Log Reduction Research Articles

Measuring the performance of conventional and emerging ultraviolet-C light sources for bacterial, fungal, and mycotoxin control

The performance of two conventional monochromatic ultraviolet-C (UV-C) low pressure mercury (LPM) sources (single and multiple lamps) was measured and compared with three emerging UV sources: a monochromatic KrCl* excimer lamp and UV-LEDs, and a polychromatic pulsed light (UV-C PL) lamp. Fluence-based kinetic parameters and electrical energy per order (EE0) of the UV sources was determined for the inactivation of E. coli bacteria, the reduction of deoxynivalenol (DON) mycotoxin, and F. graminearum spore growth to assess feasibility for various processing targets. The impact on E. coli photoreactivation and dark repair was also assessed. Each of the five UV sources excelled in certain applications while not being feasible for others. The UV-C PL lamp was the most effective for E. coli inactivation, requiring the lowest fluence of 1.4 mJ/cm2 for 5-log10 reduction. The KrCl* excimer lamp was the most effective for preventing subsequent photoreactivation. The UV-LEDs and LPM lamp were equally effective for reducing fungal spore growth requiring 77.0 and 90.1 mJ/cm2 to achieve 90% reduction, respectively. The KrCl* excimer and UV-C PL lamps were the most effective at reducing DON contamination requiring 1250 and 500 mJ/cm2 to achieve 90% reduction, respectively. The evaluation of EE0 showed that the conventional LPM source with multiple lamps had approximately 2–3-fold better electrical efficiency for the reduction of all three tested targets due to its high wall plug efficiency compared to the next best UV-C PL lamp. This indicates that energy efficiency of emerging UV sources needs to be improved in further development.

BAP: Bilateral asymptotic pruning for optimizing CNNs on image tasks

Pruning facilitates the acquisition of efficient convolutional neural networks (CNNs) tailored for resource-limited environments. General pruning strategies for CNNs are typically based on the characteristics of filters or their generated feature maps. These strategies assume that the similarity between these elements remains highly consistent. Nevertheless, our analysis has shown that this assumption does not always hold, potentially causing pruning methods to misjudge parameter redundancy. It may erroneously remove crucial network parameters, leading to severe performance loss after network compression. This paper proposes a novel method termed Bilateral Asymptotic Pruning (BAP) for channel optimization. BAP conducts density-based clustering on filters and corresponding feature maps separately to identify redundancy. The resulting sets of channel numbers are then fused for bilateral collaborative pruning. Additionally, we present an exponential moving average method with a logarithmic reduction to mitigate the effects of pruning errors on performance. Finally, the compressing rate of networks gradually increases during the asymptotic process, thereby allowing for the precise generation of pruned networks of different sizes in a single experiment. Extensive experiments demonstrate that our BAP outperforms many state-of-the-art methods. For instance, BAP reduces 51.56% parameters and 59.90% FLOPs1 of ResNet-50 with only 0.5% TOP-5 accuracy loss on ImageNet.

Effectiveness of laser pulsed irradiation for antimicrobial photodynamic therapy

The aim of this study was to compare two types of light irradiation devices for antimicrobial photodynamic therapy (aPDT). A 660-nm light-emitting diode (LED) and a 665-nm laser diode (LD) were used for light irradiation, and 0.1 mg/L TONS 504, a cationic chlorin derivative, was used as the photosensitizer. We evaluated the light attenuation along the vertical and horizontal directions, temperature rise following light irradiation, and aPDT efficacy against Staphylococcus aureus under different conditions: TONS 504 only, light irradiation only, and TONS 504 with either LED (30 J/cm2) or LD light irradiation (continuous: 30 J/cm2; pulsed: 20 J/cm2 at 2/3 duty cycle, 10 J/cm2 at 1/3 duty cycle). Both LED and LD light intensities were inversely proportional to the square of the vertical distance from the irradiated area. Along the horizontal distance from the nadir of the light source, the LED light intensity attenuated according to the cosine quadrature law, while the LD light intensity did not attenuate within the measurable range. Following light irradiation, the temperature rise increased as the TONS 504 concentration increased in the order of pulsed LD < continuous LD < LED irradiation. aPDT with light irradiation only or TONS 504 only had no antimicrobial effect, while aPDT with TONS 504 under continuous or pulsed LD light irradiation provided approximately 3 log reduction at 30 J/cm2 and 20 J/cm2 and approximately 2 log reduction at 10 J/cm2. TONS 504-aPDT under pulsed LD light irradiation provided anti-microbial effect without significant temperature rise.

Performance evaluation of integrating Vertical Garden Constructed Wetlands (VGCWs) with diverse plant species and modified media for treating septic tank effluent

Vertical Garden Constructed Wetland (VGCW) system has been used as a secondary treatment system to improve effluent quality of septic tanks and cesspools by enhancing nutrients, organic and solid removal according to the guidelines of effluent discharge. This study aimed to investigate the treatment performance of the VGCWs by integrating with diverse plant species and modified media used as secondary treatment for conventional or solar septic tanks. In the study, laboratory-scale VGCW utilizing soil as the media and planted with Water Pennywort were operated at hydraulic retention times (HRT) of 6, 12, and 24 h, while modified planted vertical garden constructed wetlands (mpVGCW) operated at an HRT of 36 h, was fed with effluent collected from a septic tank. The treatment performance of VGCWs treating effluent from the septic tank and operating at an HRT of 24 h was found to achieve the highest removal efficiencies for organic matter, nutrients, and solids (up to over 90%), compared to an HRT of 6 or 12 h. Moreover, the highest log reduction of E.coli of 2.8 was also observed at the 24 h HRT, in comparison to HRTs of 6 or 12 h. The Spider Ivy, Coleus, and Selaginella frosty could be planted in the mpVGCW system to enhance the overall treatment efficiencies with consistently showed high removal efficiencies for TCOD (91.37–93.39%), TKN (97.1–97.8%), and TP (87.18–88.58%). These results suggested the potential of the VGCWs as a secondary treatment system for polishing septic tank effluent and improving environmental quality.

Effectiveness of ceiling-mounted ultraviolet-C lamps: An experimental study in a biocontainment unit of a tertiary care hospital

We aimed to evaluate the performance of ceiling-mounted UV-C lamps. This study was conducted in an empty room with UV-C lamps in the biocontainment unit of a tertiary care hospital in South Korea. Each pathogen (Staphylococcus aureus, Escherichia coli, Candida krusei, Bacillus cereus, and Mycobacterium peregrinum) was inoculated on blood agar plates and placed in 20 selected places from the UV-C lamp, and irradiation was applied for 15 min. As a control group, the bacterial solution was diluted 10,000 times and UV was not applied. A mean ± SD of 5.95 ± 0.91 log reduction was observed with UV irradiation compared with the control. The log reduction was greatest for S. aureus [median, 7.05 (IQR, 6.49-7.26)] and least for M. peregrinum [median, 4.88 (IQR, 4.58-5.24)]. The degree of log reduction was inversely proportional to the square of the distance from the UV-C lamp (R2 = -0.12, P<.001). In this study, ceiling-mounted UV-C demonstrated effective disinfection of at least 4-log reduction of the test organisms within a 4-m distance. Mounted UV-C lighting is a considerable option for improving surface disinfection.

Visible light-responsive polylactic acid@pullulan-chitosan/homojunction g-C3N4 bilayer antimicrobial films for fruit preservation

The development of novel packaging materials with antimicrobial properties is crucial in preventing the microbial-induced spoilage of fruits, vegetables, and foodborne illnesses. In this study, homojunction g-C3N4 (HCN) photocatalysts with excellent photocatalytic performance were incorporated into a matrix consisting of pullulan/chitosan (Pul/CS). These photocatalysts were then electrostatically spun onto polylactic acid (PLA) films to fabricate PLA@Pul/CS/HCN nanofibrous composite films. The design of the bilayer films aimed to combine the physical properties of PLA film with the excellent antibacterial properties of nanofiber films, thereby achieving synergistic advantages. The incorporation of the HCN photocatalysts resulted in enhanced hydrophobicity, barrier function, and mechanical properties of the composite films. Under visible light irradiation, the PLA@Pul/CS/HCN films exhibited approximately 3.43 log and 3.11 log reductions of Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA), respectively, within 2 h. The excellent antimicrobial performance could be attributed to the synergistic effect of CS and the release of reactive oxygen species (ROS) from HCN. Moreover, the strawberries packaged in the PLA@Pul/CS/HCN film demonstrated diminished quality degradation and a prolonged shelf life following visible light irradiation treatment. This study will provide new insights into the exploration of safe and efficient antimicrobial food packaging.

Biomaterial-based sponge for efficient and environmentally sound removal of bacteria from water

Designing materials capable of disinfecting water without releasing harmful by-products is an ongoing challenge. Here, we report a novel polycationic sponge material synthesized from chitosan derivatives and cellulose fibers, exhibiting antibacterial properties. The design of such material is based on three key principles. First, the formation of a highly porous structure through cryogelation for an extensive surface area. Second, the incorporation of cationic quaternary ammonium moieties onto chitosan to enhance bacterial adsorption and antibacterial activity. Lastly, the reinforcement of mechanical properties through integration of cellulose fibers. The presented sponge materials exhibit up to a 4-log (99.99%) reduction within 6 h against both gram-positive B. subtilis and gram-negative E. coli. Notably, QCHI90/Cell, with the highest surface charge, exhibits a 2–4.5 log reduction within 1 h of incubation time. The eco-friendly synthesis from water and readily available biomaterials, along with cost-effectiveness and simplicity, underscores its versatility and feasibility of upscaling. Together with its outstanding antibacterial activity, this macroporous biomaterial emerges as a promising candidate for water disinfection applications.

Enhancing microbial safety and quality of milk with ultrasonication: Kinetics modeling of pathogenic Bacteria and milk characteristics

This study investigated the non-thermal inactivation kinetics of S. aureus NCDC109, E. coli EMC17, and Salmonella Typhimurium SMC25 in milk through ultrasonication, while concurrently evaluating its impact on milk's physicochemical properties. Milk samples post-inoculation, underwent treatment with varying ultrasonic amplitudes (40–70%) over different time intervals (0–30 min). The highest logarithmic reduction of 6.12, 6.19, and 5.68 for S. aureus NCDC109, E. coli EMC17, and S. Typhimurium SMC25, respectively, was attained with 70% amplitude for 30 min. Weibull model exhibited superior fit with lower sum of squared errors (SSE), mean square error (MSE), root mean square error (RMSE), Akaike information criterion (AIC) values as compared to the linear model. The Weibull model accurately predicted D-values for all strains and treatments, with proper accuracy factor (Af) and bias factor (Bf)values. The 5-log reduction time for E. coli EMC17 decreased from 46.05 to 20.01 min with amplitude increasing from 40% to 70%. Ultrasonication preserved milk's physicochemical properties, encompassing particle size, zeta potential, color, pH and viscosity. This study highlights the potential of ultrasonication in the dairy sector to combat bacterial contamination in milk and provides a valuable tool for predicting and validating responses using kinetic models for pathogens in milk.

The potential of pulsed electromagnetic field-generated shock waves for reducing microbial load and improving homogenization in raw milk

Milk is a highly nutritious food essential for human consumption. However, traditional thermal processing methods can reduce its nutritional value and cause unwanted changes. The use of shock waves produced by pulsed electromagnetic fields (PEMFs) has been explored as a means to reduce pathogenic microorganisms. The effect of shock wave treatment on microbial load and particle distribution in packaged fresh cow's milk was investigated. Additionally, the impact of shock wave treatment on Salmonella enterica counts in a bacterial suspension of phosphate-buffered saline (PBS) was evaluated, as this bacterium is a significant milkborne pathogen. Treatment with 1000 impulses from an electromagnetic shock wave generator resulted in a 0.7-log reduction in the total bacterial count of milk. In a separate experiment, a 300-impulse shock wave treatment applied to a Salmonella enterica suspension achieved a 3-log reduction in bacterial counts. Furthermore, shock wave treatment resulted in a decrease in milk particle size compared to untreated milk. Notably, the volume of milk used in this study aligns with commercially available packaged products, enhancing the experiment's industrial relevance. The use of PEMF to generate shock waves could provide a novel approach for future studies focused on reducing the microbial load of milk and improving its homogenization.

Studying the viability and growth kinetics of vancomycin-resistant Enterococcus faecalis V583 following femtosecond laser irradiation (420–465 nm)

Enterococcus faecalis is among the most resistant bacteria found in infected root canals. The demand for cutting-edge disinfection methods has rekindled research on photoinactivation with visible light. This study investigated the bactericidal activity of femtosecond laser irradiation against vancomycin-resistant Enterococcus faecalis V583 (VRE). The effect of parameters such as wavelength and energy density on the viability and growth kinetics of VRE was studied to design an optimized laser-based antimicrobial photoinactivation approach without any prior addition of exogenous photosensitizers. The most effective wavelengths were 430 nm and 435 nm at a fluence of 1000 J/cm2, causing a nearly 2-log reduction (98.6% and 98.3% inhibition, respectively) in viable bacterial counts. The colony-forming units and growth rate of the laser-treated cultures were progressively decreased as energy density or light dose increased at 445 nm but reached a limit at 1250 J/cm2. At a higher fluence of 2000 J/cm2, the efficacy was reduced due to a photobleaching phenomenon. Our results highlight the importance of optimizing laser exposure parameters, such as wavelength and fluence, in bacterial photoinactivation experiments. To our knowledge, this is the first study to report an optimized wavelength for the inactivation of VRE using visible femtosecond laser light.

Characterization of two novel Salmonella phages having biocontrol potential against Salmonella spp. in gastrointestinal conditions

Salmonella is a primary enteric pathogen related to the contamination of poultry and other food products in numerous foodborne outbreaks. The continuous emergence of multidrug-resistant bacteria has become a serious issue due to the overuse of antibiotics. Hence, lytic phages are considered alternative biocontrol agents against these bacterial superbugs. Here, two Salmonella phages—S4lw and D5lw—were subjected to genomic and biological characterization and further encapsulated to improve the stability under acidic conditions mimicking gastrointestinal conditions. The two lytic phages, S4lw and D5lw, taxonomically belong to new species under the Guernseyvirinae and Ackermannviridae families, respectively. Each phage showed antimicrobial activities against diverse Salmonella spp., such as S. Enteritidis and S. Typhimurium, achieving 1.7–3.4 log reduction after 2–6 h of treatment. The phage cocktail at a multiplicity of infection (MOI) of 100 or 1000 completely inhibited these Salmonella strains for at least 14 h at 25 °C. Additionally, the bead-encapsulated phage cocktail could withstand low pH and different simulated gut environments for at least 1 h. Overall, the newly isolated phages can potentially mitigate Salmonella spp. under the gastrointestinal environments through encapsulation and may be further applied via oral administration to resolve common antimicrobial resistance issues in the poultry production chain.

Morphological aspects and the effectiveness of photodynamic inactivation against Rhizopus oryzae in different life cycles.

Mucormycosis is an extremely aggressive fungal disease with a high mortality rate, especially in people with compromised immune systems. Most cases of mucormycosis are caused by the fungus Rhizopus oryzae. The treatments used are based on high doses of antifungals, associated with surgical resections, when it is possible. However, even with this aggressive treatment, the estimated attributable mortality rate is high. There is therefore a need to develop adjuvant treatments. Photodynamic Inactivation (PDI) may be an auxiliary therapeutic option for mucormycosis. Due to the lack of reports in the literature on the morphology and photodynamic inactivation of R. oryzae, characterization of the fungus using Confocal Microscopy and Transmission Electron Microscopy, and different protocols using Photodithazine® (PDZ), a chlorin e6 compound, as a photosensitizer, were performed. The fungus growth rate under different concentrations and incubation times of the photosensitizer and its association with the surfactant Sodium Dodecyl Sulphate (SDS) was evaluated. For the hyphae, both in the light and dark phases, in the protocols using only PDZ, no effective photodynamic response was observed. Meanwhile with the combination of SDS 0.05% and PDZ, inhibition growth rates of 98% and 72% were achieved for the white and black phase, respectively. In the conidia phase, only a 1.7 log10 reduction of the infective spores was observed. High concentration of melanin and the complex and resistant structures, especially at the black phase, results in a high limitation of the PDI inactivation response. The combined use of the SDS resulted in an improved response, when compared to the one obtained with the amphotericin B treatment.

Flow-through inactivation of pathogenic Escherichia coli by titanium suboxide reactive electrochemical membranes: Unlocking the coupled mechanics of electrochemical and subcellular alterations

Limited mass transfer controlled by diffusion and unexplored disinfection mechanisms at the subcellular alternation respond to different electrochemical reactions always obstacles the electrochemical disinfection decentralized water treatment. Here, a large-scale reactive electrode membrane composed of titanium suboxide (TiSO-REM) was pioneered for pathogen inactivation and mechanism exploration. Complete bacteria inactivation (>7.1 log reduction) was achieved after 20 min of electrolysis at 1440 L m−2 h−1 (LMH) and 15 mA cm−2. Electrostatic adsorption facilitated the interaction of pathogens with oxidants in the electrode boundary layer by enhancing the adhesion of Escherichia coli at anode surface, resulting in 25 % improvement in removal. Subcellular alternation of waterborne pathogens depended on specific electrochemical mechanisms. Direct electron transfer (DET) unbalanced intracellular metabolism by excessive intracellular reactive oxygen species accumulation. While more violent electro-generated •OH annihilated the whole cells with disorderly alternation which also effectively reduced the risk of bacterial regeneration with no bacterial resuscitation. The study also provides a universal model to develop sustainable technologies for pathogen inactivation and precise regulation of inactivation efficiency from a mechanistic perspective for a wide range of engineering applications like water disinfection and bio-safety control.

Delivery of endolysin across outer membrane of Gram-negative bacteria using translocation domain of botulinum neurotoxin

The emergence of multidrug-resistant pathogens has outpaced the development of new antibiotics, leading to renewed interest in endolysins. Endolysins have been investigated as novel biocontrol agents for Gram-positive bacteria. However, their efficacy against Gram-negative species is limited by the barrier presented by their outer membrane, which prevents endolysin access to the peptidoglycan substrate. Here, we used the translocation domain of botulinum neurotoxin to deliver endolysin across the outer membrane of Gram-negative bacteria. The translocation domain selectively interacts with and penetrates membranes composed of anionic lipids, which have been used in nature to deliver various proteins into animal cells. In addition to the botulinum neurotoxin translocation domain, we have fused bacteriophage-derived receptor binding protein to endolysins. This allows the attached protein to efficiently bind to a broad spectrum of Gram-negative bacteria. By attaching these target-binding and translocation machineries to endolysins, we aimed to develop an engineered endolysin with broad-spectrum targeting and enhanced antibacterial activity against Gram-negative species. To validate our strategy, we designed engineered endolysins using two well-known endolysins, T5 and LysPA26, and tested them against 23 strains from six species of Gram-negative bacteria, confirming that our machinery can act broadly. In particular, we observed a 2.32 log reduction in 30 min with only 0.5 µM against an Acinetobacter baumannii isolate. We also used the SpyTag/SpyCatcher system to easily attach target-binding proteins, thereby improving its target-binding ability. Overall, our newly developed endolysin engineering strategy may be a promising approach to control multidrug-resistant Gram-negative bacterial strains.

Tannic Acid Incorporated Antibacterial Polyethylene Glycol Based Hydrogel Sponges for Management of Wound Infections.

Conventional wound dressings fail to provide features that can assist the healing process of chronic wounds. Multifunctional wound dressings address this issue by incorporating attributes including antibacterial and antioxidant activity, and the ability to enhance wound healing. Herein, polyethylene glycol (PEG)-based antibacterial hydrogel sponge dressings are prepared by a rapid and facile gas foaming method based on an acid chloride/alcohol reaction where tannic acid (TA) is included as a reactant to impart antibacterial efficacy as well as to enhance the mechanical properties of the samples. The results reveal that the TA-integrated sponges possess excellent antibacterial properties against both Escherichia coli and Staphylococcus aureus with approximately 6-8 log reduction in the microbial colony count after 6h, indicating their high potential for management of infection-prone wounds. Compared to the control sample, TA incorporation increases the elastic modulus by twofold. As the samples also exhibit biocompatibility, antioxidant activity, and wound healing capacity, the novel TA-incorporated hydrogels can be an alternative to traditional wound dressings for wounds with low-to-moderate exudate.

Linalool Reduces Virulence and Tolerance to Adverse Conditions of Listeria monocytogenes.

Listeria monocytogenes, a foodborne pathogen causing listeriosis, poses substantial societal, economic, and public health challenges due to its resistance, persistence, and biofilm formation in the food industry. Exploring subinhibitory concentrations of compounds to target virulence inhibition and increase susceptibility to adverse conditions presents a promising strategy to mitigate its impact of L. monocytogenes and unveils new potential applications. Thus, this study aims to explore the effect of linalool on virulence factors of L. monocytogenes and potential use in the reduction in its tolerance to stressful conditions. This action was analysed considering the use of two sub-inhibitory concentrations of linalool, 0.312 and 0.625 mg/mL. We found that even with the lowest tested concentrations, a 65% inhibition of violacein production by Chromobacterium violaceum, 55% inhibition in biofilm formation by L. monocytogenes and 62% reduction on haemolysis caused by this bacterium were observed. In addition to its impact on virulence factors, linalool diminished the tolerance to osmotic stress (up to 4.3 log reduction after 24 h with 12% NaCl), as well as to high (up to 3.8 log reduction after 15 min at 55 °C) and low temperatures (up to 4.6 log reduction after 84 days with 12% NaCl at 4 °C). Thus, this study paves the way to further investigation into the potential utilization of linalool to mitigate the threat posed by L. monocytogenes in the field of food safety and public health.

Characterization of slightly acidic electrolyzed water on effective disinfection against microbial safety and retention of phenolic compound in SAEW treated fresh romaine lettuce

Abstract This study investigated the effects of processing parameters, specifically the low rate and the combination of diluted HCl and salt (NaCl) at different concentrations, on the properties of the slightly acidic electrolyzed water (SAEW) that was produced. The properties of the SAEW that were analyzed included pH, oxidation-reduction potential (ORP), available chlorine concentrations (ACC), and generated hypochlorous acid (HClO) concentration. NaCl alone resulted in the lowest pH (&amp;lt;4) and the highest ORP values (&amp;gt;1000 mV). Increasing HCl concentrations significantly raised pH levels to greater than 5 and lowered ORP values of SAEW, with the highest pH (5.7) observed with 1.5% HCl and 5% NaCl. The highest HClO concentration of 19.65±1.03 mg/L was obtained with 1.5% HCl:5% NaCl. Interestingly, the concentration of NaCl showed no significant effects on the production of HClO. Furthermore, different concentrations of combined NaCl and HCl significantly influenced the inactivation efficiency on total aerobic bacteria count and changes in phenolic compound content. Increasing HCl concentrations from 0.5% to 2.0% led to an increase in the reduction of aerobic bacteria counts from 2.51 to 4.22 log CFU/g with 5% NaCl and from 2.49 to 3.52 log CFU/g with 10% NaCl. Flow rates significantly contributed to the change in HClO formation and altered the properties of the produced SAEW. Results indicated that SAEW treatment significantly reduced total aerobic bacteria counts. The lower flow rates (0.3 L/min) produced the highest log reductions. Additionally, SAEW treatment led to a reduction in phenolic content, even though considerable amount was retained at lower HClO concentrations. These findings offer valuable information on optimizing SAEW treatment protocols for enhancing microbial safety and extending the shelf life of fresh produce, while considering the impact on the content of phenolic compounds.

Impact of intense sanitization procedures on bacterial communities recovered from floor drains in pork processing plants.

Pork processing plants in the United States (US) cease operations for 24-48 h every six or twelve months to perform intense sanitization (IS) using fogging, foaming, and further antimicrobial treatments to disrupt natural biofilms that may harbor pathogens and spoilage organisms. The impact such treatments have on short-term changes in environmental microorganisms is not well understood, nor is the rate at which bacterial communities return. Swab samples were collected from floor drains to provide representative environmental microorganisms at two US pork processing plants before, during, and after an IS procedure. Samples were collected from four coolers where finished carcasses were chilled and from four locations near cutting tables. Each sample was characterized by total mesophile count (TMC), total psychrophile count (TPC), and other indicator bacteria; their biofilm-forming ability, tolerance of the formed biofilm to a quaternary ammonium compound (300 ppm, QAC), and ability to protect co-inoculated Salmonella enterica. In addition, bacterial community composition was determined using shotgun metagenomic sequencing. IS procedures disrupted bacteria present but to different extents depending on the plant and the area of the plant. IS reduced TPC and TMC, by up to 1.5 Log10 CFU only to return to pre-IS levels within 2-3 days. The impact of IS on microorganisms in coolers was varied, with reductions of 2-4 Log10, and required 2 to 4 weeks to return to pre-IS levels. The results near fabrication lines were mixed, with little to no significant changes at one plant, while at the other, two processing lines showed 4 to 6 Log10 reductions. Resistance to QAC and the protection of Salmonella by the biofilms varied between plants and between areas of the plants as well. Community profiling of bacteria at the genus level showed that IS reduced species diversity and the disruption led to new community compositions that in some cases did not return to the pre-IS state even after 15 to 16 weeks. The results found here reveal the impact of using IS to disrupt the presence of pathogen or spoilage microorganisms in US pork processing facilities may not have the intended effect.

Evaluation of 1,9-Dimethyl-Methylene Blue nanoencapsulation using rhamnolipid nanoparticles to potentiate the Photodynamic Therapy technique in Candida albicans: In vitro study

With the rapid development of nanotechnology, various functional nanomaterials have shown exciting potential in biomedical areas such as drug delivery, antitumor, and antibacterial therapy. These nanomaterials improve the stability and selectivity of loaded drugs, reduce drug-induced side effects, realize controlled and targeted drug release, and increase therapeutic efficacy. The increased resistance to antifungal microbicides in medical practice and their side effects stimulate interest in new therapies, such as Photodynamic Therapy (PDT), which do not generate resistance in microorganisms and effectively control the pathology. The present study aimed to evaluate, in vitro, the efficacy of photodynamic therapy on Candida albicans using 1,9-Dimethyl-Methylene Blue (DMMB) as photosensitizer, red LED (λ630), and nanoencapsulation of DMMB (RL-NPs/DMMB) using rhamnolipids produced by Pseudomonas aeruginosa to evaluate if there is better performance of DMMB + RL particles compared to DMMB alone via the characterization of DMMB + RL and colony forming count. The tests were carried out across six experimental groups (Control, DMMB, RL-NPs, RL-NPs/DMMB, PDT and PDT + RL-NPs/DMMB) using in the groups with nanoparticles, DMMB (750 ng/mL) encapsulated with rhamnolipids in a 1:1 ratio, the light source consisted of a prototype built with a set of red LEDs with an energy density of 20 J/cm2. The results showed that applying PDT combined with encapsulation (RL-NPs/DMMB) was a more practical approach to inhibit Candida albicans (2 log reduction) than conventional applications, with a possible clinical application protocol.

Synergistic efficacy of ultrasound and ammonium persulfate in inactivating Escherichia coli O157:H7 in buffered peptone water and orange juice

This study investigated the synergistic effects of ammonium persulfate (PS) and ultrasound (US) on the inactivation of Escherichia coli O157:H7 in buffered peptone water (BPW) and orange juice products. A comprehensive assessment of PS concentrations ranging from 1 to 300 mM, considering not only the statistical significance but also the reliability and stability of the experimental outcomes, showed that 150 mM was the optimal PS concentration for the inactivation of E. coli O157:H7. Additionally, US output intensities varying from 30 % to 60 % of the maximum US intensity were evaluated, and 50 % US amplitude was found to be the optimal US condition. A 50 % amplitude setting on the sonicator corresponds to half of its maximum displacement, approximately 60 μm, based on a maximum amplitude of 120 μm. The inactivation level of E. coli O157:H7 was significantly enhanced by the combined treatment of PS and US, compared to each treatment of PS and US alone. In the BPW, a 10-min treatment with the combination of PS and US resulted in a significant synergistic inactivation, achieving up to a log reduction of 3.86 log CFU/mL. Similarly, in orange juice products, a 5-min treatment with the combination of PS and US yielded a significant synergistic inactivation, with a reduction reaching 5.90 log CFU/mL. Although the treatment caused a significant color change in the sample, the visual differences between the treated and non-treated groups were not pronounced. Furthermore, the combined treatment in orange juice demonstrated significantly enhanced antimicrobial efficacy relative to BPW. Despite identical 5-min treatment periods, the application in orange juice resulted in a substantially higher log reduction of E. coli O157:H7, achieving 7.16 log CFU/mL at a reduced PS concentration of 30 mM, whereas the same treatment in BPW yielded only a 2.89 log CFU/mL reduction at a PS concentration of 150 mM, thereby highlighting its significantly superior antimicrobial performance in orange juice. The mechanism underlying microbial inactivation, induced by the combined treatment of PS and US, was identified as significant cell membrane damage. This damage is mediated by sulfate radicals, generated through the sono-activation of persulfate. In addition, the low pH of orange juice, measured at 3.7, is likely to have further deteriorated the E. coli O157:H7 cells compared to BPW (pH 7.2), by disrupting their cell membranes, proton gradients, and energy metabolism. These findings underscore the effectiveness of PS and US integration as a promising approach for non-thermal pasteurization in the food industry. Further research is needed to optimize treatment parameters and fully explore the practical application of this technique in large-scale food processing operations. Sensory evaluation and nutritional assessment are also necessary to address the limitations of PS.