ABSTRACT
Many archetypal and emerging classes of small-molecule therapeutics form covalent protein adducts. In vivo, both the resulting conjugates and their off-target side-conjugates have the potential to elicit antibodies, with implications for allergy and drug sequestration. Although ß-lactam antibiotics are a drug class long associated with these immunological phenomena, the molecular underpinnings of off-target drug-protein conjugation and consequent drug-specific immune responses remain incomplete. Here, using the classical ß-lactam penicillin G (PenG), we probe the B and T cell determinants of drug-specific IgG responses to such conjugates in mice. Deep B cell clonotyping reveals a dominant murine clonal antibody class encompassing phylogenetically-related IGHV1, IGHV5 and IGHV10 subgroup gene segments. Protein NMR and x-ray structural analyses reveal that these drive structurally convergent binding modes in adduct-specific antibody clones. Their common primary recognition mechanisms of the penicillin side-chain moiety (phenylacetamide in PenG)-regardless of CDRH3 length-limits cross-reactivity against other ß-lactam antibiotics. This immunogenetics-guided discovery of the limited binding solutions available to antibodies against side products of an archetypal covalent inhibitor now suggests future potential strategies for the 'germline-guided reverse engineering' of such drugs away from unwanted immune responses.
Subject(s)
Anti-Bacterial Agents , Animals , Mice , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/immunology , Immunoglobulin G/immunology , Penicillin G/immunology , Penicillin G/chemistry , B-Lymphocytes/immunology , Penicillins/immunology , Penicillins/chemistry , Female , Cross Reactions/immunology , Crystallography, X-RayABSTRACT
A multifunctional surface-enhanced Raman scattering (SERS) platform integrating sensitive detection and drug resistance analysis was developed for Gram-positive bacteria. The substrate was based on self-assembled Ti3C2Tx@Au NPs films and capture molecule phytic acid (IP6) to achieve specific capture of Gram-positive bacteria and different bacteria were analyzed by fingerprint signal. It had advantages of good stability and homogeneity (RSD = 8.88%). The detection limit (LOD) was 102 CFU/mL for Staphylococcus aureus and 103 CFU/mL for MRSA, respectively. A sandwich structure was formed on the capture substrate by signal labels prepared by antibiotics (penicillin G and vancomycin) and non-interference SERS probe molecules (4-mercaptobenzonitrile (2223 cm-1) and 2-amino-4-cyanopyridine (2240 cm-1)) to improve sensitivity. The LOD of Au NPs@4-MBN@PG to S. aureus and Au NPs@AMCP@Van to MRSA and S. aureus were all improved to 10 CFU/mL, with a wide dynamic linear range from 108 to 10 CFU/mL (R2 ≥ 0.992). The SERS platform can analyze the drug resistance of drug-resistant bacteria. Au NPs@4-MBN@PG was added to the substrate and captured MRSA to compare the SERS spectra of 4-MBN. The intensity inhomogeneity of 4-MBN at the same concentrations of MRSA and the nonlinearity at the different concentrations of MRSA revealed that MRSA was resistant to PG. Finally, the SERS platform achieved the determination of MRSA in blood. Therefore, this SERS platform has great significance for the determination and analysis of Gram-positive bacteria.
Subject(s)
Anti-Bacterial Agents , Gold , Limit of Detection , Metal Nanoparticles , Spectrum Analysis, Raman , Staphylococcus aureus , Titanium , Spectrum Analysis, Raman/methods , Gold/chemistry , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/chemistry , Titanium/chemistry , Metal Nanoparticles/chemistry , Staphylococcus aureus/drug effects , Staphylococcus aureus/isolation & purification , Methicillin-Resistant Staphylococcus aureus/drug effects , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Vancomycin/pharmacology , Vancomycin/chemistry , Drug Resistance, Bacterial , Microbial Sensitivity Tests , Penicillin G/pharmacology , Penicillin G/chemistry , Gram-Positive Bacteria/drug effects , Gram-Positive Bacteria/isolation & purificationABSTRACT
Understanding the functional role of protein-excited states has important implications in protein design and drug discovery. However, because these states are difficult to find and study, it is still unclear if excited states simply result from thermal fluctuations and generally detract from function or if these states can actually enhance protein function. To investigate this question, we consider excited states in ß-lactamases and particularly a subset of states containing a cryptic pocket which forms under the Ω-loop. Given the known importance of the Ω-loop and the presence of this pocket in at least two homologs, we hypothesized that these excited states enhance enzyme activity. Using thiol-labeling assays to probe Ω-loop pocket dynamics and kinetic assays to probe activity, we find that while this pocket is not completely conserved across ß-lactamase homologs, those with the Ω-loop pocket have a higher activity against the substrate benzylpenicillin. We also find that this is true for TEM ß-lactamase variants with greater open Ω-loop pocket populations. We further investigate the open population using a combination of NMR chemical exchange saturation transfer experiments and molecular dynamics simulations. To test our understanding of the Ω-loop pocket's functional role, we designed mutations to enhance/suppress pocket opening and observed that benzylpenicillin activity is proportional to the probability of pocket opening in our designed variants. The work described here suggests that excited states containing cryptic pockets can be advantageous for function and may be favored by natural selection, increasing the potential utility of such cryptic pockets as drug targets.
Subject(s)
Penicillinase/chemistry , Penicillinase/drug effects , beta-Lactamases/chemistry , beta-Lactamases/pharmacology , Binding Sites , Escherichia coli , Escherichia coli Proteins , Molecular Dynamics Simulation , Mutation , Penicillin G/chemistry , Penicillin G/metabolism , Penicillinase/metabolism , Protein Conformation , Proteins/chemistry , Proteins/genetics , Proteins/metabolism , beta-Lactamases/geneticsABSTRACT
Penicillium chrysogenum, recently re-identified as Penicillium rubens, is the microorganism used for the industrial production of penicillin. This filamentous fungus (mold) probably represents the best example of adaptation of a microorganism to industrial production conditions and therefore, it can be considered as a model organism for the study of primary and secondary metabolism under a highly stressful environment. In this regard, biosynthesis and production of benzylpenicillin can be used as an interesting phenotypic trait for those studies. In this chapter, we describe P. chrysogenum culture procedures for the production of benzylpenicillin and the process of antibiotic quantitation either by bioassay or by high-performance liquid chromatography (HPLC).
Subject(s)
Fermentation/physiology , Penicillin G/chemistry , Penicillin G/metabolism , Penicillium chrysogenum/metabolism , Penicillium chrysogenum/physiology , Biological Assay/methods , Chromatography, High Pressure Liquid/methods , Secondary Metabolism/physiologyABSTRACT
We present a sensitive and rapid screening method for the determination of ß-lactamase activity of antibiotic-resistant bacteria, by designing a pH-sensitive fluorescent dye-doped mesoporous silica nanoparticle encapsulated with penicillin G as a substrate. When penicillin G was hydrolysed by ß-lactamase and converted into penicilloic acid, the acidic environment resulted in fluorescence quenching of the dye. The dye-doped mesoporous nanoparticles not only enhanced the ß-lactamase-catalyzed reaction rate but also stablized the substrate, penicillin G, which degrades into penicilloic acid in a water solution without ß-lactamase. Twentyfive clinical bacterial samples were tested and the antibiotic resistant and susceptible strains were identified. The proposed method may detect the presence of ß -lactamases of clinically relevant samples in less than 1â hour. Moreover, the detection limit of ß-lactamase activity was as low as 7.8×10-4â U/mL, which was determined within two hours.
Subject(s)
Enzyme Assays/methods , Fluorescent Dyes/chemistry , Nanoparticles/chemistry , beta-Lactamases/metabolism , Biocatalysis , Kinetics , Penicillin G/chemistry , Porosity , Time Factors , Water/chemistry , beta-Lactamases/chemistryABSTRACT
A simplistic approach is presented for the synthesis of ultrasonically fabricated graphene oxide functionalized with polyaniline and N-[3-(Trimethoxysilyl)propyl]ethylenediamine. The synthesized nanocomposite was then employed for the facile, green, ultrasound-assisted, magnetic dispersive solid-phase extraction of amoxicillin, ampicillin, and penicillin G in milk samples and infant formula prior to high-performance liquid chromatography-ultraviolet determination. The designed nanocomposites were comprehensively characterized using field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. In order to achieve the best extraction efficiencies, the influential parameters including pH, amount of magnetic sorbent, type and volume of elution solvent, extraction time, sample volume, and desorption time were assessed. At the optimum conditions, linear ranges of 2.5-1000 (µg L-1) for ampicillin and penicillin G and a linear range of 2.5-750 (µg L-1) were obtained for amoxicillin at optimum conditions. Moreover, the limits of detection (S/N = 3) of 0.5, 0.8, and 0.9 (µg L-1) were obtained for amoxicillin, ampicillin, and penicillin G, respectively. The precision (relative standard deviations (%)) values of 3.1, 2.6, and 2.5 at the concentration of 50 µg L-1 for seven replicates were obtained for ampicillin, amoxicillin, and penicillin G, respectively. The efficiencies of ≤ 96% and relative standard deviations of less than 3.1% were also obtained thereby confirming the high potential of the synthesized nanocomposites for simultaneous preconcentration and separation of the ß-lactam antibiotics in complex matrixes. Graphical Abstract.
Subject(s)
Amoxicillin/chemistry , Ampicillin/chemistry , Graphite/chemical synthesis , Penicillin G/chemistry , Solid Phase Extraction/methods , Ultrasonics/methods , Animals , Anti-Bacterial Agents/chemistry , Biosensing Techniques , Cattle , Drug Residues/chemistry , Food Analysis , Food Contamination , Magnetics , Milk/chemistry , Molecular Structure , Nanocomposites/chemistry , Water Pollutants, Chemical/chemistryABSTRACT
The synthesis of structurally new haptens and the development of suitable antigens are essential for boosting the sensitivity of drug allergy diagnostic testing. Unprecedented structural antigens for benzylpenicillin and amoxicillin are characterised and evaluated in a cohort of 70 subjects with a turnkey solution based on consumer electronics.
Subject(s)
Diagnostic Tests, Routine/methods , Drug Hypersensitivity/metabolism , Haptens/chemistry , Lactams/metabolism , beta-Lactams/chemistry , Adult , Aged , Aged, 80 and over , Amoxicillin/chemistry , Anti-Bacterial Agents/chemistry , Aztreonam/chemistry , Carbonates/chemistry , Cohort Studies , Diamines/chemistry , Female , Humans , Male , Middle Aged , Penicillin G/chemistry , Serum Albumin, Human/chemistry , Structure-Activity Relationship , Substrate SpecificityABSTRACT
A rapid determination method of residual penicillin G and its two metabolites in citrus was developed and validated by dispersive solid-phase extraction and ultra-high performance liquid chromatography-tandem mass spectrometry (DSPE/UPLC-MS/MS). The samples were extracted with 80% acetonitrile and purified with octadecylsilane. High linearity was obtained with correlation coefficients (r2 ) >0.9981. The limits of quantification were 0.005-0.01 mg/kg. The recoveries of penicillin G and its metabolites spiked in blank citrus were within 76.7-107%, with relative standard deviations of 1.3-9.6%. The dissipation dynamics and distribution of penicillin G in citrus followed first-order kinetics, with half-life of 1.7-2.7 days. Penicillin G degraded easily in citrus and the metabolite was mainly penilloic acid, which can exist stably for long time. The terminal residues of penicillin G in pulp, whole citrus and peels were 0.015-0.701, 0.047-7.653 and 0.162-13.376 mg/kg, respectively. The hazard indexes for risk assessment of citrus were significantly <1, suggesting that the health risks to humans after consumption of citrus were insignificant and negligible. These results could provide necessary data for evaluating the safe and proper use of penicillin G in citrus.
Subject(s)
Agrochemicals/analysis , Citrus/chemistry , Fruit/chemistry , Penicillin G/analysis , Pesticide Residues/analysis , Agrochemicals/chemistry , Agrochemicals/isolation & purification , Chromatography, High Pressure Liquid/methods , Limit of Detection , Linear Models , Penicillin G/analogs & derivatives , Penicillin G/chemistry , Penicillin G/isolation & purification , Pesticide Residues/chemistry , Pesticide Residues/isolation & purification , Reproducibility of Results , Risk Assessment , Solid Phase Extraction , Tandem Mass Spectrometry/methodsABSTRACT
The dramatic increase in bacterial resistance over the past three decades has greatly reduced the effectiveness of nearly all clinical antibiotics, bringing infectious disease to the forefront as a dire threat to global health. To combat these infections, adjuvant therapies have emerged as a way to reactivate known antibiotics against resistant pathogens. Herein, we report the evaluation of simplified α-pyrone adjuvants capable of potentiating penicillin G against Pseudomonas aeruginosa, a Gram-negative pathogen whose multidrug-resistant strains have been labeled by the Centers for Disease Control and Prevention as a serious threat to public health.
Subject(s)
Anti-Bacterial Agents/pharmacology , Penicillin G/pharmacology , Pseudomonas aeruginosa/drug effects , Pyrones/pharmacology , Anti-Bacterial Agents/chemistry , Dose-Response Relationship, Drug , Microbial Sensitivity Tests , Molecular Structure , Penicillin G/chemistry , Pyrones/chemistry , Structure-Activity RelationshipABSTRACT
We aimed to develop a molecularly imprinted polymeric systems with using penicillin G as a template molecule for removal of the antibiotic residues from environmental samples. Firstly, Pen-G-imprinted poly (2-hydroxyethyl methacrylate-N-methacryloyl-L-alanine) [p(HEMA-MAAL)] nanopolymers were synthesized by surfactant-free emulsion polymerization method. Then, template molecule (Pen-G) was extracted from nanopolymers. Synthesized nanopolymers were characterized by different methods such as Fourier-transform infrared spectroscopy (FTIR), elemental and zeta-size analysis, scanning electron microscope (SEM), and surface area calculations. Nanopolymers have 60.38 nm average size and 1034.22 m2/g specific surface area. System parameters on Pen-G adsorption onto Pen-G imprint nanopolymers were investigated at different conditions. The specific adsorption value (Qmax) of molecularly impirinted p(HEMA-MAAL) nanopolymers was found 71.91 g/g for Pen-G in 5 mg/mL Pen-G initial concentration. Pen-G adsorption of molecularly imprinted nanopolymers was 15 times more than non-imprinted polymer. It is shown that obtained p(HEMA-MAAL) nanopolymer was a reuseable product which protected its adsorption capacity of 98.9% after 5th adsorption-desorption cycle. In conclusion, we suggest a method to develop a nanostructure, selective, low-cost molecularly imprinted polymeric systems with using penicillin G as a template molecule for removal of the antibiotic residues.
Subject(s)
Environmental Monitoring , Models, Chemical , Molecular Imprinting , Nanostructures , Penicillin G/chemistry , Adsorption , PolymersABSTRACT
Two quantum mechanical (QM)-cluster models are built for studying the acylation and deacylation mechanism and kinetics of Streptomyces R61 DD-peptidase with the penicillin G at atomic level detail. DD-peptidases are bacterial enzymes involved in the cross-linking of peptidoglycan to form the cell wall, necessary for bacterial survival. The cross-linking can be inhibited by antibiotic beta-lactam derivatives through acylation, preventing the acyl-enzyme complex from undergoing further deacylation. The deacylation step was predicted to be rate-limiting. Transition state and intermediate structures are found using density functional theory in this study, and thermodynamic and kinetic properties of the proposed mechanism are evaluated. The acyl-enzyme complex is found lying in a deep thermodynamic sink, and deacylation is indeed the severely rate-limiting step, leading to suicide inhibition of the peptidoglycan cross-linking. The usage of QM-cluster models is a promising technique to understand, improve, and design antibiotics to disrupt function of the Streptomyces R61 DD-peptidase.
Subject(s)
Anti-Bacterial Agents/chemistry , Enzyme Inhibitors/chemistry , Penicillin G/chemistry , Serine-Type D-Ala-D-Ala Carboxypeptidase/chemistry , Streptomyces/enzymology , Acylation , Anti-Bacterial Agents/pharmacology , Density Functional Theory , Enzyme Inhibitors/pharmacology , Kinetics , Microbial Sensitivity Tests , Molecular Dynamics Simulation , Molecular Structure , Penicillin G/pharmacology , Serine-Type D-Ala-D-Ala Carboxypeptidase/antagonists & inhibitors , Streptomyces/drug effectsABSTRACT
A biophysical understanding of the mechanistic, chemical, and physical origins underlying antibiotic action and resistance is vital to the discovery of novel therapeutics and the development of strategies to combat the growing emergence of antibiotic resistance. The site-specific introduction of stable-isotope labels into chemically complex natural products is particularly important for techniques such as NMR, IR, mass spectrometry, imaging, and kinetic isotope effects. Toward this goal, we developed a biosynthetic strategy for the site-specific incorporation of 13C labels into the canonical ß-lactam carbonyl of penicillin G and cefotaxime, the latter via cephalosporin C. This was achieved through sulfur-replacement with 1-13C-l-cysteine, resulting in high isotope incorporations and milligram-scale yields. Using 13C NMR and isotope-edited IR difference spectroscopy, we illustrate how these molecules can be used to interrogate interactions with their protein targets, e.g., TEM-1 ß-lactamase. This method provides a feasible route to isotopically labeled penicillin and cephalosporin precursors for future biophysical studies.
Subject(s)
Anti-Bacterial Agents/metabolism , Carbon Isotopes/chemistry , beta-Lactams/metabolism , Anti-Bacterial Agents/chemistry , Binding Sites , Cefotaxime/chemistry , Cefotaxime/metabolism , Cephalosporins/metabolism , Drug Discovery , Drug Resistance, Microbial , Penicillin G/chemistry , Penicillin G/metabolism , Penicillium/metabolism , Protein Conformation , beta-Lactamases/metabolism , beta-Lactams/chemistryABSTRACT
Determining the requirements for efficient oxygen (O2) activation is key to understanding how enzymes maintain efficacy and mitigate unproductive, often detrimental reactivity. For the α-ketoglutarate (αKG)-dependent nonheme iron enzymes, both a concerted mechanism (both cofactor and substrate binding prior to reaction with O2) and a sequential mechanism (cofactor binding and reaction with O2 precede substrate binding) have been proposed. Deacetoxycephalosporin C synthase (DAOCS) is an αKG-dependent nonheme iron enzyme for which both of these mechanisms have been invoked to generate an intermediate that catalyzes oxidative ring expansion of penicillin substrates in cephalosporin biosynthesis. Spectroscopy shows that, in contrast to other αKG-dependent enzymes (which are six coordinate when only αKG is bound to the FeII), αKG binding to FeII-DAOCS results in â¼45% five-coordinate sites that selectively react with O2 relative to the remaining six-coordinate sites. However, this reaction produces an FeIII species that does not catalyze productive ring expansion. Alternatively, simultaneous αKG and substrate binding to FeII-DAOCS produces five-coordinate sites that rapidly react with O2 to form an FeIV=O intermediate that then reacts with substrate to produce cephalosporin product. These results demonstrate that the concerted mechanism is operative in DAOCS and by extension, other nonheme iron enzymes.
Subject(s)
Intramolecular Transferases/chemistry , Iron/chemistry , Ketoglutaric Acids/chemistry , Nonheme Iron Proteins/chemistry , Penicillin-Binding Proteins/chemistry , Reactive Oxygen Species/chemistry , Enzyme Activation , Oxidation-Reduction , Penicillin G/chemistry , Substrate SpecificityABSTRACT
The authors describe an impedimetric aptasensor for Penicillin G (PEN) which is an important antibiotic. The method is based on the use of a pencil graphite electrode (PGE) modified with reduced graphene oxide (RGO) and gold nanoparticles (GNPs) for ultrasensitive detection of PEN. The morphology of a bare PGE, RGO/PGE, and GNP/RGO/PGE, and the functional groups on graphene oxide (GO) and RGO were studied using scanning electron microscopy and Fourier transform infrared spectroscopy. Electrochemical impedance spectroscopy was used for detection of PEN by measuring the charge transfer resistance (Rct). Also, cyclic voltammetry was recorded at potential range of 0.30 to +0.70 V for PGE treatment. This aptamer-based assay has a wide linear range that extends from 1.0 fM to 10 µM, and a limit of detection as low as 0.8 fM. The method was applied to the determination of PEN in spiked milk from cow, sheep, goat and water buffalo. Recoveries ranged from 92% to 104%. The assay is fast, ultrasensitive, high reproducible, and selective over antibiotics such as streptomycin, tetracycline, and sulfadiazine. Graphical abstract Schematic presentation of an impedimetric aptasensor for Penicillin G antibiotic using a pencil graphite electrode (PGE) modified with reduced graphene oxide (RGO) and gold nanoparticles (GNPs). This aptamer based assay has limit of detection as low as 0.8 fM.
Subject(s)
Aptamers, Nucleotide/chemistry , Biosensing Techniques/methods , Food Contamination/analysis , Graphite/chemistry , Metal Nanoparticles/chemistry , Penicillin G/analysis , Animals , Buffaloes , Cattle , DNA/chemistry , Electrochemical Techniques/instrumentation , Electrochemical Techniques/methods , Electrodes , Goats , Gold/chemistry , Limit of Detection , Milk/chemistry , Penicillin G/chemistry , Reproducibility of Results , SheepABSTRACT
Antimicrobial resistance poses a global threat to patient health. Improving the use and effectiveness of antimicrobials is critical in addressing this issue. This includes optimizing the dose of antibiotic delivered to each individual. New sensing approaches that track antimicrobial concentration for each patient in real time could allow individualized drug dosing. This work presents a potentiometric microneedle-based biosensor to detect levels of ß-lactam antibiotics in vivo in a healthy human volunteer. The biosensor is coated with a pH-sensitive iridium oxide layer, which detects changes in local pH as a result of ß-lactam hydrolysis by ß-lactamase immobilized on the electrode surface. Development and optimization of the biosensor coatings are presented, giving a limit of detection of 6.8 µM in 10 mM PBS solution. Biosensors were found to be stable for up to 2 weeks at -20 °C and to withstand sterilization. Sensitivity was retained after application for 6 h in vivo. Proof-of-concept results are presented showing that penicillin concentrations measured using the microneedle-based biosensor track those measured using both discrete blood and microdialysis sampling in vivo. These preliminary results show the potential of this microneedle-based biosensor to provide a minimally invasive means to measure real-time ß-lactam concentrations in vivo, representing an important first step toward a closed-loop therapeutic drug monitoring system.
Subject(s)
Anti-Bacterial Agents/analysis , Biosensing Techniques/methods , Drug Monitoring/methods , Needles , Penicillin G/analysis , Penicillin V/analysis , Anti-Bacterial Agents/chemistry , Biosensing Techniques/instrumentation , Drug Monitoring/instrumentation , Electrochemical Techniques/instrumentation , Electrochemical Techniques/methods , Electrodes , Humans , Hydrolysis , Iridium/chemistry , Limit of Detection , Penicillin G/chemistry , Penicillin V/chemistry , Proof of Concept Study , beta-Lactamases/chemistryABSTRACT
Antibiotic-resistant bacterial infections are a global health problem. A commonly-used antibiotic Penicillin G was incorporated into ZnAl-layered double hydroxides (PNG/LDH) with a varied amount of PNG. PNG/LDH nanocomposites were well characterized in structure and composition using elemental analysis, X-ray diffraction pattern, Fourier transform infrared spectroscopy and TEM images, revealing that PNG were mostly adsorbed on the LDH surfaces at a lower PNG loading but some were intercalated into LDH interlayers at a higher PNG loading. The typical release profile of PNG and Zn2+ from PNG/LDH was a quick release, followed by a sustainable slow release. The antibacterial tests against Escherichia coli demonstrated that PNG/LDH with a suitable composition synergistically improved bacterial inhibition compared with free PNG and pristine LDHs. In specific, PNG/LDH with much higher cost-effectiveness showed a potent antimicrobial activity and maintained the activity for up to 10 days, significantly elongating the antibacterial effect compared with just 1 day for free PNG in the same conditions. Our results suggest suitable composition of nanoparticle carriers and antibiotics could significantly enhance antibacterial activity of antibiotics for a long period via the synergistic effect between carrier and antibiotics, a potential approach to overcome the bacterial resistance to antibiotics.
Subject(s)
Aluminum/chemistry , Anti-Bacterial Agents/pharmacology , Drug Carriers/chemistry , Escherichia coli/drug effects , Hydroxides/chemistry , Penicillin G/pharmacology , Zinc/chemistry , Anti-Bacterial Agents/chemistry , Nanocomposites/administration & dosage , Nanocomposites/chemistry , Penicillin G/chemistryABSTRACT
The determination of antibiotic potency against bacterial strains by assessment of their minimum inhibitory concentration normally uses a standardized broth microdilution assay procedure developed more than 50 years ago. However, certain antibiotics require modified assay conditions in order to observe optimal activity. For example, daptomycin requires medium supplemented with Ca2+, and the lipoglycopeptides dalbavancin and oritavancin require Tween 80 to be added to the growth medium to prevent the depletion of free drug via adsorption to the plastic microplate. In this report, we examine systematically the effects of several different plate types on microdilution broth MIC values for a set of antibiotics against Gram-positive and Gram-negative bacteria, both in medium alone and in medium supplemented with the commonly used additives Tween 80, lysed horse blood, and 50% human serum. We observed very significant differences in measured MICs (up to 100-fold) for some lipophilic antibiotics, such as the Gram-positive lipoglycopeptide dalbavancin and the Gram-negative lipopeptide polymyxins, and found that nonspecific binding plates can replace the need for surfactant additives. Microtiter plate types and any additives should be specified when reporting broth dilution MIC values, as results can vary dramatically for some classes of antibiotics.
Subject(s)
Culture Media/chemistry , Escherichia coli/drug effects , Methicillin-Resistant Staphylococcus aureus/drug effects , Microbial Sensitivity Tests/instrumentation , Aminoglycosides/chemistry , Aminoglycosides/pharmacology , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Calcium/pharmacology , Ciprofloxacin/chemistry , Ciprofloxacin/pharmacology , Colistin/chemistry , Colistin/pharmacology , Culture Media/pharmacology , Depsipeptides/chemistry , Depsipeptides/pharmacology , Escherichia coli/growth & development , Escherichia coli/metabolism , Factor Analysis, Statistical , Lipoglycopeptides/chemistry , Lipoglycopeptides/pharmacology , Methicillin-Resistant Staphylococcus aureus/growth & development , Methicillin-Resistant Staphylococcus aureus/metabolism , Oxacillin/chemistry , Oxacillin/pharmacology , Penicillin G/chemistry , Penicillin G/pharmacology , Plastics/chemistry , Polymyxin B/chemistry , Polymyxin B/pharmacology , Polysorbates/pharmacology , Rifampin/chemistry , Rifampin/pharmacology , Teicoplanin/analogs & derivatives , Teicoplanin/chemistry , Teicoplanin/pharmacology , Trimethoprim/chemistry , Trimethoprim/pharmacology , Vancomycin/chemistry , Vancomycin/pharmacologyABSTRACT
In the present study, efficiency of a new magnetic nanocomposite (CoFe2O4@CuS) for photocatalytic degradation of PG in aqueous solutions was investigated. Structural characteristics of synthesized magnetic nanoparticles were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating-sample magnetometer (VSM), Thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), Energy-dispersive X-ray spectroscopy (EDX) and Raman spectroscopy. Also, the effect of important parameters such as pH (3-11), nanoparticle dosage (0.1-0.8 g/L), PG concentration (10-100 mg/L) and contact time (10-120 min) were investigated. Results of FT-IR, XRD, EDX and Raman analyses showed successful synthesis of CoFe2O4@CuS magnetic nanocomposite. SEM and TEM images showed that the size of CoFe2O4@CuS magnetic nanocomposite was below 100 nm. Also, results of VSM analyses showed that CoFe2O4@CuS magnetic nanocomposite still has magnetic properties (Ms = 7.76 emu/g). According to the results of study, in photocatalytic degradation process of PG by CoFe2O4@CuS magnetic nanocomposite by UV light and in optimum condition (pH = 5, nanocomposite dose: 0.2 g/L, PG concentration: 10 mg/L and contact time: 120 min), maximum degradation of PG was 70.7%. Also the photocatalytic reaction almost followed the pseudo-first order kinetics. In addition, after five consecutive runs, the catalyst efficiency wasn't reduced significantly.
Subject(s)
Cobalt/chemistry , Copper/chemistry , Ferrosoferric Oxide/chemistry , Metal Nanoparticles/chemistry , Penicillin G/chemistry , Wastewater/chemistry , Water Pollutants, Chemical/chemistry , Biodegradation, EnvironmentalABSTRACT
Immobilization of enzyme on the surface of graphene-based composite cellular foams (GCCFs) is commonly prone to acquire stable and ultrahigh loading of enzymes and fast transport of substrates during the catalytic process. In this chapter, we reported a method of preparing GCCFs through combination of redox assembly and biomimetic mineralization with in situ enzyme immobilization. Briefly, GCCFs were first prepared through redox assembly of graphene oxide (GO) nanosheets enabled by polyethyleneimine (PEI). The cationic PEI in the resultant reduced GO/PEI (rGO/PEI) cellular foams acted as the mineralization-inducing agent could catalyze the condensation of silicate to form silica (biomimetic silicification) on the reduced graphene oxide (rGO) surface, where enzyme (with penicillin G acylase as model enzyme) is in situ entrapped and shielded within the silica network. Enzymes could be stably resided on the surface of GCCFs without any leaching against a broad range of pH values (3.5-10.0). GCCFs show a three-dimensional (3D) porous structure, which facilitates the fast transfer of substrate and, thereby, leads to desirable catalytic activity. Combined with the monolithic feature, GCCFs exhibit ease of recyclability and superior thermal/recycling stabilities during the catalytic synthesis of 6-aminopenicillanic acid (6-APA, an important pharmaceutical intermediate) compared to free enzyme and enzyme adsorbed on rGO/PEI cellular foams.
Subject(s)
Enzymes, Immobilized/chemistry , Graphite/chemistry , Nanocomposites/chemistry , Polyethyleneimine/chemistry , Adsorption/drug effects , Oxidation-Reduction , Penicillanic Acid/analogs & derivatives , Penicillanic Acid/chemistry , Penicillin G/chemistry , Porosity/drug effects , Silicon Dioxide/chemistry , Surface PropertiesABSTRACT
An increase in the copper pool in body fluids has been related to a number of pathological conditions, including infections. Copper ions may affect antibiotics via the formation of coordination bonds and/or redox reactions. Herein, we analyzed the interactions of Cu2+ with eight ß-lactam antibiotics using UV-Vis spectrophotometry, EPR spectroscopy, and electrochemical methods. Penicillin G did not show any detectable interactions with Cu2+. Ampicillin, amoxicillin and cephalexin formed stable colored complexes with octahedral coordination environment of Cu2+ with tetragonal distortion, and primary amine group as the site of coordinate bond formation. These ß-lactams increased the solubility of Cu2+ in the phosphate buffer. Ceftazidime and Cu2+ formed a complex with a similar geometry and gave rise to an organic radical. Ceftriaxone-Cu2+ complex appears to exhibit different geometry. All complexes showed 1:1 stoichiometry. Cefaclor reduced Cu2+ to Cu1+ that further reacted with molecular oxygen to produce hydrogen peroxide. Finally, meropenem underwent degradation in the presence of copper. The analysis of activity against Escherichia coli and Staphylococcus aureus showed that the effects of meropenem, amoxicillin, ampicillin, and ceftriaxone were significantly hindered in the presence of copper ions. The interactions with copper ions should be taken into account regarding the problem of antibiotic resistance and in the selection of the most efficient antimicrobial therapy for patients with altered copper homeostasis.