RESUMO
This study aims to explore the antimicrobial activity of rifampicin (RIF) and ascorbic acid (ASC) co-loaded into alginate (ALG)/chitosan (CS) nanoparticles (RIF/ASC NPs) and tested for their antibacterial activity against several strains of methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). Also, the present research focused on exploring the possible antibacterial mechanism of action of these RIF/ASC NPs, which demonstrated a significant biocide activity against the S. aureus strains with minimum inhibitory concentrations (MIC) between 2- and 8-fold lower than those one exhibited with the free antibiotic RIF. The proposed antimicrobial mechanism of action of the RIF/ASC NPs seems to be the result of collaborative effects between NPs and the RIF/ASC antibiotic combination. Moreover, results indicated that the functionalized RIF/ASC NP surface played a crucial role on the processes of NP adhesion into the bacterial surface, the alterations on the cell membrane integrity, and the cell uptake of the RIF/ASC antibiotic into bacteria. Further, the in vivo lung deposition pattern of empty NPs labeled (NPs-FITC) with isothiocyanate fluorescein in rats was investigated post intratracheal instillation of NPs. In summary, findings from this work show that our novel designed engineered RIF/ASC co-loaded NPs could be a suitable system for antibiotic lung administration with promising perspectives for effective treatments of pulmonary intracellular infections for those known antibiotics that are losing effectiveness due to antimicrobial resistance problems. Graphical Abstract.
Assuntos
Antibacterianos/administração & dosagem , Quitosana , Staphylococcus aureus Resistente à Meticilina , Nanopartículas , Rifampina/administração & dosagem , Alginatos , Animais , Antibacterianos/farmacologia , Pulmão , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Ratos , Rifampina/farmacologia , Staphylococcus aureus/efeitos dos fármacosRESUMO
Oxidative stress is a condition caused by the high intracellular concentrations of reactive oxygen species (ROS) that includes superoxide anion radicals, hydroxyl radicals and hydrogen peroxide. Nanoparticles could cause rapid generation of free radicals by redox reactions. ROS can react directly with membrane lipids, proteins and DNA and are normally scavenged by antioxidants that are capable of neutralizing; however, elevated concentrations of ROS in bacterial cells can result in oxidative stress. The aim of this work was contribute to the knowledge of action mechanism of silver nanoparticles (Ag-NPs) and their relation to the generation of oxidative stress in bacteria. We demonstrated that Ag-NPs generated oxidative stress in Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa mediated by the increment of ROS and this increase correlated with a better antimicrobial activity. On the other hand, we showed that the oxidative stress caused by the Ag-NPs biosynthesized was associated to a variation in the level of reactive nitrogen intermediates (RNI). Oxidative stress in bacteria can result from disruption of the electronic transport chain due to the high affinity of Ag-NPs for the cell membrane. This imbalance in the oxidative stress was evidentiated by a macromolecular oxidation at level of DNA, lipids and proteins in E. coli exposed to Ag-NPs. The formation of ROS and RNI by Ag-NPs may also be considered to explain the bacterial death.
Assuntos
Antibacterianos/toxicidade , Escherichia coli/efeitos dos fármacos , Nanopartículas Metálicas/toxicidade , Pseudomonas aeruginosa/efeitos dos fármacos , Prata/toxicidade , Staphylococcus aureus/efeitos dos fármacos , DNA Bacteriano/metabolismo , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Pseudomonas aeruginosa/crescimento & desenvolvimento , Pseudomonas aeruginosa/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Staphylococcus aureus/crescimento & desenvolvimento , Staphylococcus aureus/metabolismoRESUMO
Photosensitizing anthraquinones isolated from Heterophyllaea pustulata Hook f. (Rubiaceae), namely soranjidiol, rubiadin, damnacanthal and 5,5'-bisoranjidiol, showed antibacterial activity (bacteriostatic/bactericide) on Staphylococcus aureus. The mechanism of action seems to involve an increase in the levels of superoxide anion (O(2)(·-)) and/or singlet molecular oxygen ((1)O(2)). Moreover, the effect of actinic irradiation as a boosting agent for the production of both reactive species of oxygen as well as its influence on antibacterial activity was assessed. The routine susceptibility assay (minimum inhibitory concentration determination) was carried out by means of the broth macrodilution method. Bactericide activity was determined counting the colony-forming units per milliliter (cfu/mL) in plate. The O(2)(·-) production was determined by means of an indirect photobiological assay (Nitroblue Tetrazolium test), and the production of (1)O(2) was followed using an indirect steady-state method, with methionine as the (1)O(2) chemical quencher.
Assuntos
Antraquinonas/química , Antibacterianos/química , Fármacos Fotossensibilizantes/química , Rubiaceae/química , Antraquinonas/isolamento & purificação , Antraquinonas/farmacologia , Antibacterianos/isolamento & purificação , Antibacterianos/farmacologia , Testes de Sensibilidade Microbiana , Fármacos Fotossensibilizantes/isolamento & purificação , Fármacos Fotossensibilizantes/farmacologia , Oxigênio Singlete/metabolismo , Staphylococcus aureus/efeitos dos fármacos , Superóxidos/metabolismoRESUMO
Shiga toxin (Stx) and hemolysin (Hly) of Escherichia coli O157:H7 produced an increase of reactive oxygen species (ROS) in normal human blood. In vitro assays showed that stimuli of ROS with these toxins oxidized proteins to carbonyls in plasma and raised the degradation of oxidized macromolecules, with the AOPP/carbonyl relationship also increasing. The oxidative stress generated by toxins during the Hemolytic Uremic Syndrome (HUS) produced oxidation of blood proteins with a rise in advanced oxidation protein products (AOPP) in children with HUS. There was a response from the antioxidant system in these patients, evaluated through the determination of the total antioxidant capacity of plasma by the Ferric Reducing Antioxidant Power (FRAP), which reduced the stimuli of ROS during in vitro incubation with Stx or Hly. The application of natural antioxidants was sufficient to reduce in vitro the oxidative stress provoked by both toxins in blood.