Recent Trends in Therapeutic Drug Monitoring of Peptide Antibiotics

Antimicrobial peptides take a specific position in the field of antibiotics (ATBs), however, from a large number of available molecules only a few of them were approved and are used in clinics. These therapeutic modalities play a crucial role in the management of diseases caused by multidrug-resistant bacterial pathogens and represent the last-line therapy for bacterial infections. Therefore, there is a demand for a rationale use of such ATBs based on optimization of the dosing strategy to minimize the risk of resistance and ensure the sustainable efficacy of the drug in real clinical practice. Therapeutic drug monitoring, as a measurement of drug concentration in the body fluids or tissues, results in the optimization of the patient´s medication and therapy outcome. This strategy is beneficial and could result in tailored therapy for different types of infection and the prolongation of the use and efficacy of ATBs in hospitals. This review paper provides an actual overview of approved antimicrobial peptides used in clinical practice and covers current trends in their analysis by convenient and advanced methodologies used for their identification and/or quantitation in biological matrices for therapeutic drug monitoring purposes. Special emphasis is given to the methods with perspective clinical outcomes.

Comparison of vancomycin assays in patients undergoing hemodialysis

Vancomycin is a glycopeptide antibiotic mainly excreted by glomerular filtration. Therefore, patients undergoing hemodialysis tend to accumulate its crystalline degradation product, which has been associated with cross-reaction in commercial immunoassays. The aim of this study was to assess the performance of two commercial immunoassays for measuring vancomycin levels in patients undergoing hemodialysis. This method-comparison study enrolled patients undergoing hemodialysis at two hospitals in Porto Alegre, Brazil. Vancomycin serum concentrations measured by Chemiluminescent Microparticle Assay (CMIA) and measured by Kinetic Interaction of Microparticles in Solution (KIMS) were compared with Liquid Chromatography coupled with Tandem Mass Spectrometry (LC-MS/MS). A total of 64 samples from 42 patients and 54 samples from 23 patients were included in CMIA and KIMS groups. Both measurements were highly correlated with LC-MS/MS, with Spearman rank correlation coefficient r = 0.840 (p < 0.001) and r = 0.926 (p < 0.001), respectively. No deviation of linearity was observed (p = 0.81 and p = 0.49, respectively). The mean difference between CMIA and LC-MS/MS was -1.19 μg/mL and between KIMS and LC-MS/MS was -2.28 μg/mL. LC-MS/MS measured levels were, on average, 2.64 % higher than CMIA and 8.81 % higher than KIMS. CMIA and KIMS revealed accurate commercial methods to measure vancomycin serum concentrations in patients undergoing hemodialysis.

Development and validation of a dried plasma spot LC-MS/MS method for therapeutic monitoring of vancomycin and comparison with enzyme-multiplied immunoassay

Vancomycin is used as an antimicrobial agent for the treatment of severe gram-positive infections. The importance of therapeutic monitoring of antimicrobials has led to the development of more specific sample preparation techniques capable of identifying with accuracy the concentration of this substance in the organism. An aliquot of 10 μl of plasma was transferred to Whatman 903 paper and dried at room temperature. The extraction method was performed by cutting and transferring the paper to a microtube and adding sodium phosphate buffer and internal standard. The mixture was shaken and centrifuged, and a 5-μl aliquot was injected into the analytical system. The optimization of the main parameters that can influence the extraction efficiency was performed using multivariate approaches to obtain the best conditions. The method developed was validated, providing coefficients of determination higher than 0.994 and a lower limit of quantification of 1 mg/L. Within- and between-run precision ranged from 11.4 to 17.30% and from 6.65 to 13.51%, respectively. This method was successfully applied to 75 samples of patients undergoing vancomycin therapy. The method was rapid, simple, and environmentally friendly with satisfactory analytical performance and was advantageous over the laborious and time-consuming methodologies used in therapeutic drug monitoring routine analyses.

Simple and rapid method for analysis of urinary vancomycin using solid phase extraction and fluorescence spectroscopy

Vancomycin (VCM) is an antimicrobial that is recommended for therapeutic drug monitoring (TDM) for maintaining the efficacy and safety of treatment. The trough monitoring has been used to guide VCM dosing regimens. However, newer guidelines recommend the use of area under the curve/minimum inhibitory concentration (AUC/MIC)-guided vancomycin dosing, and there is a need for easier and more frequent measurements of VCM concentrations. Therefore, in this study, we developed a simple and rapid analytical method for measuring urinary VCM by combining solid-phase extraction and fluorescence analysis. Urine samples are easier and less invasive than blood samples. In addition to the therapeutic range of blood VCM, this method was also able to measure 0.01–1 mg/mL, which is the concentration range of urinary VCM. The accuracy of 10, 20, and 30 μg/mL VCM solutions were between 93.18 and 109.76%. The relative standard deviation (RSD) of intra-day and inter-day analysis were less than 6.25% and 6.28%, respectively. Since this method does not use large equipment, it is expected to be better suited for clinical use.

Simultaneous detection of foodborne pathogenic bacteria in milk by fluorescence immunoassay

Rapid, sensitive and simultaneous detection of multiple bacteria in foodborne is still a major challenge in public health field. Here, a fluorescence immunoassay that can achieve high-throughput detection of three Gram-positive foodborne pathogenic bacteria simultaneously was proposed. Vancomycin and bovine serum albumin conjugate (Van-BSA) was immobilized on a polycarbonate chip to capture three Gram-positive foodborne pathogenic bacteria, Staphylococcus aureus (S. aureus), Bacillus cereus (B. cereus) and Listeria monocytogenes (L. monocytogenes). CdSe/ZnS quantum dot modified antibodies (Ab-QD) were prepared by carbodiimide coupling chemistry. Due to the affinity reaction between antibodies and proteins on the bacterial surface, the simultaneous detection of multiple Gram-positive bacteria was achieved by monitoring the fluorescence signal of quantum dot by a portable microfluidic chip analyzer. Under optimal conditions, low detection limits was 18 CFU/well, 3 CFU/well and 36 CFU/well for S. aureus, B. cereus and L. monocytogenes, respectively. With satisfactory accuracy and precision, the proposed fluorescence immunoassay holds good prospects to detect pathogens in real food samples.

Liquid chromatographic methods in the determination of inosine monophosphate dehydrogenase enzyme activity: a review

Inosine monophosphate dehydrogenase (IMPDH) is a crucial enzyme involved in the de novo synthesis of purine nucleotides. IMPDH activity is used to evaluate the pharmacodynamics/pharmacokinetics of immunosuppressant drugs such as mycophenolic acid and thiopurines. These drugs are often used to prevent organ transplant rejection and as steroid-sparing agents in autoinflammatory diseases such as inflammatory bowel disease and rheumatoid arthritis. Numerous analytical techniques have been employed to evaluate IMPDH activity in biological matrices. However, hyphenated LC techniques were most widely used in the literature. This review focuses on hyphenated LC methods used to measure IMPDH activity and provides detailed insight into the sample preparation techniques, chromatographic conditions, enzymatic assay conditions, detectors and normalization factors employed in those methods.

Pharmacokinetic assessment of vancomycin in critically ill patients and nephrotoxicity prediction using individualized pharmacokinetic parameters

Introduction: Therapeutic drug monitoring (TDM) and pharmacokinetic assessments of vancomycin would be essential to avoid vancomycin-associated nephrotoxicity and obtain optimal therapeutic and clinical responses. Different pharmacokinetic parameters, including trough concentration and area under the curve (AUC), have been proposed to assess the safety and efficacy of vancomycin administration. Methods: Critically ill patients receiving vancomycin at Nemazee Hospital were included in this prospective study. Four blood samples at various time intervals were taken from each participated patient. Vancomycin was extracted from plasma samples and analyzed using a validated HPLC method. Results: Fifty-three critically ill patients with a total of 212 blood samples from June 2019 to June 2021 were included in this study. There was a significant correlation between baseline GFR, baseline serum creatinine, trough and peak concentrations, AUCτ, AUC24h, Cl, and Vd values with vancomycin-induced AKI. Based on trough concentration values, 66% of patients were under-dosed (trough concentration <15 μg/ml) and 18.9% were over-dosed (trough concentration ≥20 μg/ml). Also, based on AUC24h values, about 52.2% were under-dosed (AUC24h < 400 μg h/ml), and 21.7% were over-dosed (AUC24h > 600 μg h/ml) that emphasizes on the superiority of AUC-based monitoring approach for TDM purposes to avoid nephrotoxicity occurrence. Conclusion: The AUC-based monitoring approach would be superior in terms of nephrotoxicity prediction. Also, to avoid vancomycin-induced AKI, trough concentration and AUCτ values should be maintained below the cut-off points.

Surface molecularly imprinted solid-phase extraction for the determination of vancomycin in plasma samples using HPLC-MS/MS

Vancomycin is a glycopeptide antibiotic used to treat infections caused by Gram-positive bacteria. Due to the narrow therapeutic index of vancomycin, it is necessary to develop a sensitive and reliable analytical method to monitor the drug concentration in plasma. A novel method based on surface molecularly imprinted solid-phase extraction combined with liquid chromatography-tandem mass spectrometry for the determination of vancomycin in plasma sample was developed. The plasma sample was cleaned up through the solid-phase extraction process before the analysis. The calibration standard of vancomycin in plasma ranged between 1 and 100 ng/mL, and the correlation coefficient (r) was 0.9993. The average recoveries were from 94.3 to 104.0%, and the precision was less than 10.5%. The limit of detection and limit of quantification were 0.5 ng/mL and 1 ng/mL, respectively. The method validated was successfully used for the detection of vancomycin in mice after oral administration.

Determination of Vancomycin and Norvancomycin Residues in Milk by Automated Online Solid-Phase Extraction Combined With Liquid Chromatography-High Resolution Mass Spectrometry

Background

Vancomycin and norvancomycin, as potent antibacterial retention drugs, were used illegally on animals bred for food, which directly affected the quality and safety of animal-derived food, and even harmed human health.

Objective

A fast analysis method, which was adopted to detect residues of vancomycin and norvancomycin in milk, was implemented on a chromatographic system containing online solid-phase extraction (SPE) device that combined with high-resolution mass spectrometer (HRMS).

Method

First, the analytes were added to the blank milk sample were extracted with water [containing 0.1% trifluoroacetic acid (TFA)]–acetonitrile (ACN) (8:2, v/v), and then were purified and enriched on a C18-XL column, whereafter eluted from the purification column onto the analytical column (Shiseido Capcell Pak ADME column) for chromatographic separation prior to hybrid quadrupole–Orbitrap (Q-Orbitrap) detection.

Results

The results showed that the limit of detection (LOD) for each analyte and the limit of quantitation (LOQ) were 0.15  and 0.5 μg/kg, respectively. The correlation coefficient(s) of vancomycin and norvancomycin ranged from 0 to 200 ng/mL were greater than 0.9983.

Conclusions

These validations reflected that it was suitable for the established method to rapidly analyze vancomycin and norvancomycin residues in milk.

Highlights

The method for detecting vancomycin and norvancomycin residues in milk by online SPE combined with LC-HRMS. Online SPE technology realized automation, and the application of HRMS greatly improved the reliability of qualitative and quantitative analyses. The developed method is fast, simple, and reliable; each methodological index can meet requirements of trace analyses of vancomycin and norvancomycin in milk.

A novel sensitive analytical method for the simultaneous analysis of vancomycin and teicoplanin in human urine via single high-performance liquid chromatography coupled with photodiode array and mass spectrometry in series

Analysis of vancomycin and teicoplanin in biological fluids is vital since they are used in the treatment of hospital infections. For the determination of both glycopeptides in urine, a sensitive and accurate analytical method using high‐performance liquid chromatography coupled with photodiode array and mass spectrometry was developed and validated. This research work is the first attempt to develop a chromatographic method for the determination of two glycopeptides with structural similarities. Moreover, the used non‐invasive sampling method is an advantage of this research effort, especially when the blood sampling is difficult. Urine was treated with acetonitrile and 5% trichloroacetic acid, followed by solid‐phase extraction. The chromatographic separation was established at a C18 column (4.6 × 150 mm, 5 μm), using a gradient method and an electrospray ionization source in a positive mode. The linearity of the method was R²≥ 0.9900. The precision was estimated with a maximum coefficient of variation below 15%, while the accuracy ranged from 64 to 121%. The limit of detection and quantification of both glycopeptides ranged from 0.076 up to 0.33 mg/L and 0.33 up to 2.1 mg/L, respectively, showing the same sensitivity as the triple quadrupole mass spectrometry, which is the most frequently used method.

Development of an in-syringe gas-assisted density tunable solidification of floating organic droplet-based dispersive liquid phase microextraction method coupled with HPLC-MS/MS for monitoring amikacin in biological fluids

A new sample preparation method named in-syringe gas-assisted density tunable dispersive liquid phase microextraction based on solidification of floating organic droplet has been introduced. This method was coupled with high-performance liquid chromatography-tandem mass spectrometry and used for the extraction and quantification of amikacin in plasma and exhaled breath condensate (EBC) samples of the patients receiving amikacin. In the proposed approach, an inert gas is bubbled into a syringe barrel containing aqueous solution of the analyte and a mixture of low density extraction solvent and volatile density modifier. Consequently, the density modifier is evaporated and the analyte is migrated into the released extractant droplets. Basic parameters affecting efficiency of the developed method were optimized. Under optimum conditions, the method limits of detection were 0.06 and 0.29 ng/mL in EBC and plasma, respectively. The extraction recoveries were 90% and 87% in EBC and plasma, respectively. Also, the obtained relative standard deviations were below 9.5% and 9.8% for EBC and plasma, respectively. Considering these results, the developed method provides a quick and efficient way to determine amikacin in patients' biological fluids and can be used widely in drug monitoring and clinical studies.

Vancomycin recognition and induced-aggregation of the Au nanoparticles through freeze-thaw for foodborne pathogen Staphylococcus aureus detection

Infectious diseases caused by foodborne pathogens have become a serious public health problem. It is urgent to develop simple, rapid, and visual methods for pathogen detection. Herein, gold nanoparticles (AuNPs), aptamer and vancomycin (Van) based dual-recognition molecules and magnetic enrichment were combined to realize visual detection of Staphylococcus aureus (S. aureus). Initially, S. aureus was bounded to aptamer coupled Fe₃O₄ with high affinity and selectivity, which can achieve the separation and enrichment of S. aureus in complex sample matrix. Subsequently, the second recognition molecule, Van, was conjugated to S. aureus -Apt - Fe₃O₄. Finally, the unbound Van supernatant was dropped in AuNPs solution that induced the aggregation of the AuNPs through freeze-thaw. Firstly, it was found that AuNPs were stable in the presence of Van after a freeze-thaw cycle. A facile visual colorimetric detection of S. aureus was constructed with the linear range from 10¹ to 10⁴ CFU/mL and the limit of detection (LOD) of 0.2 CFU/mL. By altering the aptamer, this method can be extended to the other Gram-positive bacteria. The proposed method has great potential applications in monitoring food contamination and infectious diseases.

Recent advances in the chromatographic determination of the most commonly used anti-hepatitis C drug sofosbuvir and its co-administered drugs in human plasma

Sofosbuvir is a direct-acting antiviral drug that inhibits hepatitis C virus (HCV) NS5B polymerase, which in turn affects the virus replication inside biological systems. The clinical importance of sofosbuvir is based not only on its effect on HCV but also on other lethal viruses such as Zika and severe acute respiratory syndrome coronavirus disease 2019 (SARS-COVID-19). Accordingly, there is a continuous shedding of light on the development and validation of accurate and fast analytical methods for the determination of sofosbuvir in different environments. This work critically reviews the recent advances in chromatographic methods for the analysis of sofosbuvir and/or its metabolites in pure samples, pharmaceutical dosage forms, and in the presence of other co-administered drugs to highlight the current status and future perspectives to enhance its determination in different matrixes.

A new HPLC-MS/MS analytical method for quantification of tazobactam, piperacillin, and meropenem in human plasma

A simple and fast high-performance liquid chromatography with tandem mass spectrometry method for quantification of tazobactam, piperacillin, and meropenem in human plasma has been developed and validated. Simple sample preparation with a volume of 10 μL was done by protein precipitation with a mixture of methanol-acetonitrile-water (6:2:2, v/v/v). Chromatographic separation was achieved on a Luna column with a precolumn security guard by gradient elution using a mobile phase consisting of water with the addition of 0.1% formic acid (component A) and mixture methanol-acetonitrile (8:2, v/v) with the addition of 0.1% formic acid (component B). The run time was 2.7 min. The lower limits of detection and lower limits of quantification were for piperacillin 0.03 and 0.1 mg/L, for meropenem 0.04 and 0.2 mg/L and for tazobactam 0.16 and 0.5 mg/L. The validated method was used for therapeutic monitoring of tazobactam, piperacillin, and meropenem in samples of patients treated in the intensive care unit.

Dual-emission fluorescence biosensing of vancomycin based on AIEgen-peptide conjugates and aptamer-modified Au nanoclusters

Precise doses of antibiotics are necessary to prevent bacterial drug resistance. Although fluorescent sensors are promising for quantitative analyses of antibiotics, improvements in feasibility, selectivity, and sensitivity are needed. In this study, a dual-emission fluorescence biosensor platform was developed for simple, selective, and sensitive determination of vancomycin (Van) based on a peptide conjugated with blue-emitting aggregation-induced emission luminogens (AIEgen) and aptamer-modified red-emitting gold nanoclusters (AuNCs-apt). The peptide and aptamer together recognized Van with high affinity, thus changing the fluorescence intensity at 470 nm and 650 nm, respectively. This platform displayed excellent linear correlation between the fluorescence response and a Van concentration ranging 0.01-100 μg mL^-1, and the limit of detection (LOD) was 2.79 ng mL^-1. In addition to the ability to accurately distinguish Van from glycopeptide antibiotics, the newly developed biosensor allowed for naked-eye detection of 1 μg mL^-1 Van. These results and those of serum samples and microdialysate samples support the application of this newly developed method for Van monitoring and clinical diagnosis.

Toxicity Profile and Pharmacokinetic Study of Antibiotic Mixtures, Gentamicin and Vancomycin, in Rat Plasma by Ecofriendly Liquid Chromatography Coupled Tandem Mass Spectrometry

The global burden of bacterial infection and antimicrobial resistance increases the demand to associate more than one antibiotic to fight life-threatening bacteria. Therefore, there is a great necessity to develop simple and sensitive methods for routine analysis of clinical samples. Therapeutic drug monitoring, bioequivalence, and pharmacokinetic studies are essential to ensure drug efficiency and safety. Herein, therefore, the first ecofriendly liquid chromatography -tandem mass spectrometry (LC-MS/MS) method was developed and fully validated for simultaneous determination of a commonly combined antibiotic for methicillin-resistant Staphylococcus aureus (MRSA), vancomycin (VCM) and gentamicin (GTM), in rat plasma after parenteral administration. VCM and GTM were extracted from plasma sample using acetonitrile (ACN)/0.1% TFA-induced protein precipitation followed by the separation on an Agilent Eclipse Plus ODS (3 mm × 100 mm, 3.5 μm) column using water-enriched mobile phase consisting of water containing 0.1% THF/ACN (85:15, v/v%) at flow rates of 0.30 mL min^-1. The mass spectrometry parameters were optimized, and multiple reaction monitoring (MRM) in positive ion mode of two transitions was utilized for quantification of precursor to product ion at m/z 725.5 → 144 and 100.1 for VCM as [M + 2H]²⁺, 478.3 → 322.2 and 156.9 for GTM, and 586.3 → 162.9 and 425.3 for amikacin (AMK) internal standard, as [M + H]⁺. The current method has been validated as per U.S. FDA bioanalytical guidelines in terms of linearity, accuracy, precision, selectivity, recovery, matrix effects, and stability. The method was linear in the range of 1-2000 ng mL^-1 and 1-1000 ng mL^-1 with detection limits (S/N of 3) of 0.18 and 0.09 ng mL^-1 for VCM and GTM, respectively. The selectivity and high sensitivity allow the current method to succeed in the study of pharmacokinetic parameters and drug-drug interaction between VCM and GTM after single-dose administration. VCM increased plasma clearance and elimination rate constant of GTM when coadministered and GTM also too. The change of serum chemistry analysis and significant elevation of creatinine and BUN indicate an alteration in kidney function in group III in those given the combined antibiotics. Our finding illustrated the nephrotoxicity of the two drugs when associated. The ecofriendly, simplicity, and rapidity of the current study made it a promising method for high-throughput biomonitoring in clinical samples.

Antibiotic and mammal IgG based lateral flow assay for simple and sensitive detection of Staphylococcus aureus

Lateral flow assay (LFA), performed with simple devices and short detection time, is popular in field applications. Herein, a novel sandwich type-based LFA was constructed for high sensitivity and selectivity detection of Staphylococcus aureus (S. aureus). Vancomycin-immobilized gold nanoparticles (VAN-Au NPs) were utilized as the first identifier to capture S. aureus and the specificity was guaranteed by the second recognition agent of pig immunoglobulin G (IgG). In addition, gold growth was adopted for signal amplification to further improve the detection sensitivity. S. aureus could be directly assayed by this LFA within the concentration range of 1.0 × 10³-1.0 × 10⁸ cfu mL^-1 with a detection limit of 1.0 × 10³ cfu mL^-1. Furthermore, the novel sandwich LFA realized S. aureus detection in food samples with admissible recoveries and established a rapid, simple, cost-effective and sensitive platform, could meet the demand for on-site testing of S. aureus.

Nebulization of Vancomycin Provides Higher Lung Tissue Concentrations than Intravenous Administration in Ventilated Female Piglets with Healthy Lungs

BACKGROUND

Intravenous vancomycin is used to treat ventilator-associated pneumonia caused by methicillin-resistant Staphylococcus aureus, but achieves high rates of failure. Vancomycin nebulization may be efficient to provide high vancomycin lung tissue concentrations. The aim of this study was to compare lung tissue and serum concentrations of vancomycin administered intravenously and by aerosol in mechanically ventilated and anesthetized healthy piglets.

METHODS

Twelve female piglets received a single intravenous dose of vancomycin (15 mg/kg) and were killed 1 (n = 6) or 12 h (n = 6) after the end of administration. Twelve piglets received a single nebulized dose of vancomycin (37.5 mg/kg) and were killed 1 (n = 6) or 12 h (n = 6) after the end of the aerosol administration. In each group, vancomycin lung tissue concentrations were assessed on postmortem lung specimens using high-performance liquid chromatography. Blood samples were collected for serum vancomycin concentration measurement 30 min and 1, 2, 4, 6, 8, and 12 h after the end of vancomycin administration. Pharmacokinetics was analyzed by nonlinear mixed effect modeling.

RESULTS

One hour after vancomycin administration, lung tissue concentrations in the aerosol group were 13 times the concentrations in the intravenous group (median and interquartile range: 161 [71, 301] μg/g versus 12 [4, 42] μg/g; P < 0.0001). Twelve hours after vancomycin administration, lung tissue concentrations in the aerosol group were 63 (23, 119) μg/g and 0 (0, 19) μg/g in the intravenous group (P < 0.0001). A two-compartment weight-scaled allometric model with first-order absorption and elimination best fit serum pharmacokinetics after both routes of administration. Area under the time-concentration curve from 0 to 12 h was lower in the aerosol group in comparison to the intravenous group (56 [8, 70] mg · h · l vs. 121 [103, 149] mg · h · l, P = 0.002). Using a population model, vancomycin bioavailability was 13% (95% CI, 6 to 69; coefficient of variation = 85%) and absorption rate was slow (absorption half life = 0.3 h).

CONCLUSIONS

Administration of vancomycin by nebulization resulted in higher lung tissue concentrations than the intravenous route.

Electrochemical Aptamer-Based Sensors for Improved Therapeutic Drug Monitoring and High-Precision, Feedback-Controlled Drug Delivery

The electrochemical aptamer-based (E-AB) sensing platform appears to be a convenient (rapid, single-step, and calibration-free) and modular approach to measure concentrations of specific molecules (irrespective of their chemical reactivity) directly in blood and even in situ in the living body. Given these attributes, the platform may thus provide significant opportunities to render therapeutic drug monitoring (the clinical practice in which dosing is adjusted in response to plasma drug measurements) as frequent and convenient as the measurement of blood sugar has become for diabetics. The ability to measure arbitrary molecules in the body in real time could even enable closed-loop feedback control over plasma drug levels in a manner analogous to the recently commercialized controlled blood sugar systems. As initial exploration of this, we describe here the selection of an aptamer against vancomycin, a narrow therapeutic window antibiotic for which therapeutic monitoring is a critical part of the standard of care, and its adaptation into an electrochemical aptamer-based (E-AB) sensor. Using this sensor, we then demonstrate: (i) rapid (seconds) and convenient (single-step and calibration-free) measurement of plasma vancomycin in finger-prick-scale samples of whole blood, (ii) high-precision measurement of subject-specific vancomycin pharmacokinetics (in a rat animal model), and (iii) high-precision, closed-loop feedback control over plasma levels of the drug (in a rat animal model). The ability to not only track (with continuous-glucose-monitor-like measurement frequency and convenience) but also actively control plasma drug levels provides an unprecedented route toward improving therapeutic drug monitoring and, more generally, the personalized, high-precision delivery of pharmacological interventions.

Graphene–Gold Nanostructures Hybrid Composites Screen-Printed Electrode for the Sensitive Electrochemical Detection of Vancomycin

The most important and well-known glycopeptide antibiotic, vancomycin (VAN), is used for the treatment of severe bacterial infections like methicillin-resistant staphylococcal infections and endocarditis caused by enterococci and sepsis. Taking into account the problem of the development of antibiotic resistance as well as its toxicity, both correlated with the VAN concentration (CVAN) in biological samples, there is need for better and more accessible quantification methods for this antibiotic. Considering all of the above, herein, we present a simple electrochemical method for VAN sensing based on a hybrid graphene-gold nanostructure nanocomposite electrode, which allows double detection directly in the oxidation domain and also indirectly, in reduction, using the electro-active gold nanostructures as a probe to monitor the current changing due to the interaction between gold and VAN. The developed method was able to successfully detect VAN in the linear range of 1–100 µM with a limit of detection (LOD) of 0.29 µM for the direct approach and 0.5 µM for the indirect one. The selectivity of the method was tested in the presence of other antibiotics and drugs. This method was successfully applied for the detection of VAN from human serum samples.

Characterization and Antibiofilm Activity of Mannitol-Chitosan-Blended Paste for Local Antibiotic Delivery System

Mannitol, a polyalcohol bacterial metabolite, has been shown to activate dormant persister cells within bacterial biofilm. This study sought to evaluate an injectable blend of mannitol, chitosan, and polyethylene glycol for delivery of antibiotics and mannitol for eradication of Staphylococcal biofilm. Mannitol blends were injectable and had decreased dissociation and degradation in the enzyme lysozyme compared to blends without mannitol. Vancomycin and amikacin eluted in a burst response, with active concentrations extended to seven days compared to five days for blends without mannitol. Mannitol eluted from the paste in a burst the first day and continued through Day 4. Eluates from the mannitol pastes with and without antibiotics decreased viability of established S. aureus biofilm by up to 95.5% compared to blends without mannitol, which only decreased biofilm when loaded with antibiotics. Cytocompatibility tests indicated no adverse effects on viability of fibroblasts. In vivo evaluation of inflammatory response revealed mannitol blends scored within the 2–4 range at Week 1 (2.6 ± 1.1) and at Week 4 (3.0 ± 0.8), indicative of moderate inflammation and comparable to non-mannitol pastes (p = 0.065). Clinically, this paste could be loaded with clinician-selected antibiotics and used as an adjunctive therapy for musculoskeletal infection prevention and treatment.

Characterization of trimethyl chitosan/polyethylene glycol derivatized chitosan blend as an injectable and degradable antimicrobial delivery system

Advanced local delivery systems are needed as adjunctive treatments for severe injuries with high infection rates, such as open fractures. Chitosan systems have been investigated as antimicrobial local delivery systems for orthopaedic infection but possess mismatches between elution and degradation properties. Derivatives of chitosan were chosen that have enhanced swelling ratios or tailorable degradation properties. A combination of trimethyl chitosan and poly(ethylene glycol) diacrylate chitosan was developed as an injectable local delivery system. Research objectives were elution of antimicrobials for 7 days, degradation as open fractures heal, and cytocompatibility. The derivative combination eluted increased active concentrations of vancomycin and amikacin compared to the non-derivatized chitosan paste, 6 vs. 5 days and 5 vs. 4 days, respectively. The derivative combination degraded slower than non-derivatized paste in an enzymatic degradation study, 14 vs. 3 days, which increased antimicrobial delivery duration. Cytocompatibility of the combination with fibroblast and pre-osteoblast cells exceeds the cell viability standard set in ISO 10993-5. Combination paste requires an increased ejection force of 9.40 N (vs. 0.64 N), but this force was within an acceptable injection force threshold, 80 N. These preliminary results indicate combination paste should be further developed into a clinically useful adjunctive local delivery system for infection prevention.

Evaluation of vancomycin use in university-affiliated hospitals in Southern Khorasan Province (East Iran) based on HICPAC guidelines

Background

Vancomycin resistance has raised concerns about its effectiveness prospect in the treatment of patients with Gram-positive infections. The Healthcare Infection Control Practices Advisory Committee (HICPAC) has recently established guidelines to delineate improper use of vancomycin. In this light, we sought out to determine the appropriateness of vancomycin prescription using the HICPAC guidelines.

Setting

The study was carried out in two university-affiliated hospitals, Valiasr and Imam Reza, with 297 and 234 beds, respectively, from May 2012 to May 2013.

Methods

This retrospective study evaluated the vancomycin prescription and usage in the hospitals. Total vancomycin use was determined and expressed as vancomycin courses per 298 admitted patients. The patient information was collected on a data collection sheet as follows: demographic variables, etiology and localization of infection, microbiological data, duration of vancomycin treatment, reasons for vancomycin prescription, prescribed antibiotic dosing, and patient regimen.

Results

The average age of the patients and vancomycin treatment duration were 55.965 years and 10.5 days, respectively. Septicemia (15.7%) was the most common cause of vancomycin administration. Vancomycin use was documented to be appropriate and inappropriate in 236 (89.4%) and 28 (10.6%) patients, respectively. No statistically significant differences were found among the wards and hospitals (P values =0.66 and 0.54, respectively) in terms of appropriateness of vancomycin use based on the HICPAC criteria. In addition, 29.21% and 62% of all patients exhibited complete and partial recovery, respectively. We found that 90% of the cases showed compliance with the HICPAC recommendations.

Conclusion

Comprehensive programs are required to improve the vancomycin use in the hospitals. Vancomycin use should be monitored due to its large-scale empiric use. The rate of improper use of vancomycin in the infection and intensive care unit services may be high, and pharmacists must take appropriate action to optimize the use of the drug.

Vancomycin Determination by Disrupting Electron-Transfer in a Fluorescence Turn-On Squaraine-Anthraquinone Triad

A highly sensitive and selective probe for Vancomycin (Van) in aqueous and serum samples is developed in this study. The probe is based on a triad consisting of a near-infrared squaraine dye (Seta-640) conjugated to two anthraquinone molecules via Lys-d-Ala-d-Ala peptides. In the absence of Van, the close proximity and efficient electron-transfer from the excited Seta-640 dye to anthraquinone result in significant fluorescence quenching of the dye ("off"-state). When Van is added, the antibiotic molecules bind with high affinity to the -d-Ala-d-Ala ligands in a 2:1 stoichiometry (Van:triad), resulting in fluorescence recovery that is as high as 30 times ("on"-state). Even though bound Van enhances the fluorescence by reducing the rate of (intrinsic) polarity-induced nonradiative decay process, this effect plays only a minor role. Instead, the main reason behind the observed fluorescence recovery after drug binding is the effective inhibition of electron-transfer; plausibly arising from a steric-induced lengthening of the spatial separation between electron donor and acceptor. The probe has detection limits of 7.0 and 96.9 nM in buffer and human serum, respectively, operates in the clinically relevant range, is insensitive to Van crystalline degradation product (CDP-1), and is easy to operate by using a commonly available fluorescence spectrometer.

A Rapid and Simple HPLC Method for Therapeutic Monitoring of Vancomycin

Therapeutic monitoring of the antibiotic vancomycin is important to achieve specific plasma concentration and prevent toxic effects. Several assays have been described for vancomycin determination in clinical practice, but high-performance liquid chromatography is still considered the gold standard for the quantification of vancomycin. In this study, we developed a new and rapid high-performance liquid chromatography method requiring 50 μL of plasma for the quantification of vancomycin. Acetonitrile was used for processing plasma by protein precipitation (1:2.5). Isocratic chromatographic analysis was carried out on a C18 silica-based (2.7 μm) column with the mobile phase containing 20 mM ammonium acetate/formic acid buffer (pH 4.0):methanol 88:12 (v/v). A diode array detector was used for UV detection at 240 nm. This method was validated according to the Brazilian Health Surveillance Agency legislation and International Conference on Harmonization guidelines. The measurement range was 1-100 μg/mL, analysis time was 8 min, and intermediate precision was <12%, supporting the present method as a fast, simple, and effective alternative for therapeutic monitoring of vancomycin.

High-Performance Liquid Chromatography Method for Rich Pharmacokinetic Sampling Schemes in Translational Rat Toxicity Models With Vancomycin

A translational need exists to understand and predict vancomycin‐induced kidney toxicity. We describe: (i) a vancomycin high‐performance liquid chromatography (HPLC) method for rat plasma and kidney tissue homogenate; (ii) a rat pharmacokinetic (PK) study to demonstrate utility; and (iii) a catheter retention study to enable future preclinical studies. Rat plasma and pup kidney tissue homogenate were analyzed via HPLC for vancomycin concentrations ranging from 3–75 and 15.1–75.5 μg/mL, respectively, using a Kinetex Biphenyl column and gradient elution of water with 0.1% formic acid: acetonitrile (70:30 v/v). Sprague‐Dawley rats (n = 10) receiving 150 mg/kg of vancomycin intraperitoneally had plasma sampled for PK. Finally, a catheter retention study was performed on polyurethane catheters to assess adsorption. Precision was <6.1% for all intra‐assay and interassay HPLC measurements, with >96.3% analyte recovery. A two‐compartment model fit the data well, facilitating PK exposure estimates. Finally, vancomycin was heterogeneously retained by polyurethane catheters.

Sensitive Detection of Staphylococcus aureus with Vancomycin-Conjugated Magnetic Beads as Enrichment Carriers Combined with Flow Cytometry

A novel sandwich strategy was designed to detect Staphylococcus aureus. The strategy is based on an antibacterial agent that captures bacterial cells and a fluorescein-labeled antibody that acts as the signal-output probe. Vancomycin (Van), which exerts a strong antibacterial effect on Gram-positive bacteria, was utilized as a molecular recognition agent to detect pathogenic bacteria. To effectively concentrate S. aureus, we used bovine serum albumin (BSA) as the amplification carrier to modify magnetic beads (MBs), which were then functionalized with Van. To improve the specificity of the method for S. aureus detection, we adopted fluorescein isothiocyanate (FITC)-tagged pig immunoglobulin G (FITC-pig IgG) as the signal probe and the second recognition agent that bound between the Fc fragment of pig IgG and protein A in the surface of S. aureus. To quantify S. aureus, we measured the fluorescence signal by flow cytometry (FCM). The use of multivalent magnetic nanoprobes (Van-BSA-MBs) showed a high concentration efficiency (>98%) at bacterial concentrations of only 33 colony-forming units (CFU)/mL. Furthermore, the sandwich mode (FITC-pig IgG/SA/Van-BSA-MBs) also showed ideal specificity because Van and IgG bound with S. aureus at two distinct sites. The detection limit for S. aureus was 3.3 × 10¹ CFU/mL and the total detection process could be completed within 120 min. Other Gram-positive bacteria and Gram-negative bacteria, including Listeria monocytogenes, Bacillus cereus, Cronobacter sakazakii, Escherichia coli O157:H7, and Salmonella Enteritidis, negligibly interfered with S. aureus detection. The proposed detection strategy for S. aureus possesses attractive characteristics, such as high sensitivity, simple operation, short testing time, and low cost.

An LC-MS/MS method to determine vancomycin in plasma (total and unbound), urine and renal replacement therapy effluent

AIM

Critical illness and medical interventions, such as renal replacement therapy, can cause changes to vancomycin pharmacokinetics and lead to suboptimal dosing. To comprehensively characterize vancomycin pharmacokinetic a method must measure vancomycin in a range of clinical matrices.

RESULTS

A LC-MS/MS method was developed using hydrophilic interaction liquid chromatography and microsample volumes, where possible. For all matrices, the linear concentration range was 1-100 μg/ml, interassay accuracy and precision was within 15%, and recovery above 80%. No matrix effects were observed. Calibration equivalence may be applied for some matrix combinations.

CONCLUSION

A method for the analysis of vancomycin in plasma (total, unbound), urine and renal replacement therapy effluent, suitable for use in any patient pharmacokinetic study, has been developed and validated.

Simple and rapid quantification of vancomycin in serum, urine and peritoneal/pleural effusion via UHPLC-MS/MS applicable to personalized antibiotic dosing research

Management of the therapy of life-threatening bacterial infection is extremely based on an optimal antibiotic treatment. Achieving the correct vancomycin dosage in blood and target tissues can be complicated in special situations, e.g., where large fluid sequestration and/or acute renal failure occur. A UHPLC-MS/MS method operating in electrospray (ESI) positive ion mode was applied for the determination of vancomycin in serum, urine and peritoneal/pleural effusion. Sample pretreatment was composed of dilution and simple protein precipitation where only a small volume (50μL) of serum, urine or peritoneal/pleural effusion was required. The separation of vancomycin was performed on a Meteoric Core C18 BIO column (100×4.6mm, 2.7μm) by gradient elution with 0.1% formic acid in water and acetonitrile. The total time of analysis was 4.5min. The method was found to be linear in the range of 2-60μM (or 0.5-10μM) for serum, 0.27-10μM (or 2-60μM) for peritoneal/pleural effusion and 25-300μM for urine, which was adequate for the determination of vancomycin in patient samples. The intra- and inter-day precision was below 8% RSD, and accuracy was from 89 to 104%. The UHPLC/MS-MS method offers a fast and reliable approach to determine vancomycin concentrations in three different human body fluid samples (serum, urine and peritoneal/pleural effusion) with a simple sample pretreatment that was the same for all selected specimens. This method should be applicable to large sample series in clinical (pharmacokinetic/pharmacodynamic) studies.