Lipidated DNA Nanostructures Target and Rupture Bacterial Membranes.

Chemistry has the power to endow supramolecular nanostructures with new biomedically relevant functions. Here it is reported that DNA nanostructures modified with cholesterol tags disrupt bacterial membranes to cause microbial cell death. The lipidated DNA nanostructures bind more readily to cholesterol-free bacterial membranes than to cholesterol-rich, eukaryotic membranes. These highly negatively charged, lipidated DNA nanostructures cause bacterial cell death by rupturing membranes. Strikingly, killing is mediated by clusters of barrel-shaped nanostructures that adhere to the membrane without the involvement of expected bilayer-puncturing barrels. These DNA nanomaterials may inspire the development of polymeric or small-molecule antibacterial agents that mimic the principles of selective binding and rupturing to help combat antimicrobial resistance.

Bacterial killing by complement requires membrane attack complex formation via surface-bound C5 convertases.

The immune system kills bacteria by the formation of lytic membrane attack complexes (MACs), triggered when complement enzymes cleave C5. At present, it is not understood how the MAC perturbs the composite cell envelope of Gram-negative bacteria. Here, we show that the role of C5 convertase enzymes in MAC assembly extends beyond the cleavage of C5 into the MAC precursor C5b. Although purified MAC complexes generated from preassembled C5b6 perforate artificial lipid membranes and mammalian cells, these components lack bactericidal activity. In order to permeabilize both the bacterial outer and inner membrane and thus kill a bacterium, MACs need to be assembled locally by the C5 convertase enzymes. Our data indicate that C5b6 rapidly loses the capacity to form bactericidal pores; therefore, bacterial killing requires both in situ conversion of C5 and immediate insertion of C5b67 into the membrane. Using flow cytometry and atomic force microscopy, we show that local assembly of C5b6 at the bacterial surface is required for the efficient insertion of MAC pores into bacterial membranes. These studies provide basic molecular insights into MAC assembly and bacterial killing by the immune system.

Imaging the Effects of Peptide Materials on Phospholipid Membranes by Atomic Force Microscopy.

Recent advances in biomolecular design require accurate measurements performed in native or near-native environments in real time. Atomic force microscopy (AFM) is a powerful tool to observe the dynamics of biologically relevant processes at aqueous interfaces with high spatial resolution. Here, we describe imaging protocols to characterize the effects of peptide materials on phospholipid membranes in solution by AFM. These protocols can be used to determine the mechanism and kinetics of membrane-associated activities at the nanoscale.

Cantilever Sensors for Rapid Optical Antimicrobial Sensitivity Testing.

Growing antimicrobial resistance (AMR) is a serious global threat to human health. Current methods to detect resistance include phenotypic antibiotic sensitivity testing (AST), which measures bacterial growth and is therefore hampered by a slow time to obtain results (∼12-24 h). Therefore, new rapid phenotypic methods for AST are urgently needed. Nanomechanical cantilever sensors have recently shown promise for rapid AST but challenges of bacterial immobilization can lead to variable results. Herein, a novel cantilever-based method is described for detecting phenotypic antibiotic resistance within ∼45 min, capable of detecting single bacteria. This method does not require complex, variable bacterial immobilization and instead uses a laser and detector system to detect single bacterial cells in media as they pass through the laser focus. This provides a simple readout of bacterial antibiotic resistance by detecting growth (resistant) or death (sensitive), much faster than the current methods. The potential of this technique is demonstrated by determining the resistance in both laboratory and clinical strains of Escherichia coli (E. coli), a key species responsible for clinically burdensome urinary tract infections. This work provides the basis for a simple and fast diagnostic tool to detect antibiotic resistance in bacteria, reducing the health and economic burdens of AMR.

Engineering monolayer poration for rapid exfoliation of microbial membranes.

The spread of bacterial resistance to traditional antibiotics continues to stimulate the search for alternative antimicrobial strategies. All forms of life, from bacteria to humans, are postulated to rely on a fundamental host defense mechanism, which exploits the formation of open pores in microbial phospholipid bilayers. Here we predict that transmembrane poration is not necessary for antimicrobial activity and reveal a distinct poration mechanism that targets the outer leaflet of phospholipid bilayers. Using a combination of molecular-scale and real-time imaging, spectroscopy and spectrometry approaches, we introduce a structural motif with a universal insertion mode in reconstituted membranes and live bacteria. We demonstrate that this motif rapidly assembles into monolayer pits that coalesce during progressive membrane exfoliation, leading to bacterial cell death within minutes. The findings offer a new physical basis for designing effective antibiotics.

Estrategia para la formación de valores en estudiantes de tecnología de la salud / Intervention strategy for women at risk of preterm delivery

Se elabora una estrategia sobre el trabajo con los valores, para dar respuesta a la urgente formación masiva de profesionales de ciencias médicas, especialmente, de carreras de Tecnología de la Salud, para de esta forma elevar la eficiencia en su formación y que trascienda a la excelencia en los servicios que prestan. Se utilizan diferentes métodos de nivel teórico: análisis y síntesis, histórico-lógico, sistémico-estructural, así como análisis documental. El sistema de actividades propuesto se sustenta en las ideas rectoras de la formación de valores. El aporte del trabajo se precisa a partir de los contextos significativos para el estudiantado (escuela-familia-comunidad) mediante un sistema de actividades contribuyentes al fortalecimiento de valores(AU)

A strategy on working with values is developed, for responding to the urgent mass training of health science professionals , especially Health Technology career, to thus increase the efficiency of their training and that transcends the excellence in the services they provide . Using different theoretical methods : analysis and synthesis , historical, logical , systemic , structural and documentary analysis. The system proposed work is based on the guiding principles of values . The labor input is required from the meaningful context for students ( school-family-community) through a system of activities contributing to the strengthening of values