Antibiotics Removal by Continuous Venovenous Hemofiltration with a Novel Asymmetric Triacetate Membrane Hemofilter: An in vitro Study.

INTRODUCTION: Continuous renal replacement therapies (CRRTs) are essential in the treatment of critically ill patients with acute kidney injury and are also discussed as a supporting sepsis therapy. CRRT can affect antibiotics plasma concentrations. OBJECTIVE: The effect of continuous venovenous hemofiltration (CVVH) with an asymmetric triacetate (ATA) membrane hemofilter on concentrations of antibiotics with low (meropenem), medium (vancomycin), and high (daptomycin) protein binding (PB) was investigated. METHODS: 1 L human whole blood supplemented with antibiotics was recirculated and filtrated for 6 h in vitro. Clearances and sieving coefficients (SC) were determined from antibiotics concentrations measured at filter inlet, outlet, and filtrate side. Reservoir concentration data were fitted using a first-order kinetic model. RESULTS: Meropenem and vancomycin concentrations decreased to 5-10% of the initial plasma level, while only 50% of daptomycin were removed. Clearances and SCs were (10.8 [10.8-17.4] mL/min, SC = 0.72 [0.72-1.16]) for meropenem, (13.4 [12.3-13.7] mL/min, 0.89 [0.82-0.92]) for vancomycin, and (2.1 [1.8-2.1] mL/min, 0.14 [0.12-0.14]) for daptomycin. Removal by adsorption was negligible. CONCLUSIONS: The clearances and SCs presented are comparable with findings of other authors. Meropenem and vancomycin, which exhibit low and medium PB, respectively, were strongly removed, while considerably less daptomycin was removed because of its high PB. Our results suggest that in clinical use of the tested antibiotics during CRRT with the ATA hemofilter, the same factors have to be considered for determining the dosing strategy as with filters with other commonly applied membrane materials.

The Seraph®-100 Microbind Affinity Blood Filter Does Not Affect Vancomycin, Tacrolimus, and Mycophenolic Acid Plasma Concentrations.

Extracorporeal blood purification is considered an adjunct therapy in critically ill patients with life-threatening conditions such as sepsis and septic shock. It consists of cytokine removal, removal of endotoxins, a combination of both, or the removal of pathogens themselves. The latter technique was introduced for clinical application very recently. This case study describes a case of a 69-year-old female lung transplant recipient patient with a persistent VV-ECMO-related septic deep vein thrombosis with continuous renal replacement therapy-dependent acute kidney injury initiated on the Seraph®-100 Microbind Affinity Filter in order to control the persistent bacteraemia with coagulase-negative staphylococci. Drug plasma concentrations (vancomycin, tacrolimus, and mycophenolic acid) were measured before and after the device to calculate absorber-related drug clearance.

Simultaneous separation and determination of vancomycin and its crystalline degradation products in human serum by ultra high performance liquid chromatography tandem mass spectrometry method and its application in therapeutic drug monitoring.

A rapid and simple ultra high performance liquid chromatography with tandem mass spectrometry method was developed and validated for the simultaneous separation and determination of vancomycin and its crystalline degradation products in human serum. Vancomycin and two isomers of the degradants were extracted from human serum with a protein precipitation method. The compounds were separated on an Acquity BEH C18 column (2.1 × 50 mm, 1.7 µm) eluted with a gradient mixture of acetonitrile and 0.1% formic acid as the mobile phase. Norvancomycin was used as the internal standard. The linear ranges of vancomycin and two degradant isomers were 1.057-105.7, 0.1437-14.37, and 0.2540-25.40 µg/mL, respectively. The established methods were validated and successfully applied to a therapeutic drug monitoring study of vancomycin in patients with renal insufficiency.

Enantioseparation of chiral pharmaceuticals by vancomycin-bonded stationary phase and analysis of chiral recognition mechanism.

The drug chirality is attracting increasing attention because of different biological activities, metabolic pathways, and toxicities of chiral enantiomers. The chiral separation has been a great challenge. Optimized high-performance liquid chromatography (HPLC) methods based on vancomycin chiral stationary phase (CSP) were developed for the enantioseparation of propranolol, atenolol, metoprolol, venlafaxine, fluoxetine, and amlodipine. The retention and enantioseparation properties of these analytes were investigated in the variety of mobile phase additives, flow rate, and column temperature. As a result, the optimal chromatographic condition was achieved using methanol as a main mobile phase with triethylamine (TEA) and glacial acetic acid (HOAc) added as modifiers in a volume ratio of 0.01% at a flow rate of 0.3 mL/minute and at a column temperature of 5°C. The thermodynamic parameters (eg, ΔH, ΔΔH, and ΔΔS) from linear van 't Hoff plots revealed that the retention of investigated pharmaceuticals on vancomycin CSP was an exothermic process. The nonlinear behavior of lnk' against 1/T for propranolol, atenolol, and metoprolol suggested the presence of multiple binding mechanisms for these analytes on CSP with variation of temperature. The simulated interaction processes between vancomycin and pharmaceutical enantiomers using molecular docking technique and binding energy calculations indicated that the calculated magnitudes of steady combination energy (ΔG) coincided with experimental elution order for most of these enantiomers.

QuEChERS and 96-well plate solid phase extraction for determination of vancomycin and norvancomycin in fish meat by UPLC-MS/MS.

Vancomycin and norvancomycin are glycopeptide antibiotics for gram-positive bacteria infection, but indiscriminately used in aquaculture. In this study, a QuEChERS (quick, easy, cheap, effective, rugged, and safe)/96-well solid-phase extraction (SPE) plate method was used to extract vancomycin and norvancomycin in fish meat samples, and the drugs were further analyzed by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The parameters, such as the sorbent of cation exchange resin, the proportion of acetonitrile (15%) in extractant, the mobile phase of water (0.1% formic acid)/acetonitrile, were optimized. The method was validated in terms of linearity (0.9990-0.9994), LOD (0.51 µg·kg-1), LOQ (1.73 µg·kg-1), intra-dayprecision (<5.19%), inter-day precision (<6.30%), and recovery (86.7-98.6%). Finally, the method was successfully applied to contaminated and randomly collected samples. The results indicated that the proposed method meet the daily monitoring requirements for vancomycin and norvancomycin.

Microcolumn LC enantioseparation of chiral compounds using diol silica gel functionalized with vancomycin crystalline degradation products.

Vancomycin crystalline degradation products (CDPs) have been introduced as one of the newest and most interesting derivatives of vancomycin for enantiomer separation of a wide variety of chiral compounds. In this attempt, a chiral stationary phase (CSP) has been prepared using diol silica gel based on vancomycin CDPs which led to a new chiral selector with new functionality of functional groups on a microcolumn LC. Different kinds of mobile phases were examined to realize the behavior of the chiral selector in separation of atropine, fluoxetine, amlodipine, mandelic acid, alanine, and phenylalanine which were separated successfully on this column. Good results were obtained by using a polar mobile phase containing water, methanol, and acid additives for separation of chiral acidic compounds and amino acid samples. Considerable results were obtained for analysis of basic compounds by using polar organic mobile phase (POP) containing methanol, acid and base additives. These results can be associated with the presence of the carboxylic acid groups present in new CSP by using a diol silica gel.

Surface Design of Enantiomeric HPLC Separation on Vancomycin and Teicoplanin-Based Stationary Phases, a Tool for Chiral Recognition of Model ß-Blockers.

A quality-by-design approach was adopted for enantioseparation of atenolol on Vancomycin and Teicoplanin-based chiral stationary phases using reversed phase (RP) mode and polar ionic mode (PIM), respectively to account for major forces involved in enantiorecognition of ß-blockers on macrocyclics. A fractional factorial screening design for the two modes; followed by a central composite optimization design and regression analysis were able to point out critical factors and chromatographic responses and robust surface of the design. Within the studied range of flow the optimal was 0.3 mL/min for Chirobiotic T and 1 mL/min for Chirobiotic V. In PIM, a composition of 100% methanol was mandatory to compromise between best separation and least retention with equal amounts of the acid and base modifiers for enantiomers of atenolol, as model drug in addition to metoprolol and pindolol as structurally related compounds for possible extrapolation of results on members of the same class. However, in RP mode, only triethylamine acetate was needed as buffer for atenolol enantiomers. Chiral recognition of atenolol in both elution modes, further confirmed via extrapolation of the models on the two other ß-blockers showed that ionic interactions rather than any other forces governed chiral recognition on the two macrocyclic stationary phases in both modes.

Light-assisted preparation of vancomycin chiral stationary phase based on diazotized silica and its enantioseparation evaluation by high-performance liquid chromatography.

Owing to enantiomers' identical physical and chemical properties, separation work in the chiral environments is still a great challenge.and chemical properties. Chromatographic techniques employing chiral stationary phases (CSPs) have been developed as powerful tools for the chiral analysis and preparation of pure enantiomers. Here we report a facile synthesis of vancomycin stationary phase based on diazotized silica. Monodisperse silica particles were synthesized by a modified Stöber method. The obtained silica particles were modified by self-assembly photosensitive diazoresin (DR) and vancomycin on the surface. After treatment with UV light, the ionic bonding was converted into covalent bonding through a unique photochemistry reaction of DR. Baseline separation of chiral drugs was achieved by using the vancomycin@SiO2 particles as packing materials in high performance liquid chromatography (HPLC). The effects of separation parameters including elution mode, flow rate and analyte mass on the enantioselectivity of the CSP were investigated in detail. Due to the replacement of highly toxic and moisture sensitive silane agent by water soluble non-toxic DR in the modification of silica microspheres, this method provides a green and easy way to manufacture packing materials for chromatography applications.

Residual antibiotics in allograft heart valve tissue samples following antibiotic disinfection.

Antibiotics are routinely used for the decontamination of allograft heart valves. To monitor the efficacy of this process, samples of tissue are sent for microbiological analysis. This investigation was undertaken to determine residual antibiotic concentrations in decontaminated tissue and to assess the likely inhibitory effect on microbiological cultures. After a typical decontamination protocol, both gentamicin and vancomycin were present in all tissue samples and the majority of enrichment broths at concentrations sufficient to inhibit most bacteria. The data presented indicate that protocols used by heart valve banks and associated microbiology laboratories should be reviewed, and support the use of predecontamination cultures to identify particularly virulent micro-organisms.

Chromatographically purified vancomycin: therapy of serious infections caused by Staphylococcus aureus and other gram-positive bacteria.

Fourteen patients with serious infections caused by Staphylococcus aureus and other gram-positive bacteria were prospectively treated with chromatographically purified vancomycin in an open-label, nonrandomized study, between December 1986 and June 1987. Five patients were excluded from the evaluation of efficacy. Among the nine evaluable patients, cure was achieved in six patients--a success rate of 67%. One patient had a relapse of osteomyelitis, and cultures of draining pus were positive for oxacillin-resistant S aureus within three weeks after the discontinuation of vancomycin therapy. One patient failed to respond to vancomycin therapy for S aureus-induced endocarditis, meningitis, and osteomyelitis; in another patient, the treatment failed to reverse the course of S aureus septicemia. No serious drug toxicity, for example, nephrotoxicity, was encountered in any patient. One patient (7%) experienced mild ototoxicity. Four patients (29%) had mild phlebitis, two patients (14%) had a transiently positive Coombs' test, and one patient (7%) had a "red neck syndrome" and "pain and spasm syndrome." Chromatographically purified vancomycin is an effective antibiotic in the treatment of serious infections caused by susceptible gram-positive bacteria. Some minor side effects of vancomycin may not be due to impurities in the preparation but rather to the vancomycin itself.

Development and validation of an improved method for the analysis of vancomycin by liquid chromatography selectivity of reversed-phase columns towards vancomycin components.

The current method prescribed in official monographs for the purity control of vancomycin is inappropriate in that several components are not separated from each other and other components are coeluted with the main component vancomycin B. The method uses an ODS column at pH 3.2. In this study, several changes were introduced in order to improve the separation. The optimization of the separation method at low pH indicated that pH 1.7 was optimum and that the use of dioxane as organic modifier drastically improved the separation. These conditions were used to test a set of more than 40 reversed-phase columns for their selectivity towards vancomycin components. The selection of the most suitable columns was performed by means of principal component analysis. Most of these columns did not allow the separation of didechlorovancomycin from monodechlorovancomycin 1. It was found that neutral to slightly alkaline mobile phases allowed better separation. Further optimization of the separation method and a robustness study were performed by means of experimental design. This optimization indicated that pH 7.7 was optimum and gradient elution was also used to effect complete analysis. The final method uses a Kromasil column and the mobile phase comprises dioxane, water and ammonium formate solution pH 7.7. The separation of monodechlorovancomycin 2 and of some unknown impurities from the main component vancomycin B is described for the first time. The method shows good repeatability, linearity and sensitivity.

Partitioning of vancomycin using poly(ethylene glycol)-coupled ligands in aqueous two-phase systems.

Affinity partitioning describes a process in which a biospecific ligand is used to manipulate the partitioning behavior of a biomolecule by coupling a ligand to one of the phase-forming polymers. It combines the high selectivity of affinity chromatography with the scalability of aqueous two-phase extractions. Fundamental studies have been made on the factors affecting affinity partitioning of the antibiotic vancomycin using a series of polymer-ligands composed of the D-Ala-D-Ala peptide coupled to poly(ethylene glycol) in methoxypoly(ethylene glycol)/dextran aqueous two-phase systems. The effects of varying the ligand molecular weight, the ligand binding interaction, the number of binding sites, the tie-line length, and the aggregation of vancomycin have been measured. A modification of the Flanagan and Barondes model for affinity partitioning has been suggested to explain the results. The modified model accounts for the changes in the surface properties of the biomaterial on complex formation.

High performance liquid chromatography (HPLC) of antibiotics of vancomycin type. Comparative studies.

Comparative HPLC examination of seven antibiotics of vancomycin type has been undertaken. Investigation has shown that on column I in eluent system B, ristomycin A (ristocetin A) can be not only separated from vancomycin, but both antibiotics can be quantitatively determined. Under these conditions the lowest detectable quantities of the individual antibiotics have been also stated. By the application of this column and eluent system A, ristomycin A (ristocetin A) and the major component of the A-35512 B antibiotic complex can be readily separated from one-another and from avoparcin alpha and beta.

Actinoidin A2, a novel glycopeptide: production, preparative HPLC separation and characterization.

An unidentified Nocardia sp. (SK&F-AAJ-193) was isolated and found to produce actinoidin A and a novel analog which we have named actinoidin A2. This new glycopeptide antibiotic differs from actinoidin A by the presence of rhamnose instead of acosamine. This analog was isolated using Dianion HP-20 resin followed by a specific glycopeptide affinity column (Affigel-10-D-Ala-D-Ala). The purification was accomplished using preparative ion-pairing chromatography. Actinoidin A2 is active against Staphylococcus aureus and coagulase-negative Staphylococci although it is less potent than actinoidin A.

Balhimycin, a new glycopeptide antibiotic produced by Amycolatopsis sp. Y-86,21022. Taxonomy, production, isolation and biological activity.

A new glycopeptide antibiotic, balhimycin, has been isolated from the fermentation broth of a Amycolatopsis sp. Y-86,21022. Balhimycin belongs to the vancomycin class of glycopeptides and contains a dehydrovancosamine sugar. The biological activity of balhimycin has been compared extensively with that of vancomycin against methicillin resistant staphylococci and also against anaerobes. Balhimycin is marginally superior to vancomycin in its in vitro activity against anaerobes and in its bactericidal properties.

Activity of linezolid and daptomycin against methicillin-resistant coagulase-negative staphylococci with increased MIC for vancomycin isolated from blood cultures in pediatric patients.

We evaluated minimal inhibitory concentration (MIC) for vancomycin, daptomycin, and linezolid in methicillin-resistant coagulase-negative staphylococci (MR-CoNS). Minimal inhibitory concentration of 2-4 mg/l for vancomycin was observed in 16% of strains, and among them 19% had MIC at breakpoint for daptomycin or linezolid. Among strains completely susceptible to vancomycin, 16% had MIC at breakpoint for daptomycin and 11% had for linezolid. This large proportion of pathogens with MIC around the breakpoint suggests a possible risk of treatment failure with these drugs. This phenomenon is worth further and constant monitoring.

Identifying producers of antibacterial compounds by screening for antibiotic resistance.

Microbially derived natural products are major sources of antibiotics and other medicines, but discovering new antibiotic scaffolds and increasing the chemical diversity of existing ones are formidable challenges. We have designed a screen to exploit the self-protection mechanism of antibiotic producers to enrich microbial libraries for producers of selected antibiotic scaffolds. Using resistance as a discriminating criterion we increased the discovery rate of producers of both glycopeptide and ansamycin antibacterial compounds by several orders of magnitude in comparison with historical hit rates. Applying a phylogeny-based screening filter for biosynthetic genes enabled the binning of producers of distinct scaffolds and resulted in the discovery of a glycopeptide antibacterial compound, pekiskomycin, with an unusual peptide scaffold. This strategy provides a means to readily sample the chemical diversity available in microbes and offers an efficient strategy for rapid discovery of microbial natural products and their associated biosynthetic enzymes.

Elimination of teicoplanin by adsorption to the filter membrane during haemodiafiltration: screening experiments for linezolid, teicoplanin and vancomycin followed by in vitro haemodiafiltration models for teicoplanin.

Pharmaceutical agents directed against methicillin-resistant Staphylococcus aureus can be eliminated during haemodiafiltration, not only by diffusion and ultrafiltration, but also by adsorption onto haemofilters. The latter may be affected by the binding of agents to serum albumin. The present study therefore investigated the affinity of anti-methicillin-resistant Staphylococcus aureus agents (teicoplanin, linezolid, vancomycin) for haemofilters and the pharmacokinetic properties of teicoplanin during haemodiafiltration. Linezolid, teicoplanin and vancomycin were first screened for their in vitro affinity for three different kinds of filter membranes: polysulfone, polyacrylonitrile and polymethylmethacrylate. Only teicoplanin showed significant filter-binding activity. An in vitro haemodiafiltration circulation model was then developed that incorporated a one-litre beaker containing Krebs-Ringer's bicarbonate solution with/without human albumin (0 or 3 g/dl) as an artificial plasma. Teicoplanin (initial concentration 50 µg/ml, representing the maximum plasma concentration (Cmax) resulting from a typical clinical dosage) was circulated throughout the beaker. Teicoplanin concentrations in the 'plasma' and ultrafiltrate were determined by high performance liquid chromatography. In the screening experiment, teicoplanin was predominantly adsorbed onto polysulfone and polymethylmethacrylate membranes. Furthermore, teicoplanin was primarily eliminated by adsorption onto these filters during in vitro haemodiafiltration. Albumin significantly reduced both haemodiafiltration clearance and the adsorption-dependent elimination, although there were complex but significant interactions between albumin and the filter membrane. Elimination of teicoplanin in an in vitro haemodiafiltration model was largely due to adsorption onto polysulfone and polymethylmethacrylate haemofilters. Future clinical studies should likely be designed to evaluate present recommendations of teicoplanin dosages in patients on haemodiafiltration.