Resistance Enzymes Research Articles

Phenotypic and Molecular Characterization of Extended-Spectrum β-Lactamase, Plasmid-Mediated- AmpC, and Carbapenemase-Producing Enterobacteriaceae Isolated from Companion and Production Animals in Brazil.

The crisis of bacterial resistance is an emerging One Health challenge, driven by the overuse of antimicrobials in medical and agricultural settings. This study aimed to investigate extended-spectrum β-lactamase (ESBL), Ampicillinase (AmpC), and carbapenemase production, and the presence of genes encoding these enzymes in Escherichia coli, Klebsiella spp., and Proteus spp., major contributors to infections and resistance isolates from animals. From 2016 to 2021, 130 multidrug-resistant (MDR) or extensively drug-resistant (XDR) isolates were recovered from the secretions, excretions, and organs of companion and production animals with active infections. Antibacterial sensitivity tests, along with phenotypic and genotypic detection of resistance enzymes, were performed. To the best of our knowledge, this is the first study in Brazil to estimate the prevalence of XDR Enterobacteriales isolated from companion and production animals, which accounted for 13.8% of the strains. Statistically significant differences (P < 0.05) in resistant bacteria between different classes and within the same class of antibacterial bacteria were found. The statistical probability between genotypic detection of ESBL (OR = 3.1) and phenotypic tests for AmpC (OR = 2.3) was also established. Approximately 32.3%, 17.6%, and 16.8% of the strains had positive phenotypic tests for ESBL, AmpC, and carbapenemases, respectively. Genetic analysis revealed the presence of blaCTX-M (60.0%), blaAmpC (9.18%), blaKPC-2 (0.76%), and blaNDM (1.52%). AmpC genes were identified in 8.46% of the samples, with blaCMY being the most frequent (6.92%), followed by blaDHA (0.77%), and blaFOX (0.77%). The sequenced amplicons were deposited in NCBI. This study reveals critical data on Enterobacteriaceae with antibacterial resistance genes isolated from animals and may pose a significant threat to One health.

Enhancing enzymatic resistance of pea type 3 resistant starch through pressure heating and annealing.

Type III resistant starch (RS3) is an important functional food ingredient. In this study, RS3 was prepared by retrogradation of pea starch after acid hydrolysis and pullulanase debranching. Heat-moisture treatments, including annealing (90°C, 40-70% moisture content) and pressure heating (121°C, 10-40% moisture content), were employed to further enhance the RS content of pea RS3. The relationship between the structural changes and digestibility of pea RS3 was investigated. The results showed significant increases in relative crystallinity, particle size, gelatinization temperature, and RS content, while swelling power, pasting viscosity, and rapidly digestible starch content were markedly decreased after heat-moisture treatment. A strong positive correlation (r=0.94*) was observed between relative crystallinity and RS content. The highest RS content of 85.6% was achieved after pressure heating at 20% moisture content, which was notably higher than the 45.6% RS content before heat-moisture treatment. This study highlights the beneficial effects of annealing and pressure heating in enhancing RS content in pea RS3, providing valuable insights for developing RS3 with high RS content after cooking.

Study on the Optimal Harvesting Age of Astragalus Mongholicus Under Wild-Simulated Cultivation in Inner Mongolia

The harvesting age is a critical factor influencing the quality of medicinal crops, as it significantly affects the content of active compounds and clinical efficacy, which vary across different cultivation years. This study aims to clarify the growth and development patterns of wild-simulated and cultivated Astragalus mongholicus at different ages and provide theoretical and practical guidance for determining its optimal harvesting age. The morphological indicators, photosynthetic performance, stress resistance enzyme activities, medicinal compounds, and yields of Astragalus mongholicus cultivated and wild-simulated for one, two, three, and four years were analyzed. Results showed that the harvesting age influenced the various measurement indicators of wild-simulated Astragalus mongholicus. The underground growth of the two-year-old plants was the most vigorous, with a stronger photosynthetic capacity and the highest content of calycosin-7-O-glucoside. Both two-year-old and three-year-old plants exhibited higher superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) enzyme activities. The three-year-old plants had the highest astragaloside IV content and the greatest economic benefit. Considering both the quality of the medicinal material and the economic returns, this study suggests that the optimal harvesting age for wild-simulated cultivated Astragalus mongholicus in Inner Mongolia is three years, though harvesting at two years may also be feasible under practical conditions.

Bioefficacy and persistent toxicity of newer insecticide against thrips, Pseudodendrothrips mori (Niwa) and leaf webber, Diaphania pulverulentalis (Hampson) in mulberry cultivation

Two field trials were conducted in two locations to assess new insecticide molecules' efficacy against thrips and leaf webber in the mulberry ecosystem. Results indicated that fipronil 5SC @ 50 g a.i. /ha showed the highest percentage reduction in the population of thrips (87.13 and 88.41 % in the first and second trials, respectively) over untreated control. In contrast, for leaf webber, flubendiamide 39.35 SC @ 48 g a.i./ha showed the highest effectiveness with 85.56 and 89.90 per cent reduction over control in the first and second trials, respectively. Persistence was observed through laboratory bioassay. Results revealed that the order of persistent toxicity of insecticides against thrips based on persistent toxicity index was fipronil 5 SC &gt; spinetoram 11.7 SC &gt; thiacloprid 21.7 SC &gt; dimethoate 30 EC. Emamectin benzoate 5SC and dimethoate 30 EC recorded the shortest persistency of 10 days after treatment against mulberry leaf Webber, while chlorantraniliprole 18.5 SC and flubendiamide 39.35 SC registered the longest persistency of 25 and 20 days, respectively at the recommended dose. Higher concentrations of pest–resistant proteins and enzymes were recorded in the insecticide-treated mulberry plants than in the untreated plants. To conclude, fipronil 5 SC and thiacloprid 21.7 SC were the most effective in checking the population of thrips. At the same time, emamectin benzoate 5SC and flubendiamide 39.35 SC were most efficient against leaf webber, besides having less persistent toxicity than other treatments. Hence, these insecticides may be recommended to manage thrips and leaf webber in the mulberry ecosystem.

Efficacy and Safety of Aerosol Inhalation of Colistin Sulfate for the Treatment of Carbapenem-Resistant Klebsiella pneumoniae Infection in the Peri-Operative Period of Liver Transplantation: A Single-Center Retrospective Study.

Objective: This study intended to evaluate the clinical efficacy and safety of colistin sulfate aerosol inhalation in combination with ceftazidime-avibactam for the treatment of pulmonary carbapenem-resistant Klebsiella pneumoniae (CRKP) infection during the peri-operative period of liver transplantation. Materials and Methods: A retrospective analysis was designed to investigate 52 patients who developed pulmonary CRKP infection after liver transplantation between December 1, 2019, and November 30, 2022. On the basis of whether they received colistin sulfate aerosol inhalation, the patients were divided into the treatment group (n = 29) and the control group (n = 23). The baseline information, infection status, CRKP enzyme type, inflammatory markers, liver and kidney function, and prognosis were compared and analyzed. Results: There were no significant differences in patient characteristics, infection status, and drug resistance enzyme type between the treatment group (treated with colistin sulfate aerosol inhalation and ceftazidime and avibactam sodium for injection) and the control group (treated with ceftazidime and avibactam sodium for injection alone). Colistin sulfate aerosol inhalation treatment reduced concentrations of inflammatory markers, with post-treatment white blood cell count, procalcitonin, and C-reactive protein significantly lower than pre-treatment levels (p < 0.05). Except for C-reactive protein at 14 days (p = 0.032), the two groups had no significant differences in other indicators. There were no significant differences in alanine aminotransferase, aspartate aminotransferase, total bilirubin, and glomerular filtration rate after treatment, indicating no discernible alteration in liver and kidney function. In addition, the treatment group took a significantly shorter time to normalize body temperature compared with the control group (p = 0.025), but there were no significant differences in the cure with no colonization rate and all-cause mortality rate between the two groups. Conclusions: The combination of colistin sulfate aerosol inhalation and ceftazidime and avibactam sodium for injection is effective in treating pulmonary CRKP infection during the peri-operative period of liver transplantation. It does not impose an additional burden on liver and kidney function, providing a new treatment option for this type of infection.

Exploring the GSTP1 inhibition potential of photosensitizer compounds for enhanced cancer treatment in photodynamic therapy.

Photodynamic therapy (PDT) has gained considerable attention in cancer treatment due to its non-invasive nature and the ability of photosensitizers to generate reactive oxygen species upon light activation, leading to tumor destruction. Glutathione S-transferase P1 (GSTP1) is a key enzyme in chemotherapy resistance, often overexpressed in various cancers, and its inhibition of GSTP1 presents a promising strategy to enhance cancer treatment. This study is aimed at assessing the potential of prominent photosensitizers as GSTP1 inhibitors through molecular docking analysis to strengthen the efficacy of PDT. The photosensitizers were docked into the active site of GSTP1, and their binding affinities, inhibition constants (Ki), and molecular interactions were assessed. Among the tested photosensitizers, zinc phthalocyanine, hypericin, and temoporfin emerged as the top candidates, exhibiting binding energies of - 10.8, - 10.2, and - 9.8kcal/mol, along with Ki values of 0.012, 0.033, and 0.064µM, respectively. These compounds outperformed the reference inhibitor ethacrynic acid, which had a binding energy of - 6.6kcal/mol and a Ki of 14.35µM. These findings suggest that the dual action of these photosensitizers provides a promising strategy for combating cancer and overcoming treatment resistance.

Improvement of biochemical characteristics of tetracycline-contaminated soil for stimulating soybean growth using Arbuscular mycorrhizal fungi.

Tetracycline (TC), as a new type of environmental pollutant, poses a great threat to human food safety and health, thus becoming the focus of human environmental protection issues. In this study, we selected an environmentally friendly microbial remediation method to degrade the residual TC in soil. An experiment was conducted with Funneliformis mosseae (F. mosseae) and artificial TC-contaminated soil to analyze the physiology, antimicrobial enzyme activities, and TC residues in soybean plants and rhizomatous soil. The results showed that the presence of TC in the soil inhibited the enzyme activities of soybean root system and soil, and suppressed the biomass of soybean. Inoculation of F. mosseae in TC-contaminated soil promoted the degradation of TC in the soil, enhanced soil resistance enzyme and urease activities (12.53-43.48%) around the root soil, and enhanced the soil resistance enzymes and promoted the uptake of nutrients in the soybean root system.We conclude that F. mosseae may reduce antibiotics or promote nutrient uptake to enhance plant resistance by altering inter-root enzyme activity. Therefore, this study provides a new theoretical basis for using AMF to remediate TC-contaminated soil and retard the stress of TC on the growth of soybean.

Cardenolides in Asclepias syriaca Seeds: Exploring the Legacy of Tadeus Reichstein.

The common milkweed Asclepias syriaca is widespread in North America and produces cardenolide toxins that deter herbivores by targeting the transmembrane enzyme Na+/K+-ATPase. In 1979, Nobel Laureate Tadeus Reichstein elucidated the structure of novel cardenolides isolated from A. syriaca roots and proposed structures for several other cardenolides that could not be confirmed. In this study, we investigate the cardenolide composition of A. syriaca seeds, focusing on their abundance and in vitro inhibitory potency on the sensitive porcine Na+/K+-ATPase and that of the highly resistant large milkweed bug, Oncopeltus fasciatus. We identify five previously unreported cardenolides (1-5), three of which are predominantly found in seeds, in addition to the known syrioside (6), aspecioside (7), and the 2-thiazoline ring-containing cardenolide labriformin (8). Glucopyranosyl-allomethylosyl-12-deoxy aspecioside (5) is distinguished by lack of oxidation at C-12, and compounds 2, 3, 6, and 8 contain a rare 1,4-dioxane motif. Inhibitory efficacy of the isolated cardenolides for sensitive and resistant enzymes appears to be correlated. Finally, we confirmed the structure of compound 2, originally proposed by Tadeus Reichstein, and are pleased to share his original 1979 handwritten manuscript.

Antifungal Properties of Bioactive Compounds Isolated from Fucus vesiculosus Supercritical Carbon Dioxide Extract.

The exploration of natural antifungal substances from algal origins is significant due to the increasing resistance of pathogens to conventional antifungal agents and the growing consumer demand for natural products. This manuscript represents the inaugural investigation into the antifungal attributes of bioactive compounds extracted from Fucus vesiculosus via supercritical carbon dioxide (scCO2) extraction utilizing contemporary countercurrent chromatography (CCC). In aligning with the prospective utilization of this extract within the agricultural sector, this study also serves as the preliminary report demonstrating the capability of Fucus vesiculosus scCO2 extract to enhance the activity of plant resistance enzymes. The fractions obtained through CCC were subjected to evaluation for their efficacy in inhibiting the macrospores of Fusarium culmorum. The CCC methodology facilitated the successful separation of fatty acids (reaching up to 82.0 wt.% in a given fraction) and fucosterol (attaining up to 79.4 wt.% in another fraction). All CCC fractions at the concentration of 1.0% were found to inhibit 100% of Fusarium culmorum growth. Moreover, Fucus vesiculosus scCO2 extract was able to activate plant resistance enzymes (Catalase, Ascorbic Peroxidase, Guaiacol Peroxidase, Phenylalanine Ammonia-Lyase, and Phenylalanine Ammonia-Lyase Activity).

Locking up G‐Quadruplexes with Light‐Triggered Staples Leads to Increased Topological, Thermodynamic, and Metabolic Stability

AbstractG‐quadruplexes (G4 s) are secondary, tetraplexed DNA structures abundant in non‐coding regions of the genome, implicated in gene transcription processes and currently firmly recognised as important potential therapeutic targets. Given their affinity for human proteins, G4 structures are investigated as potential decoys and aptamers. However, G4 s tend to adopt different conformations depending on the exact environmental conditions, and often only one displays the specifically desired biological activity. Their less intensively studied counterparts, the elusive tetraplexed intercalated‐motifs (IMs) are typically unstable at neutral pH, hampering the investigation of their potential involvement in a biological context. We herein report on a photochemical method for “stapling” such tetraplexed‐structures, to increase their stability, lock their topology and enhance their enzymatic resistance, while maintaining biological activity. The chemical structure and topology of the stapled Thrombin Binding Aptamer (TBA) was spectroscopically characterised and rationalised in silico. The method was then extended to other biologically relevant G4‐ and IM‐prone sequences, hinting towards potential application of such stapled structures in a therapeutic context.

Locking up G-Quadruplexes with Light-Triggered Staples Leads to Increased Topological, Thermodynamic, and Metabolic Stability.

G-quadruplexes (G4 s) are secondary, tetraplexed DNA structures abundant in non-coding regions of the genome, implicated in gene transcription processes and currently firmly recognised as important potential therapeutic targets. Given their affinity for human proteins, G4 structures are investigated as potential decoys and aptamers. However, G4 s tend to adopt different conformations depending on the exact environmental conditions, and often only one displays the specifically desired biological activity. Their less intensively studied counterparts, the elusive tetraplexed intercalated-motifs (IMs) are typically unstable at neutral pH, hampering the investigation of their potential involvement in a biological context. We herein report on a photochemical method for "stapling" such tetraplexed-structures, to increase their stability, lock their topology and enhance their enzymatic resistance, while maintaining biological activity. The chemical structure and topology of the stapled Thrombin Binding Aptamer (TBA) was spectroscopically characterised and rationalised in silico. The method was then extended to other biologically relevant G4- and IM-prone sequences, hinting towards potential application of such stapled structures in a therapeutic context.

Flavin-Dependent Monooxgenase Confers Resistance to Chlorantraniliprole and Spinetoram in the Rice Stem Borer Chilo suppressalis Walker (Lepidoptera: Crambidae).

Understanding the role of flavin-containing monooxygenases (FMOs) in the genetic mechanisms of insecticide resistance is essential for developing effective management strategies against the rice stem borer, Chilo suppressalis. In this study, we identified five FMO genes in C. suppressalis, examined their expression patterns, and revealed overexpression of FMO3B and FMO3C in field populations resistant to multiple insecticides, including chlorantraniliprole and spinetoram. Functional characterization using transgenic Drosophila indicated that FMO3B and FMO3C do not confer resistance to abamectin or methoxyfenozide but do mediate resistance to chlorantraniliprole and spinetoram. Knockdown of FMO3B and FMO3C increased sensitivity to these insecticides in C. suppressalis. Molecular docking studies indicated direct binding of chlorantraniliprole and spinetoram to these FMOs, underscoring their role in metabolic resistance. These findings indicate that FMOs are key enzymes in the metabolic resistance of C. suppressalis to chlorantraniliprole and spinetoram, enhancing our understanding of insecticide resistance and aiding the development of management strategies.

Impact of encapsulation conditions on V-type granular starch-curcumin complexes

V-type granular starch (VGS) could be a potential carrier of active substances according to previous research. Its hydrophobic cavity is capable of encapsulating and accommodating guest molecules with hydrophobicity. This study investigates the impact of various encapsulation conditions on curcumin payload capacity, encapsulation efficiency, and composite index, revealing that the optimal conditions for curcumin encapsulation using VGS were an encapsulation temperature of 60 °C, a curcumin addition ratio of 20% (w/w), a reaction duration of 1 h, and an ethanol solution volume of 40% (v/v). This observation is attributed to the hydrophobic capacity of VGS and the environmental sensitivity of curcumin. Furthermore, the initial temperature of thermal decomposition and the maximum weight loss rate temperature occurs for the complex are higher than those of VGS, curcumin, and the physical blend. In the enzymatic resistance experiments, the resistant starch content in the complex increased from 10.38% to 35.12%, while the rapidly digestible starch (RDS) content decreased from 72.77% to 40.62%. Collectively, these findings underscore the immense potential of VGS as a carrier for the transport of sensitive actives.

Crosslinking by Click Chemistry of Hyaluronan Graft Copolymers Involving Resorcinol-Based Cinnamate Derivatives Leading to Gel-like Materials.

The well-known "click chemistry" reaction copper(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) was used to transform under very mild conditions hyaluronan-based graft copolymers HA(270)-FA-Pg into the crosslinked derivatives HA(270)-FA-TEGERA-CL and HA(270)-FA-HEGERA-CL. In particular, medium molecular weight (i.e., 270 kDa) hyaluronic acid (HA) grafted at various extents (i.e., 10, 20, and 40%) with fluorogenic ferulic acid (FA) residue bonding propargyl groups were used in the CuAAC reaction with novel azido-terminated crosslinking agents Tri(Ethylene Glycol) Ethyl Resorcinol Acrylate (TEGERA) and Hexa(Ethylene Glycol) Ethyl Resorcinol Acrylate (HEGERA). The resulting HA(270)-FA-TEGERA-CL and HA(270)-FA-HEGERA-CL materials were characterized from the point of view of their structure by performing NMR studies. Moreover, the swelling behavior and rheological features were assessed employing TGA and DSC analysis to evaluate the potential gel-like properties of the resulting crosslinked materials. Despite the 3D crosslinked structure, HA(270)-FA-TEGERA-CL and HA(270)-FA-HEGERA-CL frameworks showed adequate swelling performance, the required shear thinning behavior, and coefficient of friction values close to those of the main commercial HA solutions used as viscosupplements (i.e., 0.20 at 10 mm/s). Furthermore, the presence of a crosslinked structure guaranteed a longer residence time. Indeed, HA(270)-FA-TEGERA-CL-40 and HA(270)-FA-HEGERA-CL-40 after 48 h showed a four times greater enzymatic resistance than the commercial viscosupplements. Based on the promising obtained results, the crosslinked materials are proposed for their potential applicability as novel viscosupplements.

Bacteria carrying mobile colistin resistance genes and their control measures, an updated review.

The plasmid encoded mobile colistin resistance (MCRs) enzyme poses a significant challenge to the clinical efficacy of colistin, which is frequently employed as a last resort antibiotic for treating infections caused by multidrug resistant bacteria. This transferase catalyzes the addition of positively charged phosphoethanolamine to lipid A of the outer membrane of gram-negative bacteria, thereby facilitating the acquired colistin resistance. This review aims to summarize and critically discuss recent advancements in the distribution and pathogenesis of mcr-positive bacteria, as well as the various control measures available for treating these infections. In addition, the ecology of mcr genes, colistin-resistance mechanism, co-existence with other antibiotic resistant genes, and their impact on clinical treatment are also analyzed to address the colistin resistance crisis. These insights provide a comprehensive perspective on MCRs and serve as a valuable reference for future therapeutic approaches to effectively combat mcr-positive bacterial infections.

Novel hydrothermal modification to alter functionality and reduce glycemic response of pea starch

Despite being an effective and clean-label method, heat-moisture treatment (HMT) is not commonly used for starch modification in industry due to the difficulty of scale-up. This study aimed to develop a novel method of using extrusion combined with high-temperature drying (EHTD) as an alternative to HMT for starch modification. Pea starch was subjected to extrusion at 37.5 % moisture level and with a low-temperature profile (≤ 65 °C), followed by immediate heating at 130 °C for 1 h. EHTD significantly damaged the granules, altered the X-ray diffraction pattern, and reduced the relative crystallinity of pea starch. Overall, EHTD-modified pea starch exhibited increased gelatinization temperatures and decreased gelatinization enthalpy change, lowered pasting viscosity and gel hardness, as well as enhanced enzymatic resistance than the native pea starch. More importantly, in a human feeding trial (n = 20 healthy participants) to monitor plasma glucose response over a period of 2 h after consuming water-boiled sample (35 g starch, dry basis), EHTD-modified pea starch exhibited 22 % reduction (p < 0.01) in plasma glucose incremental area under the curve as compared to the native counterpart. The results indicated that EHTD could be a new simple and clean-label method to produce functional and low-glycemic starch ingredients.

Hydrophobic interaction-induced self-assembly of V-type lotus starch with butyric acid into stable structures: Regulation by butyric acid concentration

V-amylose is a modified helical structure capable of interacting with butyric acid (BA), which typically shows limited affinity for native amylose. The encapsulation of BA within V-amylose enhances its enzymatic resistance while facilitating the delivery of BA to the gut, where it can exert beneficial health effects. Consequently, enhancing the incorporation of BA into starch-based food is a crucial strategy for achieving these objectives. The concentration of guest BA plays a critical role in the hydrophobic interaction-induced complexation with V-amylose, and understanding the structural changes involved in this process is essential for the design of optimal products. In this study, V-amylose derived from high-amylose lotus starch was utilized to form complexes with BA. The structure and in vitro digestibility of the complexes formed at varying BA concentrations were investigated. The results demonstrate that higher BA concentrations weakened the hydrophobic interactions in the V-amylose system. Nevertheless, the highest complex index (i.e., 11.7 g/100 g) of V-amylose was attained at a 50 % BA concentration, indicating a balance between BA-regulated hydrophobic aggregation and the density of BA during complexation. These V-amylose complexes produced with elevated BA content exhibited high crystallinity and molecular order, along with enhanced thermal stability and resistance to enzymolysis. These findings support the feasibility of loading BA into V-amylose and provide valuable insights into the hydrophobic complexation regulated by BA concentration.

Fluorogenic RNA aptamer based artificial membraneless organelles for small molecule and cell sensing

Artificial membraneless organelle with molecularly crowded and confined microenvironment shows great potential for improving functional RNA properties and developing biosensing. However, the performance of current artificial membraneless organelles is impaired with polycationic components. In this work, we demonstrate the construction of a purely fluorescent RNA aptamer based artificial membraneless organelle (FRAME) for improving RNA performance and biosensing. The fluorescent RNA aptamer in FRAME exhibited higher enzymatic resistance, thermostability, photostability and binding affinity than that dispersed in solution. The FRAME can be easily designed as a biosensor for tetracycline detection in lake water and tap water, which eliminated the adverse effects of polycationic components and demonstrated about 42.8-fold sensitivity improvement than the biosensor prepared with Poly-L-Lysine and RNA. By introducing epithelial cell adhesion molecule (EpCAM) aptamer to specific recognition of tumor cells, the FRAME is easily engineered as an ultra-sensitive probe to precisely identify cancer cell phenotypes. We believe that the proposed FRAME system would provide a universal platform for biosensing.

The evolution of granular surface structure and functional properties in rice starch during grain filling

The developmental changes in the granular surface structure and functional properties of starch during the entire grain filling period of rice (around 40 days) were investigated. The specific surface area of rice starch significantly decreased firstly then stabilized during growth due to increasing granular size. The pore volume decreased from 5.40 cm3/g at 6th day after anthesis (DAA-6) to 3.02 cm3/g (DAA-46). More starch granule-associated proteins (SGAPs) accumulated on the surface and in channels. Swelling power decreased by 46 %, whereas the flow behavior index (n) decreased by 32 % in upward curve during starch development from DAA-6 to DAA-30. Tan δ first dropped then remained steady at DAA 22–34 and lightly rebounded at the final stage, indicating that starch in the middle stage tended to have greater viscoelastic gel behavior at all sweeps. Mature starch showed lower in vitro hydrolysis rate and exhibited stronger enzymatic resistance. The results showed that granular surface features of rice starch may be an essential factor in determining rheological behavior and resistance to hydrolysis.

The contribution of porins to enterobacterial drug resistance.

In Enterobacteriaceae, susceptibility to cephalosporins and carbapenems is often associated with membrane and enzymatic barrier resistance. For about 20 years, a large number of Klebsiella pneumoniae, Escherichia coli and Enterobacter cloacae presenting ß-lactam resistance have been isolated from medical clinics. In addition, some of the resistant isolates exhibited alterations in the outer membrane porin OmpC-OmpF orthologues, resulting in the complete absence of gene expression, replacement by another porin or mutations affecting channel properties. Interestingly, for mutations reported in OmpC-OmpF orthologues, major changes in pore function were found to be present in the gene encoding for OmpC. The alterations were located in the constriction region of the porin and the resulting amino acid substitutions were found to induce severe restriction of the lumen diameter and/or alteration of the electrostatic field that governs the diffusion of charged molecules. This functional adaptation through porins maintains the entry of solutes necessary for bacterial growth but critically controls the influx of harmful molecules such as β-lactams at a reduced cost. The data recently published show the importance of understanding the underlying parameters affecting the uptake of antibiotics by infectious bacteria. Furthermore, the development of reliable methods to measure the concentration of antibiotics within bacterial cells is key to combat impermeability-resistance mechanisms.