intended to restore or maintain the vaginal microbiome balance. Probiotic douches are a new type of feminine hygiene product that claims to promote a balanced vaginal microbiome and improve overall well-being. However, the evidence supporting the use of probiotics for vaginal health is limited because of the variability in probiotic strains and dosages studied, and the lack of more comprehensive, long-term clinical trials. Most of the existing scientific literature on probiotics focuses on oral probiotic supplements and vaginal probiotic suppositories. Some potential benefits of probiotic douches include restoring a balanced vaginal microbiota, preventing, or managing infections, supporting local immune function, reducing odor and discharge, and enhancing overall vaginal comfort. However, it is important to note that these benefits have not been definitively proven and remain a subject of ongoing research. There are also potential risks associated with their use including disruption of the natural vaginal ecosystem by introducing foreign substances, risk of infection, and stability issues with the formulation that may lead to negative consequences. This review attempts to comprehend the critical need for robust scientific research to guide the safe and effective incorporation of probiotic douches into modern feminine hygiene practices, revolutionizing women's health, and well-being.

Pangenomes of human gut microbiota uncover links between genetic diversity and stress response

The genetic diversity of the gut microbiota has a central role in host health. Here, we created pangenomes for 728 human gut prokaryotic species, quadrupling the genes of strain-specific genomes. Each of these species has a core set of a thousand genes, differing even between closely related species, and an accessory set of genes unique to the different strains. Functional analysis shows high strain variability associates with sporulation, whereas low variability is linked with antibiotic resistance. We further map the antibiotic resistome across the human gut population and find 237 cases of extreme resistance even to last-resort antibiotics, with a predominance among Enterobacteriaceae. Lastly, the presence of specific genes in the microbiota relates to host age and sex. Our study underscores the genetic complexity of the human gut microbiota, emphasizing its significant implications for host health. The pangenomes and antibiotic resistance map constitute a valuable resource for further research.

Mycobacterium abscessus strain variability in preclinical drug development: does it really matter?

Abstract Background New treatment options for Mycobacterium abscessus infections are urgently needed. Since a correlation between MICs and clinical outcomes is not clearly established, potency of novel drugs needs to be evaluated using additional in vitro drug activity assays. Preclinical drug activity assays generally use the M. abscessus type strain ATCC 19977. However, M. abscessus complex entails a genetically and morphologically diverse group, and it is questionable whether drug activity observed against ATCC 19977 is representative of drug activity against clinical M. abscessus isolates. Objectives To assess whether the relationship between MIC and the quantitative antimycobacterial activity of amikacin, imipenem and clofazimine differs between the ATCC 19977 strain and clinical M. abscessus isolates. Methods Experiments were performed with M. abscessus ATCC 19977 and a subset of six clinical isolates covering the three M. abscessus subspecies and the smooth and rough morphotypes. Cultures were exposed to the drugs at 4-fold increasing, MIC-standardized concentrations, and the mycobacterial load was assessed over time. Results Concentration- and time-dependent activity of amikacin, imipenem and clofazimine against the six clinical isolates was similar. Only slight variations in drug activity were observed between ATCC 19977 and clinical isolates. Conclusions Time- and concentration-dependent drug activity against the ATCC 19977 strain seems indicative for in vitro drug behaviour against M. abscessus complex clinical isolates. Including one clinical smooth morphotype isolate alongside ATCC 19977 seems appropriate for reliable interpretation of this particular in vitro drug activity assay as part of the M. abscessus preclinical drug development pipeline.

Elucidating human gut microbiota interactions that robustly inhibit diverse Clostridioides difficile strains across different nutrient landscapes

The human gut pathogen Clostridioides difficile displays substantial inter-strain genetic variability and confronts a changeable nutrient landscape in the gut. We examined how human gut microbiota inter-species interactions influence the growth and toxin production of various C. difficile strains across different nutrient environments. Negative interactions influencing C. difficile growth are prevalent in an environment containing a single highly accessible resource and sparse in an environment containing C. difficile-preferred carbohydrates. C. difficile toxin production displays significant community-context dependent variation and does not trend with growth-mediated inter-species interactions. C. difficile strains exhibit differences in interactions with Clostridium scindens and the ability to compete for proline. Further, C. difficile shows substantial differences in transcriptional profiles in co-culture with C. scindens or Clostridium hiranonis. C. difficile exhibits massive alterations in metabolism and other cellular processes in co-culture with C. hiranonis, reflecting their similar metabolic niches. C. hiranonis uniquely inhibits the growth and toxin production of diverse C. difficile strains across different nutrient environments and robustly ameliorates disease severity in mice. In sum, understanding the impact of C. difficile strain variability and nutrient environments on inter-species interactions could help improve the effectiveness of anti-C. difficile strategies.

Determination of strain variability and kinetics of food-associated microorganisms following ultrasound treatment

Ultrasound is a promising emerging technology known for its antimicrobial efficacy. However, existing studies have not fully addressed the impact of strain variability and inactivation kinetics on US efficacy. Ten strains of Listeria monocytogenes, Lactiplantibacillus plantarum, Saccharomyces cerevisiae and Escherichia coli were exposed to US treatment (26 kHz, 200 mL, 100 % amplitude, 200 W, 65–71 W/cm2) under dynamic conditions to investigate their resistance profile. Furthermore, the inactivation kinetics of selected resistant/sensitive strains were assessed. The result showed significant intra-species variability in resistance (p < 0.05) for the four target microorganisms evaluated in this study. L6 and NCTC 10357 were the most resistant and sensitive L. monocytogenes strains respectively, having a reduction difference of ∼3.4 log CFU/mL. Regarding L. plantarum, FBR04 emerged as the most resistant strain (4.4 log reduction), while E. coli FAM21845, FAM21805 and FAM21843 (∼2 log reduction) emerged as the most resistant strains. On the other hand, the most resistant strains of S. cerevisiae were CBS 1544, AD 1890 and 077.0001 (<1 log reduction) while S. cerevisiae AD 2913, 028.0404 and 028.0315 were the most sensitive (>5 log reduction). The survival curves of most of the strains exhibited an initial phase of insignificant microbial inactivation followed by a relatively fast log-linear inactivation period. The estimated D-value showed that L. monocytogenes strains exhibited higher resistance to US treatment than any other species, while other species displayed comparable resistance. The findings on strain variability resistance and inactivation kinetics following US treatment are essential for food safety and will pave the way for further research on microbial response to US stress, risk assessment and optimisation studies.

Clinical utility of ambulatory ECG monitoring and 2D-ventricular strain for evaluation of post-COVID-19 ventricular arrhythmia

BackgroundA relatively common complication of COVID -19 infection is arrhythmia. There is limited information about myocardial deformation and heart rate variability (HRV) in symptomatic post COVID patients presented by ventricular arrhythmia.Aim of the studyOur goal was to assess 2D-ventricular strain and heart rate variability indices (evaluated by ambulatory ECG monitoring) in post-COVID-19 patients suffering from ventricular arrhythmia.MethodsThe current observational case–control study performed on 60 patients one month after they had recovered from the COVID-19 infection. Thirty healthy volunteers served as the control group. Each participant had a full medical history review, blood tests, a 12-lead surface electrocardiogram (ECG), 24-h ambulatory ECG monitoring, and an echo-Doppler examination to evaluate the left ventricular (LV) dimensions, tissue Doppler velocities, and 2D-speckle tracking echocardiography (2D-STE) for both the LV and right ventricular (RV) strain.ResultsSymptomatic post-COVID patients with monomorphic premature ventricular contractions (PVCs) showed a substantial impairment of LV/RV systolic and diastolic functions, LV/RV myocardial performance (MPI) with reduced indices of HRV. Patients with higher versus lower ventricular burden had poorer functional status, higher levels of inflammatory biomarkers and reduced parameters of HRV (New York Heart Association (NYHA) class: 2.1 ± 0.9 vs. 1.5 ± 0.6, p < 0.001, C-reactive protein (CRP): 13.3 ± 4.1 vs. 8.3 ± 5.9 mg/L, p < 0.0001, low frequency/high frequency (LF/HF): 3.6 ± 2.4 vs. 2.2 ± 1.2, p < 0.002, the root mean square of the difference between successive normal intervals (rMSSD): 21.8 ± 4.7 vs. 29.3 ± 14.9 ms, p < 0.039 and the standard deviation of the RR interval (SDNN): 69.8 ± 19.1 vs.108.8 ± 37.4 ms, p < 0.0001). The ventricular burden positively correlated with neutrophil/lymphocyte ratio (NLR) (r = 0.33, p < 0.001), CRP (r = 0.60, p < 0.0001), while it negatively correlated with LV-global longitudinal strain (GLS) (r = -0.38, p < 0.0001), and RV-GLS (r = -0.37, p < 0.0001).ConclusionsPatients with post-COVID symptoms presented by ventricular arrhythmia had poor functional status. Patients with post-COVID symptoms and ventricular arrhythmia had subclinical myocardial damage, evidenced by speckle tracking echocardiography while having apparently preserved LV systolic function. The burden of ventricular arrhythmia in post-COVID patients significantly correlated with increased inflammatory biomarkers and reduced biventricular strain.

Survival of Twelve Pathogenic and Generic Escherichia coli Strains in Agricultural Soils as Influenced by Strain, Soil Type, Irrigation Regimen, and Soil Amendment

Biological soil amendments of animal origin (BSAAO) play an important role in agriculture but can introduce pathogens into soils. Pathogen survival in soil is widely studied, but data are needed on the impacts of strain variability and field management practices. This study monitored the population of 12 Escherichia coli strains (generic, O157, and non-O157) in soils while evaluating the interactions of soil type, irrigation regimen, and soil amendment in three independent, greenhouse-based, randomized complete block design trials. Each E. coli strain (4–5 log10 CFU/g) was homogenized in bovine manure amended or nonamended sandy-loam or clay-loam soil. E. coli was enumerated in 25 g samples on 0, 0.167 (4 h), 1, 2, 4, 7, 10, 14, 21, 28, 56, 84, 112, 168, 210, 252, and 336 days postinoculation (dpi). Regression analyses were developed to understand the impact of strain, soil type, irrigation regimen, and soil amendment on inactivation rates. E. coli survived for 112 to 336 dpi depending on the treatment combination. Pathogenic and generic E. coli survived 46 days [95% Confidence interval (CI) = 20.85, 64.72; p = 0.001] longer in soils irrigated weekly compared to daily and 146 days (CI = 114.50, 184.50; p < 0.001) longer in amended soils compared to unamended soils. Pathogenic E. coli strains were nondetectable 69 days (CI = 39.58, 98.66, p = 0.015) earlier than generic E. coli strains. E. coli inactivation rates demonstrated a tri-phasic pattern, with breakpoints at 26 dpi (CI = 22.3, 29.2) and 130 dpi (CI = 121.0, 138.1). The study findings demonstrate that using bovine manure as BSAAO in soil enhances E. coli survival, regardless of strain, and adequate food safety practices are needed to reduce the risk of crop contamination. The findings of this study contribute data on E. coli concentrations in amended soils to assist stakeholders and regulators in making risk-based decisions on time intervals between the application of BSAAO and the production and harvest of fruits and vegetables.

The maturation of native uropathogenic Escherichia coli biofilms seen through a non-interventional lens

Urinary tract infections (UTI) caused by uropathogenic Escherichia coli (UPEC) are a significant global health challenge. The UPEC biofilm lifestyle is believed to play an important role in infection recurrency and treatment resistance, but our understanding of how the extracellular matrix (ECM) components curli and cellulose contribute to biofilm formation and pathogenicity is limited. Here, we study the spatial and temporal development of native UPEC biofilm using agar-based detection methods where the non-toxic, optically active fluorescent tracer EbbaBiolight 680 reports the expression and structural location of curli in real-time. An in vitro screen of the biofilm capacity of common UPEC strains reveals significant strain variability and identifies UPEC No. 12 (UPEC12) as a strong biofilm former at 28 °C and 37 °C. Non-interventional microscopy, including time-lapse and 2-photon, reveal significant horizontal and vertical heterogeneity in the UPEC12 biofilm structure. We identify region-specific expression of curli, with a shift in localization from the bottom of the flat central regions of the biofilm to the upper surface in the topographically dramatic intermediate region. When investigating if the rdar morphotype affects wettability of the biofilm surface, we found that the nano-architecture of curli guided by cellulose, rather than the rdar macrostructures, leads to increased hydrophobicity of the biofilm. By providing new insights at exceptional temporal and spatial resolution, we demonstrate how non-interventional analysis of native biofilms will facilitate the next generation of understanding into the roles of ECM components during growth of UPEC biofilms and their contribution to the pathogenesis of UTI.

Compressive stress–strain relationship and its variability of basalt fiber reinforced recycled aggregate concrete

Basalt fiber reinforced recycled aggregate concrete (BFRAC) is a high-performance, environmentally friendly material that combines lightweight, high-strength fibers with low-carbon recycled aggregates (RAs), positioned for extensive use in building structures. However, research on its constitutive relationships is currently scarce, which partly restricts component design and analysis. In this context, the current study thoroughly explores the stress–strain relationship and variability of BFRAC under compression, using 240 cylinders for testing to investigate the influence of factors like coarse/fine RA sources, RA replacement rates, and fiber dosage. The study found that the addition of RAs and fibers reduced the workability of the mixture, particularly with the inclusion of fine RAs and short-cut fibers. Using coarse and fine RAs generally reduces the material’s elastic modulus, compressive strength, and post-peak ductility. Adding fibers can slightly improve compressive strength and peak strain, significantly reduce material brittleness, and have a minimal impact on elastic modulus. Importantly, the study noted that the pre-peak segment of the stress–strain curve of BFRAC is most sensitive to the addition of fine RAs, while the post-peak segment is most sensitive to fiber content. Despite this, using high-quality RAs up to 50% replacement and adding 0.4% by volume of fiber can make BFRAC with mechanical properties comparable to natural aggregate concrete. Based on the observed tests, this paper proposes constitutive relationships that incorporate skeleton curves and variability at different points for the compressive stress–strain behavior of BFRAC.

Disinfectant efficacy of glabridin against dried and biofilm cells of Listeria monocytogenes and the impact of residual organic matter

Glabridin is an antimicrobial compound which can be extracted from plants, such as liquorice (Glycyrrhiza glabra) roots. Although its activity against foodborne pathogens and spoilage microorganisms has already been reported, the investigation of potential applications as a surface disinfectant is still largely unexplored. Hence, this study evaluated the disinfectant efficacy of glabridin against Listeria monocytogenes. The activity of glabridin was first tested in vitro in a nutrient-rich medium against eight strains of L. monocytogenes, including food isolates and the model strain EGDe. The tested strains showed similar susceptibility with minimal inhibitory and bactericidal concentrations of 12.5 µg/mL and 25 µg/mL, respectively. Subsequently, L. monocytogenes L6, FBR17 and EGDe were selected to assess the efficacy of glabridin against dried cells (according to the European standard EN 13697:2015 + A1:2019) and biofilm cells on stainless steel surfaces. Moreover, the impact of food residual organic matter was investigated using skim milk, cantaloupe and smoked salmon solution as soiling components. Our results showed that applying 200 µg/mL of glabridin resulted in a substantial reduction (>3 log10) of dried and biofilm cells of L. monocytogenes in standard conditions (i.e. low level of residual organic matter). Cantaloupe soiling components slightly reduced the activity of glabridin, while the efficacy of glabridin when tested with salmon and skim milk residuals was substantially affected. Comparative analysis using standardized protein contents provided evidence that the type of food matrices and type of proteins may impact the activity of glabridin as a disinfectant. Overall, this study showed low strain variability for the activity of glabridin against L. monocytogenes and shed light on the possible application of this natural antimicrobial compound as a surface disinfectant.

Evaluation of strain variability of food microorganisms in response to decontamination by pulsed electric fields and thermal treatments

The effect of pulsed electric fields (PEF) and thermal treatments on the inactivation of the population of 40 strains of 4 model microorganisms (Escherichia coli, Listeria monocytogenes, Lactiplantibacillus plantarum, Saccharomyces cerevisiae) were investigated. Microbial samples of McIlvaine buffer pH 7.0 were subjected to pulses with electric field strength 20 kV/cm and total specific energies (88, 136, and 184 kJ/kg). Depending on the species and strain, microorganisms exhibited various resistances. PEF microbial resistance and strain variability data were correlated to the total specific energy used. E. coli strains showed statistical log10 inactivation differences under the 88 and 136 kJ/kg but not under the 184 kJ/kg PEF treatment. In contrast, L. monocytogenes strains showed statistical log10 inactivation differences only under the 184 kJ/kg treatment. L. monocytogenes L6 strain was identified as the most resistant strain at PEF treatment (184 kJ/kg). This result was in accordance with the resistance under thermal treatment (62.8 °C, 30 min). Industrial relevanceThe identification of target microorganisms related to their resistance in one or more technologies can help at establishing treatment conditions that reassure food safety. Data obtained in this research show that species and strain behaviours vary and are dependent on the technology and the applied treatment conditions. Thus, the resistance exhibited by microorganisms of public health importance may be dependent on the used technology and the applied treatment.

The In Vitro Antibacterial Activity of Phytogenic and Acid-Based Eubiotics against Major Foodborne Zoonotic Poultry Pathogens.

The aim of the study was to investigate in vitro the antibacterial activity of 8 commercial drinking water additives against major zoonotic poultry pathogens (Campylobacter spp., Escherichia coli, Salmonella Typhimurium, Staphylococcus aureus and Listeria spp.). We tested two essential oil-based phytogenics (Phyto CSC Liquide B, AEN 350 B Liquid), two acid-based eubiotics (Salgard® liquid, Intesti-Flora), and four blends of essential oils and organic acids (ProPhorceTM SA Exclusive, Herbal acid, Rigosol-N and Eubisan 3000). The antibacterial activity was determined by estimating the minimum inhibitory concentration (MIC) using a microdilution method. The MICs of the products against Campylobacter spp. ranged from 0.071% to 0.568% v/v, in which Herbal acid, a blend rich in lactic and phosphoric acids, also containing thyme and oregano oils, exhibited the highest efficacy (MIC: 0.071% v/v) against all the tested strains. The MICs of the tested products against Escherichia coli ranged between 0.071% and 1.894% v/v. Specifically, the MIC of Rigosol-N, a blend of high concentrations of lactic and acetic acid, was 0.142% v/v for both tested strains, whereas the MICs of Intesti-Flora, a mixture rich in lactic and propionic acid, ranged from 0.284% to 0.568% v/v. The MICs of the products against Salmonella Typhimurium were between 0.095% and 1.894% v/v. Specifically, the MIC of Eubisan 3000, a blend rich in oregano oil, was 0.284% v/v. The MICs against Staphylococcus aureus were between 0.142% and 9.090% v/v. The MICs of Phyto CSC Liquide B, which is rich in trans-cinnamaldehyde, were between 3.030% and 9.090% v/v, showing the highest MIC values of all tested products. Finally, the MIC values of the tested commercial products against Listeria spp. were 0.095% to 3.030% v/v. The MICs of ProPhorceTM SA Exclusive, a highly concentrated blend of formic acid and its salts, were 0.095-0.142% v/v against Listeria spp., while the MICs of AEN 350 B Liquid were between 0.284% and 1.894% exhibiting high Listeria spp. strain variability. In conclusion, all the selected commercial products exhibited more or less antibacterial activity against pathogenic bacteria and, thus, can be promising alternatives to antibiotics for the control of zoonotic poultry pathogens and the restriction of antimicrobial-resistant bacteria.

Tensile analysis of loop joints with different overlap lengths

ABSTRACT In order to achieve rapid bridge construction, on-site wet joint joining techniques for prefabricated bridge decks are commonly used. The primary method involves mainly lap welding, but this form poses some drawbacks such as difficult lap jointing of two steel bars and a hefty welding workload. To address these issues, this study conducts model experiments on the unwelded structure of loop joints. We compare and analyze the displacement, crack distribution, crack development process, and strain variability of loop joints across three different overlap lengths, along with one type of straight bar lap-welded wet joints. It is observed that, despite the comparable ultimate tensile capacity of loop joints with the main rib to that of the welded wet joint with the main rib, the failure mode varies, and the crack direction changes with the overlap length. From a structural stress perspective, if the U-bar of the loop joint meets a specific overlap length, the wet joint adequately fulfills stress requirements and can be applied in practical engineering.

Disentangling the effects of electroporation and heat during pulsed electric field (PEF) processing of oat-based milk alternative: A case study on Lactiplantibacillus plantarum inactivation

The study aimed to quantify the resistance of two L. plantarum strains and estimate the contribution of temperature during the pulsed electric field (PEF) processing of oat beverage. PEF and thermal inactivation kinetic experiments of L.plantarum strains were performed separately. Log10 reductions ≥5.7 of L. plantarum was achieved when 10–24 kV/cm, 110–115 kJ/L, 80–522 μs, and 35 °C inlet temperature were applied, while strain variability was evident in the performed assessments. Accurate monitoring of the temperature profiles for PEF allowed the estimation of the thermal microbial inactivation which was separated from electroporation effect. The electroporation impact was found to increase with increasing electric field strengths. Temperature measurements in the treatment zone confirmed the presence of hot spots. At higher specific energy inputs, there was significant contribution of temperature to the total observed inactivation. This contribution became smaller when the flow rate was increased, as shorter residence time reduced the exposure to high temperature peaks. Industrial relevanceThe findings demonstrated the potential of PEF as a promising technology for the microbial decontamination of oat-based milk alternative. Knowledge of strain variability in response to emerging food processing technologies is critical during process optimisation and quantitative microbial risk assessment. New developments in PEF equipment and process should ideally aim to maximize inactivation while minimizing the impact of high temperature on sensitive food constituents.

The Tomato Variety Affects the Survival of Shigella flexneri 2a in Fruit Pericarp.

The presence of enteric pathogens in produce can serve as a significant means of transmitting infections to consumers. Notably, tomatoes, as a type of produce, have been implicated in outbreaks caused by various human pathogens, such as Salmonella enterica and pathogenic Escherichia coli. However, the survival characteristics of Shigella spp. in tomatoes have not been thoroughly investigated. In this study, we assess the survival of S. flexneri 2a in two distinct varieties of post-harvested tomatoes. S. flexneri 2a was used to inoculate both regular-sized Vine tomatoes and cherry-type Mini Plum tomatoes. Our findings reveal no significant difference in Shigella survival in the pericarp of both varieties on day 2 post-inoculation. However, a significant disparity emerges on day 6, where all recovered Shigella colonies exclusively belong to the Mini Plum variety, with none associated with the Vine type. When Shigella was inoculated into the locular cavity (deep inoculation), no significant difference between varieties was observed. Additionally, we investigate the potential role of the SRL pathogenicity island (SRL PAI) in the survival and fitness of S. flexneri 2a in post-harvested tomatoes. Our results indicate that while the SRL PAI is not linked to the survival of the strains in tomato, it does impact their fitness. These findings underscore the variability in Shigella strains' survival capabilities depending on the tomato variety, highlighting the importance of understanding Shigella ecology beyond the human host and identifying molecular determinants influencing bacterial survival to mitigate the risk of future outbreaks. The significance of this data on Shigella persistence in fresh vegetables should not be underestimated, as even a small number of Shigella cells can pose a threat to the health of individuals.

Influence of spatial variability of soil shear-wave velocity considering intralayer correlation on seismic response of engineering site

Shear-wave velocity uncertainty significantly impacts seismic response analysis at engineering sites. Previous studies focused on the correlations of shear-wave velocities within soil layers. However, the influence of the vertical spatial variability of shear-wave velocity within individual soil layers was not considered. This study selected a typical Site Class II engineering site to investigate this influence based on the equivalent linear seismic response analysis method of layered soil deposits. Existing field test data on shear-wave velocity were used to discretize the shear-wave velocity within soil layers into a one-dimensional (1D) random field through covariance matrix decomposition and local average process theory. Monte Carlo simulations generated random shear-wave velocity profiles with different vertical correlation distances. Three artificial records with different earthquake return periods were used as input motions at the engineering bedrock for the 1D free-field model. Considering soil shear-wave velocity uncertainty, the peak shear strain increased by 19–27% with the input ground motion amplitude. Moreover, the site peak shear strain variability increased by 25–34% with the vertical correlation distance. The proposed 1D random field model effectively simulated the interlayer correlation and spatial variability of shear-wave velocity within soil layers, demonstrating its significance in seismic response analysis.

Impact of species and strain variability on non-thermal plasma decontamination efficacy

Microwave non-thermal plasma (NTP) is a promising preservation technology for surface decontamination, alternative to conventional methods such as heat treatments and chemical additives. This study explores the impact of plasma processed air (PPA) exposure on 50 strains from five diverse microbial species relevant to food quality and safety. Bacterial vegetative cells were effectively inactivated in an agar plate model system. The average reduction after 60 s of treatment was 4.9 log10, 5.8 log10, and 5.9 log10 for Listeria monocytogenes, Escherichia coli, and Lactiplantibacillus plantarum respectively, with limited strain variability. Saccharomyces cerevisiae reached an average of 5.3 log10 reduction after 30 s of treatment, with one resistant strain (AD1890). Bacillus subtilis spores were inactivated by 2.0 log10 on average after 30 min, with two distinct strain groups. These results showed that PPA can be used as a mild decontamination treatment applicable to dry and heat-sensitive surfaces, suitable for various food applications.