Effect of DMPEI coating against biofilm formation on PVC catheter surface.

Urinary tract infections (UTIs) are a significant cause of morbidity in healthcare systems and are prominently associated with applying urethral catheters, particularly in surgeries. Polyvinyl chloride (PVC) is extensively utilized in the fabrication of catheters. Biofilms, complex polymeric constructions, provide a protective milieu for cell multiplication and the enhancement of antibiotic resistance. Strategies to counteract biofilm development on medical apparatuses' surfaces incorporate antimicrobial agents such as N,N-dodecyl, and methyl polyethylenimine (DMPEI). This research endeavored to characterize the morphology of PVC and PVC-DMPEI surfaces utilizing Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) and to gauge hydrophobicity through contact angle measurements. Employing Escherichia coli, Staphylococcus aureus, and Candida albicans in adhesion assays enabled the assessment of DMPEI's efficacy in preventing microbial adherence to PVC. Butanol successfully solubilized 2 mg.mL-1 DMPEI without altering the PVC structure. SEM results substantiated the formation of a DMPEI layer on the PVC surface, which led to decreased surface roughness, as validated by AFM, and increased hydrophilicity, as demonstrated by contact angle evaluations. E. coli, S. aureus, and C. albicans exhibited significant adhesion reduction, 89.3%, 94.3%, and 86.6% on PVC-DMPEI surfaces. SEM visualizations confirmed reduced cellular colonization on PVC-DMPEI and highlighted considerable morphological modifications in E. coli. Consequently, DMPEI films effectively minimize the adhesion of E. coli, S. aureus, and C. albicans on PVC surfaces. DMPEI, with its potential as a protective coating for innovative medical devices, promises to inhibit biofilm adherence effectively.

Ohmic heating as a method of obtaining paraprobiotics: Impacts on cell structure and viability by flow cytometry.

This study aimed to evaluate the effects of ohmic heating (OH) on probiotic inactivation, cell viability and morphology of the probiotic strains Lactobacillus acidophilus LA 05 (LA), Lacticaseibacillus casei 01 (LC), and Bifidobacterium animalis Bb 12 (BA) to develop paraprobiotics. OH at different electric field magnitudes (4, 8, and 12 V/cm at 60 Hz) and conventional heat treatment (CONV) were performed to determine the most adequate condition for the obtainment of paraprobiotics. Analysis of culturability, flow cytometry (FC), and Scanning electron microscope (SEM) was carried out. The complete inactivation by CONV was achieved only in the following conditions: LA - 95 °C/5 min, LC and BA - 95 °C/7 min. The same temperature profile was used in OH treatments to study the OH electrical effects. The OH treatment (8 V/cm) caused lower damage to the cell membrane integrity compared to the CONV treatment (p < 0.05). The OH showed to be adequate technology for the efficient production of paraprobiotics.

Ohmic heating increases inactivation and morphological changes of Salmonella sp. and the formation of bioactive compounds in infant formula.

The effect of ohmic heating (OH) (50, 55, and 60 °C, 6 V/cm) on the inactivation kinetics (Weibull model) and morphological changes (scanning electron microscopy and flow cytometry) of Salmonella spp. in infant formula (IF) was evaluated. In addition, thermal load indicators (hydroxymethylfurfural and whey protein nitrogen index, HMF, and WPNI) and bioactive compounds (DPPH, total phenolics, ACE, α-amylase, and α-glucosidase inhibitory activities) were also studied. OH presented a more intense inactivation rate than conventional heating, resulting in a reduction of about 5 log CFU per mL at 60 °C in only 2.91 min, being also noted a greater cell membrane deformation, higher formation of bioactive compounds, and lower values for the thermal load parameters. Overall, OH contributed to retaining the nutritional value and improve food safety in IF processing.

Can sucrose-substitutes increase the antagonistic activity against foodborne pathogens, and improve the technological and functional properties of sheep milk kefir?

The effect of different types of sugar (sucrose, demerara, brown, fructose, coconut sugar, and honey) on sheep milk kefir was evaluated. Microbial counts (Lactobacillus, Lactococcus, Leuconostoc, yeast), antagonistic activity against foodborne pathogens, microstructure (scanning electron microscopy), and antiproliferative activity of cancer cells were evaluated. Furthermore, the antioxidant activity (DPPH), inhibitory activity of angiotensin-converting enzyme (ACE), α-amylase, and α-glucosidase, lactose content, lactic and acetic acids and ethanol, fatty acid profile and volatile organic compounds were determined. The addition of sugars increased the Lactobacillus population (up to 2.24 log CFU/mL), metabolites concentration, antagonistic activity against pathogens, antioxidant activity (11.1 to 24.1%), ACE inhibitory activity (27.5 to 37.6%), α-amylase inhibition (18 to 37.4%), and anti-proliferative activity. Furthermore, it improved the fatty acid profile and volatile compounds. The results suggest that the replacement of sucrose with different types of sugar constitute an interesting option to be used in sheep milk kefir formulations.

Corrigendum: Quantifying the Responses of Three Bacillus cereus Strains in Isothermal Conditions and During Spray Drying of Different Carrier Agents.

[This corrects the article on p. 1113 in vol. 9, PMID: 29904375.].

Quantifying the Responses of Three Bacillus cereus Strains in Isothermal Conditions and During Spray Drying of Different Carrier Agents.

Spray drying is a widely used method for producing milk powder. This process is not aimed to cause microbial inactivation, thus sporeforming bacteria may be abundant in the microbiota of milk powder. The first aim of this study was to determine the inactivation kinetics parameters in capillary tubes of three Bacillus cereus strains (436, B63, 540) in three menstrua (whole milk, phosphate buffer, and talc suspension) at 90, 100, and 110°C. D-values for B. cereus in the three menstrua were not significantly different at the highest tested temperature (p > 0.05). Thus, talc was chosen as a carrier agent to allow the recovery of B. cereus from spray dried materials given its low interference on inactivation kinetics. B. cereus spores were also inoculated in whole milk and skim milk following spray drying at 95, 105, and 110°C (outlet temperature). After the spray drying runs, B. cereus spores were counted and the number of decimal reductions (γ) calculated. A correlation between the small diameter of the particles with the survival of spores of three B. cereus strains was found, and B. cereus 436 presented consistently the lowest γ no matter temperature and a carrier agent. The highest γ was found when talc powder was used, which suggest that this carrier agent does not protect B. cereus spores during spray drying. Spray drying of milk can lead to up to 4 γ (strain 540) of B. cereus spores but depending on the strain less than one γ (strain 436) could be observed. This study contributes to the knowledge on the microbiology of low water activity foods by providing novel findings regarding the fate of three B. cereus strains to different spray drying conditions. Acknowledging the variability of inactivation of B. cereus during spray drying is key in the current context of food safety in which the quantification of effects of unit operations must be known for the validation of processes and development of more robust formulations.

The addition of inulin and Lactobacillus casei 01 in sheep milk ice cream.

The effect of the Lactobacillus casei 01 and inulin addition on sheep milk ice cream during storage (-18 °C, 150 days) was investigated. Control, probiotic and synbiotic ice cream (10% w/w sheep milk cream; 10% w/w sheep milk cream, L. casei 01, 6 log CFU/mL; 10% w/w inulin, L. casei 01, 6 log CFU/mL, respectively) were manufactured. Microbiological counts (probiotic count, survival after in vitro gastrointestinal resistance, Caco-2 cell adhesion), bioactivity and microstructure were analysed. Physical and textural characteristics, colour parameters, thermal analysis and organic acids/volatile compounds were also evaluated. All formulations supported L. casei 01 viability and maintained above the minimum therapeutic level (>6 log CFU/mL) during storage. Inulin did not affect L. casei 01 survival after the passage through simulated gastrointestinal tract and adhesion to Caco-2 cells while improved the ACE-inhibitory and antioxidant activity. L. casei 01 addition produced several volatile compounds, such as carboxylic acids, alcohols, aldehydes and ketones. Also, scanning electron microscopy showed an interaction between probiotic bacteria and inulin fibre on synbiotic ice cream and the adhesion of L. casei to Caco-2 cells was observed.

Nanoscopic Localization of Surface-Exposed Antigens of Borrelia burgdorferi.

Borrelia burgdorferi sensu lato, the causative agent of Lyme disease, is transmitted to humans through the bite of infected Ixodes spp. ticks. Successful infection of vertebrate hosts necessitates sophisticated means of the pathogen to escape the vertebrates' immune system. One strategy employed by Lyme disease spirochetes to evade adaptive immunity involves a highly coordinated regulation of the expression of outer surface proteins that is vital for infection, dissemination, and persistence. Here we characterized the expression pattern of bacterial surface antigens using different microscopy techniques, from fluorescent wide field to super-resolution and immunogold-scanning electron microscopy. A fluorescent strain of B. burgdorferi spirochetes was labeled with monoclonal antibodies directed against various bacterial surface antigens. Our results indicate that OspA is more evenly distributed over the surface than OspB and OspC that were present as punctate areas.

Sugarcane cell wall structure and lignin distribution investigated by confocal and electron microscopy.

Lignocellulosic plant cell wall is considered a potential source for second generation biofuels. The plant cell wall is a highly complex structure mainly composed of cellulose, hemicelluloses, and lignin that form a network of crosslinked fibers. The structural organization of the sugarcane cell wall has not been previously analyzed in detail, and this analysis is a prerequisite for further studies on the recalcitrance and deconstruction of its biomass. In this work, cellulose and lignin localization were investigated by confocal laser scanning microscopy. In addition, the internode sugarcane cell wall structural organization was analyzed by electron microscopy. Internode stem anatomy showed a typical monocot structure consisting of epidermis, hypoderm, and vascular bundles scattered throughout ground parenchyma tissue and surrounded by sclerenchyma fibers. Confocal images of safranin labeled sugarcane showed that lignin distribution was predominant in the vessel elements, cell wall corners (CC), and middle lamella (ML), while cellulose-rich cell walls were randomly distributed in the ML and organized in the other cell wall layers. KMnO4 cytochemistry revealed that lignin was predominantly distributed in secondary cell walls, ML and CC. Cell wall sublayers (S1, S2, and S3) were identified and measured by transmission electron microscopy. Our results provide insights that may help further understanding of sugarcane cell wall organization, which is crucial for the research and technology of plant-based biofuel production.

Structural evaluation of sugar cane bagasse steam pretreated in the presence of CO2 and SO2.

BACKGROUND: Previous studies on the use of SO2 and CO2 as impregnating agent for sugar cane bagasse steam treatment showed comparative and promising results concerning the cellulose enzymatic hydrolysis and the low formation of the inhibitors furfural and hydroxymethylfurfural for the use of CO2 at 205°C/15 min or SO2 at 190°C/5 min. In the present study sugar cane bagasse materials pretreated as aforementioned were analyzed by scanning and transmission electron microscopy (SEM and TEM), X-Ray Diffraction (XRD) and Infrared (FTIR spectroscopy) aiming a better understanding of the structural and chemical changes undergone by the pretreated materials. RESULTS: SEM and TEM data showed that the structural modifications undergone by the pretreatment with CO2 were less pronounced in comparison to that using SO2, which can be directly related to the combined severity of each pretreatment. According to XRD data, untreated bagasse showed, as expected, a lower crystallinity index (CI = 48.0%) when compared to pretreated samples with SO2 (CI = 65.5%) or CO2 (CI = 56.4%), due to the hemicellulose removal of 68.3% and 40.5%, respectively. FTIR spectroscopy supported SEM, TEM and XRD results, revealing a more extensive action of SO2. CONCLUSIONS: The SEM, TEM, XRD and FTIR spectroscopy techniques used in this work contributed to structural and chemical analysis of the untreated and pretreated bagasse. The images from SEM and TEM can be related to the severity of SO2 pretreatment, which is almost twice higher. The crystallinity index values obtained from XRD showed that pretreated materials have higher values when compared with untreated material, due to the partial removal of hemicellulose after pretreatment. FTIR spectroscopy supported SEM, TEM and XRD results. CO2 can actually be used as impregnating agent for steam pretreatment, although the present study confirmed a more extensive action of SO2.