Enterobactin-Mediated Delivery of β-Lactam Antibiotics Enhances Antibacterial Activity against Pathogenic Escherichia coli

The design, synthesis, and characterization of enterobactin–antibiotic conjugates, hereafter Ent-Amp/Amx, where the β-lactam antibiotics ampicillin (Amp) and amoxicillin (Amx) are linked to a monofunctionalized enterobactin scaffold via a stable poly(ethylene glycol) linker are reported. Under conditions of iron limitation, these siderophore-modified antibiotics provide enhanced antibacterial activity against Escherichia coli strains, including uropathogenic E. coli CFT073 and UTI89, enterohemorrhagic E. coli O157:H7, and enterotoxigenic E. coli O78:H11, compared to the parent β-lactams. Studies with E. coli K-12 derivatives defective in ferric enterobactin transport reveal that the enhanced antibacterial activity observed for this strain requires the outer membrane ferric enterobactin transporter FepA. A remarkable 1000-fold decrease in minimum inhibitory concentration (MIC) value is observed for uropathogenic E. coli CFT073 relative to Amp/Amx, and time-kill kinetic studies demonstrate that Ent-Amp/Amx kill this strain more rapidly at 10-fold lower concentrations than the parent antibiotics. Moreover, Ent-Amp and Ent-Amx selectively kill E. coli CFT073 co-cultured with other bacterial species such as Staphylococcus aureus, and Ent-Amp exhibits low cytotoxicity against human T84 intestinal cells in both the apo and iron-bound forms. These studies demonstrate that the native enterobactin platform provides a means to effectively deliver antibacterial cargo across the outer membrane permeability barrier of Gram-negative pathogens utilizing enterobactin for iron acquisition.Pacific Southwest Regional Center of Excellence for Biodefense and Emerging Infectious DiseaseKinship Foundation. Searle Scholars ProgramMassachusetts Institute of Technology. Department of Chemistr

Preparation and characterization of oleogel emulsions: A comparative study between the use of recovered and commercial sunflower waxes as structuring agent

The objective of this study was to evaluate the capacity of recovered sunflower waxes (RW) to be used as a structuring agent of oleogel emulsions in comparison with commercial sunflower waxes (CW). RW were recovered from filter cake with a simple hexane extraction procedure. For this purpose, oleogel-based emulsions were prepared using 2%, 3.5%, and 5% w/w wax in oleogel and characterized using several physicochemical techniques in order to evaluate the potential of these materials to develop products with functionality similar to commercial margarines. The total wax esters content of RW was similar to that of the CW and was mainly composed of wax esters with more than 44 carbon atoms (crystallizable waxes). Polarized light and scanning electron microscopy showed that RW produced emulsions with more intricate crystalline networks composed of smaller platelets than CW. The melting enthalpy was greater in CW emulsions than RW emulsions, which was in agreement with the thermal behavior found for CW and RW. The oil binding capacity of CW oleogel emulsions was higher than the RW ones, and this property improved with the increase in wax concentration. Likewise, the elastic behavior, as well as hardness and adhesiveness, increased with the wax content as a result of a greater amount of microstructural elements composing the network of these semisolid materials. The oleogel emulsions stability was monitored for 2 months at room temperature. The increase of CW concentration slowed down the coalescence process, but this behavior was not observed for RW emulsions. Obtained results demonstrated that RW oleogel emulsions have the potential to replace the functionality of soft spreadable products. Practical Application: Wax esters are organogelators that have been shown to successfully gel liquid oil at low concentrations. In this work, we are interested in evaluating the potential of sunflower waxes recovered from filter cake, a waste generated during refined oil production, to structure oil and produce oil-in-water emulsions with functionality similar to commercial margarines. With this, it is sought not only the development of healthier fats but also the use of wastes to generate more sustainable products.Fil: Merchan Sandoval, Julie Pauline. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; ArgentinaFil: Carelli Albarracin, Amalia Antonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; ArgentinaFil: Palla, Camila Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; ArgentinaFil: Baumler, Erica Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; Argentin

Absence of PmrAB-Mediated Phosphoethanolamine Modifications of Citrobacter rodentium Lipopolysaccharide Affects Outer Membrane Integrity▿†

The PmrAB two-component system of enterobacteria regulates a number of genes whose protein products modify lipopolysaccharide (LPS). The LPS is modified during transport to the bacterial outer membrane (OM). A subset of PmrAB-mediated LPS modifications consists of the addition of phosphoethanolamine (pEtN) to lipid A by PmrC and to the core by CptA. In Salmonella enterica, pEtN modifications have been associated with resistance to polymyxin B and to excess iron. To investigate putative functions of pEtN modifications in Citrobacter rodentium, ΔpmrAB, ΔpmrC, ΔcptA, and ΔpmrC ΔcptA deletion mutants were constructed. Compared to the wild type, most mutant strains were found to be more susceptible to antibiotics that must diffuse across the LPS layer of the OM. All mutant strains also showed increased influx rates of ethidium dye across their OM, suggesting that PmrAB-regulated pEtN modifications affect OM permeability. This was confirmed by increased partitioning of the fluorescent dye 1-N-phenylnaphthylamine (NPN) into the OM phospholipid layer of the mutant strains. In addition, substantial release of periplasmic β-lactamase was observed for the ΔpmrAB and ΔpmrC ΔcptA strains, indicating a loss of OM integrity. This study attributes a new role for PmrAB-mediated pEtN LPS modifications in the maintenance of C. rodentium OM integrity