Assays for therapeutic drug monitoring of β-lactam antibiotics: A structured review

The New Delhi metallo-β-lactamase-1 biosensor rapidly and accurately detected antibiotic plasma concentrations in cefuroxime-treated patients

OBJECTIVES

Therapeutic drug monitoring (TDM) of β-lactam antibiotics in critically ill patients may benefit dose optimisation, thus improving therapeutic outcomes. However, rapidly and accurately detecting these antibiotics in blood remains a challenge. This research group recently developed a thermometric biosensor called the New Delhi metallo-β-lactamase-1 (NDM-1) biosensor, which detects multiple classes of β-lactam antibiotics in spiked plasma samples.

METHODS

This study assessed the NDM-1 biosensor's effectiveness in detecting plasma concentrations of β-lactam antibiotics in treated patients. Seven patients receiving cefuroxime were studied. Plasma samples collected pre- and post-antibiotic treatment were analysed using the NDM-1 biosensor and compared with liquid chromatography coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).

RESULTS

The biosensor detected plasma samples without dilution, and a brief pre-treatment using a polyvinylidene fluoride filter significantly lowered matrix effects, reducing the running time to 5-8 minutes per sample. The assay's linear range for cefuroxime (6.25-200 mg/L) covered target concentrations during the trough phase of pharmacokinetics in critically ill patients. The pharmacokinetic properties of cefuroxime in treated patients determined by the NDM-1 biosensor and the UPLC-MS/MS were comparable, and the cefuroxime plasma concentrations measured by the two methods showed statistically good consistency.

CONCLUSION

These data demonstrate that the NDM-1 biosensor assay is a fast, sensitive, and accurate method for detecting cefuroxime plasma concentrations in treated patients and highlights the NDM-1 biosensor as a promising tool for on-site TDM of β-lactam antibiotics in critically ill patients.

In vitro stability study of 10 beta-lactam antibiotics in human plasma samples

BACKGROUND AND OBJECTIVES

Beta-lactam antibiotics are reported for some of them to be subject to a rapid degradation in infusion solutions and in human blood samples. However, the current data of stability available in blood samples are limited to a few number of beta-lactam antibiotics, and the methodology of the corresponding studies may be discussed. The objective of the present study is to evaluate the stability of 10 beta-lactam antibiotics in human plasma samples.

METHODS

Stability of amoxicillin, cefazolin, cefepime, cefotaxime, cefoxitin, ceftazidime, ceftriaxone, imipenem, meropenem, and piperacillin was evaluated at low and high concentrations at 20°C, 4°C, -20°C, and -80°C for 1, 7, 60, and 90 days, respectively.

RESULTS

Amoxicillin, cefepime, meropenem, and piperacillin were the least stable antibiotics. The maximum durations allowing the stability for all the evaluated beta-lactams at both tested concentrations were estimated at 3 h, 23 h, 10 days, and 35 days at 20°C, 4°C, -20°C, and -80°C, respectively.

CONCLUSION

We recommend to transport antibiotic plasma samples in ice at 4°C and even at -20°C if these samples come from external hospitals. Ideally, plasma samples should be stored at -80°C if possible; if not, the analysis of the samples should be performed as soon as possible in the limit of 10 days after a storage at -20°C.

A high performance liquid chromatography-tandem mass spectrometry assay for therapeutic drug monitoring of 10 drug compounds commonly used for antimicrobial therapy in plasma and serum of critically ill patients: Method optimization, validation, cross-validation and clinical application

BACKGROUND AND AIMS

Intensive care antibiotic treatment faces challenges due to substantial pharmacokinetic differences in critically ill patients. Individualized antibiotic dosing guided by therapeutic drug monitoring (TDM) is considered to minimize the risk of treatment failure and toxicity. This study aimed to develop a valid method for simultaneous LC-MS/MS quantification of 10 drugs frequently used in intensive care antibiotic therapy for which TDM-guided dosing is recommended: piperacillin, meropenem, flucloxacillin, cefuroxime, vancomycin, colistin A and B, linezolid, ciprofloxacin and tazobactam.

METHODS AND RESULTS

Thorough optimization of sample preparation and chromatography resulted in a fast and simple method based on protein precipitation of 50 µL plasma or serum and gradient elution using an Acquity UPLC HSS-T3 column. Electrospray ionization-triple quadrupole mass spectrometry in dynamic multiple reaction monitoring was used for quantification, covering the therapeutic range of each drug compound. Validation following EMA and FDA recommendations, including inter-platform validation and inter-laboratory comparison, demonstrated high accuracy, precision and robustness of the new method. The assay was successfully used to monitor plasma antibiotic levels of critically ill patients (n = 35).

CONCLUSION

The established multiplex method covers major drug classes with documented dosing challenges, provides a reliable basis for the implementation of high-throughput TDM, and its application confirmed the clinical impact of TDM in a real-world setting.

Liquid chromatography-tandem mass spectrometry methods for quantification of total and free antibiotic concentrations in serum and exudate from patients with post-sternotomy deep sternal wound infection receiving negative pressure wound therapy

BACKGROUND

Systemically administered antibiotics are thought to penetrate the wounds more effectively during negative pressure wound therapy (NPWT).To test this hypothesis total and free antibiotic concentrations were quantified in serum and wound exudate.

METHODS

UHPLC-MS/MS methods were developed and validated for the determination of ceftazidime, cefepime, cefotaxime, cefuroxime, cefazolin, meropenem, oxacillin, piperacillin with tazobactam, clindamycin, ciprofloxacin, sulfamethoxazole/trimethoprim (cotrimoxazole), gentamicin, vancomycin, and linezolid. The unbound antibiotic fraction was obtained by ultrafiltration using a Millipore Microcon-30kda Centrifugal Filter Unit. Analysis was performed on a 1.7-µm Acquity UPLC BEH C18 2.1 × 100-mm column with a gradient elution.

RESULTS

The validation was performed for serum, exudates and free fractions. For all matrices, requirements were met regarding linearity, precision, accuracy, limit of quantitation, and matrix effect. The coefficient of variation was in the range of 1.2-13.6%.and the recovery 87.6-115.6%, respectively. Among the 29 applications of antibiotics thus far, including vancomycin, clindamycin, ciprofloxacin, oxacillin, cefepime, cefotaxime, cotrimoxazole, and gentamicin, total and free antibiotic concentrations in serum and exudate were correlated.

CONCLUSION

This method can accurately quantify the total and free concentrations of 16 antibiotics. Comparison of concentration ratios between serum and exudates allows for monitoring individual antibiotics' penetration capacity in patients receiving NPWT.

Simultaneous determination of oxacillin and cloxacillin in plasma and CSF using turbulent flow liquid chromatography coupled to high-resolution mass spectrometry: Application in therapeutic drug monitoring

Cloxacillin and oxacillin are group M penicillins. The therapeutic monitoring of plasma concentrations of these antibiotics and those of their hydroxymethylated metabolites is of great clinical interest, especially in the choice of an adequate dosage allowing an effective treatment while limiting the occurrence of undesirable effects and the development of bacterial resistance. In this context, we conducted this work aiming at developing and validating a method allowing the determination of cloxacillin and oxacillin as well as the identification of their active metabolites in different biological matrices (CSF and plasma) using turbulent flow liquid chromatography coupled to high-resolution mass spectrometry. To do this, we carried out several optimisation tests. Subsequently, we validated our method according to the latest bioanalytical validation recommendations of the European Medicines Agency. The validation results showed that our method is specific and sensitive. We obtained good linearity in the range 0.5 to 100 µg/mL with correlation coefficients above 0.995. The lower limit of quantification was 0.5 µg/mL for each analyte. The method was found to be accurate with repeatability and reproducibility coefficients of variation below 15 %. Our method is also accurate with bias values below 15 %. Recovery values ranged from 87 % to 95 %. Finally, we were able to apply our method to the therapeutic monitoring of the analysed molecules and to identify their active metabolites. Our results suggest that LC-MS shows superiority in the therapeutic monitoring of these antibiotics due to the superiority of specificity shown by this method. This assay method can be routinely used for the daily plasma assays of patients treated with these antibiotics in the context of therapeutic monitoring.

The clinical application of beta-lactam antibiotic therapeutic drug monitoring in the critical care setting

Critically ill patients have increased variability in beta-lactam antibiotic (beta-lactam) exposure due to alterations in their volume of distribution and elimination. Therapeutic drug monitoring (TDM) of beta-lactams, as a dose optimization and individualization tool, has been recommended to overcome this variability in exposure. Despite its potential benefit, only a few centres worldwide perform beta-lactam TDM. An important reason for the low uptake is that the evidence for clinical benefits of beta-lactam TDM is not well established. TDM also requires the availability of specific infrastructure, knowledge and expertise. Observational studies and systematic reviews have demonstrated that TDM leads to an improvement in achieving target concentrations, a reduction in potentially toxic concentrations and improvement of clinical and microbiological outcomes. However, a small number of randomized controlled trials have not shown a mortality benefit. Opportunities for improved study design are apparent, as existing studies are limited by their inclusion of heterogeneous patient populations, including patients that may not even have infection, small sample size, variability in the types of beta-lactams included, infections caused by highly susceptible bacteria, and varied sampling, analytical and dosing algorithm methods. Here we review the fundamentals of beta-lactam TDM in critically ill patients, the existing clinical evidence and the practical aspects involved in beta-lactam TDM implementation.

Developing a Method for Quantifying Meropenem in Children-Volumetric Adsorptive Microsampling Versus Plasma Sampling

BACKGROUND

Meropenem is a carbapenem antibiotic often used in pediatric intensive care units due to its broad spectrum of activity. Therapeutic drug monitoring (TDM) is a useful tool to increase the effectiveness of meropenem by adjusting the dose based on plasma levels; however, the relatively large sample volume required for TDM can limit its use in children. Therefore, this study aimed to determine meropenem concentrations and consequently perform TDM effectively using the smallest possible sample volume. Volumetric absorptive microsampling (VAMS) is a sampling technology developed to collect a small, precise volume of blood. For the applicability of VAMS in TDM, plasma concentrations must be reliably calculated from whole blood (WB) collected by VAMS.

METHODS

VAMS technology using 10 µL of WB was evaluated and compared with EDTA-plasma sampling. High-performance liquid chromatography with UV detection was applied to quantify meropenem in VAMS and plasma samples after the removal of proteins by precipitation. Ertapenem was used as the internal standard. Samples were collected simultaneously from critically ill children receiving meropenem using VAMS and traditional sampling.

RESULTS

It was found that no consistent factor could be determined to calculate meropenem plasma concentrations from the WB, indicating that VAMS was not reliable in the TDM of meropenem. Therefore, to reduce the required sample amount in pediatric patients, a method for quantifying meropenem from 50 µL of plasma with a lower limit of quantification of 1 mg/L was developed and successfully validated.

CONCLUSIONS

A simple, reliable, and low-cost method was established using high-performance liquid chromatography-UV to determine the concentration of meropenem in 50 µL of plasma. VAMS using WB does not seem to be suitable for TDM of meropenem.

Development and Validation of a Strong Cation Exchange Chromatographic Column Coupled with High-Performance Liquid Chromatography Method for Meropenem and Evaluation of Its Stability in Human Plasma: Application to the Therapeutic Drug Monitoring

Meropenem is a wide inter-individual variability in the pharmacokinetic, and standard dosing may not be adequate in critically ill patients. Therapeutic drug monitoring is a useful tool to optimize dosing. Meropenem is the amphoteric compound with an isoelectric point of 5.15. The secondary amino group of meropenem is positively charged when pH ≤ 5.4, thus we attempted to separate by strong cation exchange (SCX) column using acetonitrile/25-mM potassium dihydrogen phosphate (pH 3.0; 60:40) as mobile phase, and good peak shape and effective separation obtained. Generally, meropenem were unstable in plasma. We try to investigate stability of plasma samples using the medium QC sample with or without 3-(N-morpholino) propanesulfonic acid (MOPS) as stabilizer solutions at possible conditions during handling and storage. Meropenem showed higher stability at -80°C, and addition of MOPS might increase the short-term and extracted samples stability. This method is suitable for the quantification of meropenem in human plasma from 0.5 to 100 μg/mL. The accuracy was ranged from 96.53 to 101.11% with relative standard deviation ≤ 4.76%. The method has been used for determined 63 critically ill patients treated with meropenem. During the first measurement, 11 patients showed trough levels below the target ranges despite standard dosing. Through continuous or prolonged infusion, 8/11 patients (72.73%) led to adequate trough levels. The described SCX-high-performance liquid chromatography method for meropenem in human plasma is a powerful tool for therapeutic drug monitoring.

Therapeutic drug monitoring of carbapenem antibiotics in critically ill patients: an overview of principles, recommended dosing regimens, and clinical outcomes

INTRODUCTION

The importance of antibiotic treatment for sepsis in critically ill septic patients is well established. Consistently achieving the dose of antibiotics required to optimally kill bacteria, minimize the development of resistance, and avoid toxicity is challenging. The increasing understanding of the pharmacokinetic and pharmacodynamic (PK/PD) characteristics of antibiotics, and the effects of critical illness on key PK/PD parameters, is gradually re-shaping how antibiotics are dosed in critically ill patients.

AREAS COVERED

The PK/PD characteristics of commonly used carbapenem antibiotics, the principles of the application of therapeutic drug monitoring (TDM), and current as well as future methods of utilizing TDM to optimally devise dosing regimens will be reviewed. The limitations and evidence-base supporting the use of carbapenem TDM to improve outcomes in critically ill patients will be examined.

EXPERT OPINION

It is important to understand the principles of TDM in order to correctly inform dosing regimens. Although the concept of TDM is attractive, and the ability to utilize PK software to optimize dosing in the near future is expected to rapidly increase clinicians' ability to meet pre-defined PK/PD targets more accurately, current evidence provides only limited support for the use of TDM to guide carbapenem dosing in critically ill patients.

Skin-Interfaced Wearable Sweat Sensors for Precision Medicine

Wearable sensors hold great potential in empowering personalized health monitoring, predictive analytics, and timely intervention toward personalized healthcare. Advances in flexible electronics, materials science, and electrochemistry have spurred the development of wearable sweat sensors that enable the continuous and noninvasive screening of analytes indicative of health status. Existing major challenges in wearable sensors include: improving the sweat extraction and sweat sensing capabilities, improving the form factor of the wearable device for minimal discomfort and reliable measurements when worn, and understanding the clinical value of sweat analytes toward biomarker discovery. This review provides a comprehensive review of wearable sweat sensors and outlines state-of-the-art technologies and research that strive to bridge these gaps. The physiology of sweat, materials, biosensing mechanisms and advances, and approaches for sweat induction and sampling are introduced. Additionally, design considerations for the system-level development of wearable sweat sensing devices, spanning from strategies for prolonged sweat extraction to efficient powering of wearables, are discussed. Furthermore, the applications, data analytics, commercialization efforts, challenges, and prospects of wearable sweat sensors for precision medicine are discussed.

Determination of the microscopic acid dissociation constant of piperacillin and identification of dissociated molecular forms

For amphoteric ß-lactam antibiotics, the acid dissociation constant (pK a) is a fundamental parameter to characterize physicochemical and biochemical properties of antibiotics and to predict persistence and removal of drugs. pK a of piperacillin (PIP) is determined by potentiometric titration with a glass electrode. Electrospray ionization mass spectrometry (ESI-MS) is creatively applied to verify the reasonable pK a value at every dissociation step. Two microscopic pK a values (3.37 ± 0.06 and 8.96 ± 0.10) are identified and attributed to the direct dissociation of the carboxylic acid functional group and one secondary amide group, respectively. Different from other ß-lactam antibiotics, PIP presents a dissociation pattern where direct dissociation is involved instead of protonation dissociation. Moreover, the degradation tendency of PIP in an alkaline solution may alter the dissociation pattern or dismiss the corresponding pK a of the amphoteric ß-lactam antibiotics. This work offers a reliable determination of the acid dissociation constant of PIP and a clear interpretation of the effect of stability of antibiotics on the dissociation process.

Update on Therapeutic Drug Monitoring of Beta-Lactam Antibiotics in Critically Ill Patients—A Narrative Review

Beta-lactam antibiotics remain one of the most preferred groups of antibiotics in critical care due to their excellent safety profiles and their activity against a wide spectrum of pathogens. The cornerstone of appropriate therapy with beta-lactams is to achieve an adequate plasmatic concentration of a given antibiotic, which is derived primarily from the minimum inhibitory concentration (MIC) of the specific pathogen. In a critically ill patient, the plasmatic levels of drugs could be affected by many significant changes in the patient’s physiology, such as hypoalbuminemia, endothelial dysfunction with the leakage of intravascular fluid into interstitial space and acute kidney injury. Predicting antibiotic concentration from models based on non-critically ill populations may be misleading. Therapeutic drug monitoring (TDM) has been shown to be effective in achieving adequate concentrations of many drugs, including beta-lactam antibiotics. Reliable methods, such as high-performance liquid chromatography, provide the accurate testing of a wide range of beta-lactam antibiotics. Long turnaround times remain the main drawback limiting their widespread use, although progress has been made recently in the implementation of different novel methods of antibiotic testing. However, whether the TDM approach can effectively improve clinically relevant patient outcomes must be proved in future clinical trials.

Hypoalbuminemia and Pharmacokinetics: When the Misunderstanding of a Fundamental Concept Leads to Repeated Errors over Decades

Surprisingly, misinterpretation of the influence of hypoalbuminemia on pharmacokinetics and the clinical effects of drugs seems to be a current problem, even though hypoalbuminemia has no impact on the pharmacologically active exposure. Exceptions to this fact are highly protein-bound anaesthetics with high elimination capacity (i.e., <5 drugs on the market). To assess the frequency of misinterpretation of the influence of hypoalbuminemia on pharmacokinetics and the clinical effects of drugs between 1975 and 2021, a PubMed literature review was conducted. Each paragraph on albumin binding was classified as correct, ambiguous or incorrect, creating two acceptable categories: (1) content without any errors, and (2) content containing some incorrect and/or ambiguous statements. The analyses of these articles showed that fewer than 11% of articles contained no interpretation errors. In order to contain this misinterpretation, several measures are proposed: (1) Make the message accessible to a wide audience by offering a simplified and didactic video representation of the lack of impact of albumin binding to drugs. (2) Precise terminology (unbound/free form/concentration) should be used for highly bound drugs. (3) Unbound/free forms should be systematically quantified for highly plasma protein bound drugs for clinical trials as well as for therapeutic drug monitoring.

Simple HPLC-UV Method for Piperacillin/Tazobactam Assay in Human Plasma

BACKGROUND

Piperacillin (Pip)/tazobactam (Taz) is a broad-spectrum antimicrobial agent that has been commonly used in the intensive care unit for severe and life-threatening infections. Recent evidence suggests that therapeutic drug monitoring (TDM) for Pip could be beneficial in clinical practice to facilitate dose optimization and increase the odds of treatment success. The aim was to develop and validate a sensitive and simple high-performance liquid chromatography (HPLC) method for the simultaneous quantification of Pip and Taz in human plasma.

METHODS

Samples (0.3 mL) were deproteinized with acetonitrile. The supernatant was evaporated and then reconstituted and injected into the HPLC. The chromatographic analysis was carried out by using the C18 column and gradient elution with the acetonitrile:water mobile phase mixture with 0.1% trifluoracetic acid at a flow rate of 0.8 mL/min using a UV detector at 218 nm.

RESULTS

The method had acceptable linearity (r² > 0.99) over the concentration ranges of 0.5-400 μg/mL and 1-100 μg/mL for Pip and Taz, respectively. The method demonstrated acceptable inter- and intra-day precision and accuracy within ±20% with adequate stability results.

CONCLUSION

The developed method is sensitive and simple and utilizes simple sample preparation and elution steps, making it suitable and practical for Pip/Taz TDM.

β-Lactam Dosing in Critical Patients: A Narrative Review of Optimal Efficacy and the Prevention of Resistance and Toxicity

Antimicrobial prescription in critically ill patients represents a complex challenge due to the difficult balance between infection treatment and toxicity prevention. Underexposure to antibiotics and therapeutic failure or, conversely, drug overexposure and toxicity may both contribute to a worse prognosis. Moreover, changes in organ perfusion and dysfunction often lead to unpredictable pharmacokinetics. In critically ill patients, interindividual and intraindividual real-time β-lactam antibiotic dose adjustments according to the patient's condition are critical. The continuous infusion of β-lactams and the therapeutic monitoring of their concentration have both been proposed to improve their efficacy, but strong data to support their use are still lacking. The knowledge of the pharmacokinetic/pharmacodynamic targets is poor and is mostly based on observational data. In patients with renal or hepatic failure, selecting the right dose is even more tricky due to changes in drug clearance, distribution, and the use of extracorporeal circuits. Intermittent usage may further increase the dosing conundrum. Recent data have emerged linking overexposure to β-lactams to central nervous system toxicity, mitochondrial recovery delay, and microbiome changes. In addition, it is well recognized that β-lactam exposure facilitates resistance selection and that correct dosing can help to overcome it. In this review, we discuss recent data regarding real-time β-lactam antibiotic dose adjustment, options in special populations, and the impacts on mitochondria and the microbiome.

Preanalytical Stability of Flucloxacillin, Piperacillin, Tazobactam, Meropenem, Cefalexin, Cefazolin, and Ceftazidime in Therapeutic Drug Monitoring: A Structured Review

BACKGROUND

Therapeutic drug monitoring is increasingly being used to optimize beta-lactam antibiotic dosing. Because beta-lactams are inherently unstable, confirming preanalytical sample stability is critical for reporting reliable results. This review aimed to summarize the published literature on the preanalytical stability of selected widely prescribed beta-lactams used in therapeutic drug monitoring.

METHODS

The published literature (2010-2020) on the preanalytical stability of flucloxacillin, piperacillin, tazobactam, meropenem, cefalexin, cefazolin, and ceftazidime in human plasma, serum, and whole blood was reviewed. Articles examining preanalytical stability at room temperature, refrigerated, or frozen (-20°C) using liquid chromatography with mass spectrometry or ultraviolet detection were included.

RESULTS

Summarizing the available data allowed for general observations to be made, although data were conflicting in some cases (piperacillin, tazobactam, ceftazidime, and meropenem at room temperature, refrigerated, or -20°C) or limited (cefalexin, cefazolin, and flucloxacillin at -20°C). Overall, with the exception of the more stable cefazolin, preanalytical instability was observed after 6-12 hours at room temperature, 2-3 days when refrigerated, and 1-3 weeks when frozen at -20°C. In all cases, excellent stability was detected at -70°C. Studies focusing on preanalytical stability reported poorer stability than studies investigating stability as part of method validation.

CONCLUSIONS

Based on this review, as general guidance, clinical samples for beta-lactam analysis should be refrigerated and analyzed within 2 days or frozen at -20°C and analyzed within 1 week. For longer storage times, freezing at -70°C was required to ensure sample stability. This review highlights the importance of conducting well-designed preanalytical stability studies on beta-lactams and other potentially unstable drugs under clinically relevant conditions.

Development and evaluation of uncertainty quantifying machine learning models to predict piperacillin plasma concentrations in critically ill patients

BACKGROUND

Beta-lactam antimicrobial concentrations are frequently suboptimal in critically ill patients. Population pharmacokinetic (PopPK) modeling is the golden standard to predict drug concentrations. However, currently available PopPK models often lack predictive accuracy, making them less suited to guide dosing regimen adaptations. Furthermore, many currently developed models for clinical applications often lack uncertainty quantification. We, therefore, aimed to develop machine learning (ML) models for the prediction of piperacillin plasma concentrations while also providing uncertainty quantification with the aim of clinical practice.

METHODS

Blood samples for piperacillin analysis were prospectively collected from critically ill patients receiving continuous infusion of piperacillin/tazobactam. Interpretable ML models for the prediction of piperacillin concentrations were designed using CatBoost and Gaussian processes. Distribution-based Uncertainty Quantification was added to the CatBoost model using a proposed Quantile Ensemble method, useable for any model optimizing a quantile function. These models are subsequently evaluated using the distribution coverage error, a proposed interpretable uncertainty quantification calibration metric. Development and internal evaluation of the ML models were performed on the Ghent University Hospital database (752 piperacillin concentrations from 282 patients). Ensuing, ML models were compared with a published PopPK model on a database from the University Medical Centre of Groningen where a different dosing regimen is used (46 piperacillin concentrations from 15 patients.).

RESULTS

The best performing model was the Catboost model with an RMSE and [Formula: see text] of 31.94-0.64 and 33.53-0.60 for internal evaluation with and without previous concentration. Furthermore, the results prove the added value of the proposed Quantile Ensemble model in providing clinically useful individualized uncertainty predictions and show the limits of homoscedastic methods like Gaussian Processes in clinical applications.

CONCLUSIONS

Our results show that ML models can consistently estimate piperacillin concentrations with acceptable and high predictive accuracy when identical dosing regimens as in the training data are used while providing highly relevant uncertainty predictions. However, generalization capabilities to other dosing schemes are limited. Notwithstanding, incorporating ML models in therapeutic drug monitoring programs seems definitely promising and the current work provides a basis for validating the model in clinical practice.

Implementation of a β-lactam therapeutic drug monitoring program: Experience from a large academic medical center

DISCLAIMER

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

To describe the implementation and operationalization of a β-lactam (BL) therapeutic drug monitoring(TDM) program at a large academic center.

SUMMARY

BLs are the most used class of antibiotics. Suboptimal antibiotic exposure is a significant concern in hospitalized patients, particularly in those with altered pharmacokinetics. BL-TDM provides clinicians the opportunity to optimize drug concentrations to ensure maximal therapeutic efficacy while minimizing toxicity. However, BL-TDM has not been widely adopted due to the lack of access to assays. The University of Florida Shands Hospital developed a BL-TDM program in 2015. This is a consultative service primarily run by pharmacists and is conducted in all patient care areas. An analysis was performed on the first BL-TDM encounter for 1,438 patients. BL-TDM was most frequently performed for cefepime (61%, n = 882), piperacillin (15%, n = 218), and meropenem (11%, n = 151). BL-TDM was performed a median of 3 days (interquartile range, 1-5 days) from BL initiation. Among patients with available minimum inhibitory concentration (MIC) values and trough concentrations, the pharmacokinetic/pharmacodynamic (PK/PD) target of 100% fT>MIC was attained in 308 patients (88%). BL-TDM resulted in a dosage adjustment in 25% (n = 361) of patients.

CONCLUSION

Implementation of a BL-TDM program requires the concerted efforts of physicians, pharmacists, nursing staff, phlebotomists, and personnel in the analytical laboratory. Standard antibiotic dosing failed to achieve optimal PK/PD targets in all patients; utilizing BL-TDM, dose adjustments were made in 1 of every 4 patients.

The Role of Surface Enhanced Raman Scattering for Therapeutic Drug Monitoring of Antimicrobial Agents

The rapid quantification of antimicrobial agents is important for therapeutic drug monitoring (TDM), enabling personalized dosing schemes in critically ill patients. Highly sophisticated TDM technology is becoming available, but its implementation in hospitals is still limited. Among the various proposed techniques, surface-enhanced Raman scattering (SERS) stands out as one of the more interesting due to its extremely high sensitivity, rapidity, and fingerprinting capabilities. Here, we present a comprehensive review of various SERS-based novel approaches applied for direct and indirect detection and quantification of antibiotic, antifungal, and antituberculosis drugs in different matrices, particularly focusing on the challenges for successful exploitation of this technique in the development of assays for point-of-care tests.

Dried Plasma Spot Based LC-MS/MS Method for Monitoring of Meropenem in the Blood of Treated Patients

Meropenem (MER) is widely used to treat complicated and serious infections. Therapeutic drug monitoring (TDM) provides a valid clinical tool to avoid suboptimal concentrations and dose−related adverse reactions. However, TDM seems to face challenges since the limited stability of MER in plasma makes transport difficult between clinics and laboratories. Dried plasma spot (DPS) sampling is an attractive but underutilized method for TDM that has the desired features of easy collection, storage, and transport, and overcomes known hematocrit (HCT) issues in dried blood spot (DBS) analysis. This study was designed to investigate a DPS−based liquid chromatography−tandem mass spectrometry (LC−MS/MS) method for quantification of MER. The method was developed and validated for DPS and wet plasma samples. Calibration curves were linear (R2 > 0.995) over the concentration range of 0.5−50 µg/mL. Overall accuracy and precision did not exceed 15% and no significant matrix effect was observed. MER has been more stable in DPS than in wet plasma samples. A comparison of DPS and wet plasma concentrations was assessed in 32 patients treated with MER. The results showed that there was no significant difference between the two methods. So the DPS method developed in this study is appropriate and practical for the monitor of MER in the daily clinical laboratory practice.

Therapeutic Drug Monitoring of Antibiotic Drugs: The Role of the Clinical Laboratory

BACKGROUND

Therapeutic drug monitoring (TDM) of anti-infective drugs is an increasingly complex field, given that in addition to the patient and drug as 2 usual determinants, its success is driven by the pathogen. Pharmacodynamics is related both to the patient (toxicity) and bacterium (efficacy or antibiotic susceptibility). The specifics of TDM of antimicrobial drugs stress the need for multidisciplinary knowledge and expertise, as in any other field. The role and the responsibility of the laboratory in this interplay are both central and multifaceted. This narrative review highlights the role of the clinical laboratory in the TDM process.

METHODS

A literature search was conducted in PubMed and Google Scholar, focusing on the past 5 years (studies published since 2016) to limit redundancy with previously published review articles. Furthermore, the references cited in identified publications of interest were screened for additional relevant studies and articles.

RESULTS

The authors addressed microbiological methods to determine antibiotic susceptibility, immunochemical and chromatographic methods to measure drug concentrations (primarily in blood samples), and endogenous clinical laboratory biomarkers to monitor treatment efficacy and toxicity. The advantages and disadvantages of these methods are critically discussed, along with existing gaps and future perspectives on strategies to provide clinicians with as reliable and useful results as possible.

CONCLUSIONS

Although interest in the field has been the driver for certain progress in analytical technology and quality in recent years, laboratory professionals and commercial providers persistently encounter numerous unresolved challenges. The main tasks that need tackling include broadly and continuously available, easily operated, and cost-effective tests that offer short turnaround times, combined with reliable and easy-to-interpret results. Various fields of research are currently addressing these features.

Quantification of Antibiotics in Patient Samples: State of the Art in Standardization and Proficiency Testing

BACKGROUND

For many antibiotics, the convenient one-fits-all dosing regimen had to be abandoned. Owing to highly variable pharmacokinetics, therapeutic drug monitoring has become an indispensable prerequisite. It is based on a suitable measuring method, sample materials, and standardization. Appropriate quality control including external quality assessment (EQA) is essential. For many antibiotics, EQAs have been established for many decades, whereas others have only lately been introduced. This article gives an insight into the state of the art regarding the therapeutic drug monitoring of antibiotics regarding standardization, EQAs, and reference measurement procedures (RMPs).

METHODS

An overview of the currently available international EQA schemes for antibiotics and a literature overview of available RMPs are given. EQAs including gentamicin and vancomycin have been offered by German providers for more than 25 years. The period 2000-2020 was selected for a detailed analysis. The experiences with a new EQA including linezolid, meropenem, and piperacillin are described.

RESULTS

EQAs for gentamicin and vancomycin are provided in many countries. Those for linezolid, meropenem, and piperacillin do not seem to be very common. Most of the antibiotics monitored for decades are measured by commercially available assays. EQAs for linezolid, meropenem, and piperacillin introduced in 2018 were rapidly accepted in Germany. Methods reported in this study were HPLC based either with UV or mass spectrometric detection. The number of participants succeeding was comparable between UV and mass spectrometry. Candidate RMPs for gentamicin, vancomycin, and linezolid based on isotope dilution mass spectrometry were published.

CONCLUSIONS

EQAs are offered regularly for many antibiotics worldwide. The results of EQAs in Germany generally compare well, but there is potential for improvement. Both immunoassays and HPLC-based methods work properly in EQAs evaluated in Germany. From a quality control perspective, fast and inexpensive methods may be selected without endangering the patient's health based on clinical needs.

OUP accepted manuscript

Objectives

To describe the therapeutic drug monitoring (TDM) of cefepime in non-critically ill adults and compare four different ways of dosing: conventional table-based; empirically adjusted following TDM; individualized based on a population pharmacokinetic (PopPK) model without TDM; and TDM-adjusted with a Bayesian approach integrating TDM and PopPK.

Methods

We conducted a retrospective study in a tertiary centre to examine the current practice of TDM and to evaluate the potential for improvement by PopPK-based software individualization. The prediction of trough concentrations and the total daily doses (TDD) prescribed according to each approach were compared by calculating the mean logarithmic bias and the root mean squared error, complemented by linear regression and variance analysis.

Results

Among 168 trough concentrations in 119 patients (median: 12 mg/L), 38.6% of measurements exceeded 15 mg/L, the reported threshold for neurotoxicity. Nine patients developed neurotoxicity. The prediction performance of PopPK alone for trough concentrations was moderate, but clearly improved after integration of TDM. Accordingly, TDD were significantly lower for a priori PopPK-based dosage (mean: 2907 mg/24 h) compared with actual table-based dosage (4625 mg/24 h, P < 0.001). They were also lower for a posteriori dosage based on PopPK and TDM (3377 mg/24 h) compared with actual dosage after empirical TDM (4233 mg/24 h, P < 0.001), as model-based adjustment privileged more frequent administrations.

Conclusions

Our observations support routine TDM of cefepime to prevent overdosing and subsequent toxicity in the non-critically ill. Software-based individualization seems promising to optimize the benefits of TDM, but has little potential to replace it.

An UPLC-PDA assay for simultaneous determination of seven antibiotics in human plasma

Appropriate antibiotic dosing in critically ill patients requires concentration monitoring due to the occurrence of pathophysiological changes and frequent extracorporeal therapy that could significantly alter the normal pharmacokinetics of drugs. Herein, we describe an ultra-performance liquid chromatography with photodiode array (UPLC-PDA) for the simultaneous concentration determination of seven frequently used antibiotics (meropenem, cefotaxime, cefoperazone, piperacillin, linezolid, moxifloxacin, and tigecycline) in plasma from critically ill patients. The analytes were extracted from 200 μL human plasma by the addition of methanol for protein precipitation. The chromatographic separation was achieved using an ACQUITY UPLC HSS T3 column (2.1 × 50 mm, 1.8 µm) with a water (containing 0.1% trifluoroacetic acid)/acetonitrile linear gradient at a flow rate of 0.5 mL/min in a 4.5 min turn-around time. PDA detection wavelength was set individually for the analytes. The method was fully validated according to the European Medicines Agency (EMA) guideline. The lower limits of quantification for the analytes were between 0.05 and 0.8 μg/mL. The method is accurate (intra/inter-assay bias -8.4 to +12.4%) and precise (intra/inter-assay coefficient of variations 0.9-10.1%) over the clinically relevant plasma concentration ranges (upper limits of quantification 5-400 µg/mL). The applicability of the method has been successfully demonstrated by analyzing plasma samples collected from critically ill patients undergoing continuous renal replacement therapy.

Population Pharmacokinetics of Intravenous Amoxicillin Combined With Clavulanic Acid in Healthy and Critically Ill Dogs

Background: Data regarding antimicrobial pharmacokinetics (PK) in critically ill dogs are lacking and likely differ from those of healthy dogs. The aim of this work is to describe a population PK model for intravenous (IV) amoxicillin–clavulanic acid (AMC) in both healthy and sick dogs and to simulate a range of clinical dosing scenarios to compute PK/PD cutoffs for both populations.

Methods: This study used a prospective clinical trial in normal and critically ill dogs. Twelve client-owned dogs hospitalized in the intensive care unit (ICU) received IV AMC 20 mg/kg every 8 h (0.5-h infusion) during at least 48 h. Eight blood samples were collected at predetermined times, including four trough samples before the next administration. Clinical covariates and outcome were recorded, including survival to discharge and bacteriologic clinical failure. Satellite PK data were obtained de novo from a group of 12 healthy research dogs that were dosed with a single AMC 20 mg/kg IV. Non-linear mixed-effects model was used to estimate the PK parameters (and the effect of health upon them) together with variability within and between subjects. Monte Carlo simulations were performed with seven dosage regimens (standard and increased doses). The correlation between model-derived drug exposure and clinical covariates was tested with Spearman's non-parametric correlation analysis. Outcome was recorded including survival to discharge and bacteriologic clinical failure.

Results: A total of 218 amoxicillin concentrations in plasma were available for healthy and sick dogs. A tricompartmental model best described the data. Amoxicillin clearance was reduced by 56% in sick dogs (0.147 L/kg/h) compared with healthy dogs (0.336 L/kg/h); intercompartmental clearance was also decreased (p <0.01). None of the clinical data covariates were significantly correlated with individual exposure. Monte Carlo simulations showed that higher PK/PD cutoff values of 8 mg/L could be reached in sick dogs by extending the infusion to 3 h or doubling the dose.

Conclusions: The PK of AMC is profoundly different in critically ill dogs compared with normal dogs, with much higher interindividual variability and a lower systemic clearance. Our study allows to generate hypotheses with regard to higher AMC exposure in clinical dogs and provides supporting data to revise current AMC clinical breakpoint for IV administration.

Rapid Detection of Multiple Classes of β-Lactam Antibiotics in Blood Using an NDM-1 Biosensing Assay

Currently, assays for rapid therapeutic drug monitoring (TDM) of β-lactam antibiotics in blood, which might be of benefit in optimizing doses for treatment of critically ill patients, remain challenging. Previously, we developed an assay for determining the penicillin-class antibiotics in blood using a thermometric penicillinase biosensor. The assay eliminates sample pretreatment, which makes it possible to perform semicontinuous penicillin determinations in blood. However, penicillinase has a narrow substrate specificity, which makes it unsuitable for detecting other classes of β-lactam antibiotics, such as cephalosporins and carbapenems. In order to assay these classes of clinically useful antibiotics, a novel biosensor was developed using New Delhi metallo-β-lactamase-1 (NDM-1) as the biological recognition layer. NDM-1 has a broad specificity range and is capable of hydrolyzing all classes of β-lactam antibiotics in high efficacy with the exception of monobactams. In this study, we demonstrated that the NDM-1 biosensor was able to quantify multiple classes of β-lactam antibiotics in blood plasma at concentrations ranging from 6.25 mg/L or 12.5 mg/L to 200 mg/L, which covered the therapeutic concentration windows of the tested antibiotics used to treat critically ill patients. The detection of ceftazidime and meropenem was not affected by the presence of the β-lactamase inhibitors avibactam and vaborbactam, respectively. Furthermore, both free and protein-bound β-lactams present in the antibiotic-spiked plasma samples were detected by the NDM-1 biosensor. These results indicated that the NDM-1 biosensor is a promising technique for rapid TDM of total β-lactam antibiotics present in the blood of critically ill patients.

Next-Generation Digital Biomarkers for Tuberculosis and Antibiotic Stewardship: Perspective on Novel Molecular Digital Biomarkers in Sweat, Saliva, and Exhaled Breath

The internet of health care things enables a remote connection between health care professionals and patients wearing smart biosensors. Wearable smart devices are potentially affordable, sensitive, specific, user-friendly, rapid, robust, lab-independent, and deliverable to the end user for point-of-care testing. The datasets derived from these devices are known as digital biomarkers. They represent a novel patient-centered approach to collecting longitudinal, context-derived health insights. Adding automated, analytical smartphone applications will enable their use in high-, middle-, and low-income countries. So far, digital biomarkers have been focused primarily on accelerometer data and heart rate due to well-established sensors originating from the consumer market. Novel emerging smart biosensors will detect biomarkers (or compounds) independent of a lab and noninvasively in sweat, saliva, and exhaled breath. These molecular digital biomarkers are a promising novel approach to reduce the burden from 2 major infectious diseases with urgent unmet needs: tuberculosis and infections with multidrug resistant pathogens. Active tuberculosis (aTbc) is one of the deadliest diseases from an infectious agent. However, a simple and reliable test for its detection is still missing. Furthermore, inappropriate antimicrobial use leads to the development of antimicrobial resistance, which is associated with high mortality and health care costs. From this perspective, we discuss the innovative approach of a noninvasive and lab-independent collection of novel biomarkers to detect aTbc, which at the same time may additionally serve as a scalable therapeutic drug monitoring approach for antibiotics. These molecular digital biomarkers are next-generation digital biomarkers and have the potential to shape the future of infectious diseases.

Antibiotic resistance and antibiotic-resistance genes of Pseudomonas spp. and Escherichia coli isolated from untreated hospital wastewater

Hospitals are considered an important factor in the spread of antibiotic-resistant bacteria (ARBs) and antibiotic-resistance genes (ARGs). The purpose of this research was to characterize the microbial populations in hospital wastewater and investigated the prevalence of β-lactamase, SulІ and QnrS resistance genes. In the first step, culture method was used to isolate Pseudomonas aeruginosa and Escherichia coli. In the next step, accurate identification of isolated bacteria was carried out using the polymerase chain reaction (PCR) method, then the resistance of the bacteria at different concentrations of antibiotics (8-128 μg/mL) was examined. Finally the ARGs were detected using the PCR method. The averages of heterotrophic plate count (HPC) and ARB concentration in wastewater samples were 1.8 × 10⁸ and 4.3 × 10⁶ CFU/100 mL, respectively. The highest resistance rates were found for sulfamethoxazole and the highest resistance rates in the β-lactamase group were for ceftazidime, while highest sensitivity was for gentamicin and there was no isolate that was sensitive to the studied antibiotics. SulІ and QnrS were the highest and lowest abundance of all ARGs in samples respectively and blaSHV was the highest β-lactam resistance gene. Our results indicated an increase in the resistance of identified bacteria to several antibiotics. So it can be concluded that numerous antibiotic-resistant pathogens and vast numbers of ARGs exist in the human body so that their release from hospitals without effective treatment can cause many dangers to the environment and human health.

In Silico Characterization of the Interaction between the PBP2a "Decoy" Protein of Resistant Staphylococcus aureus and the Monomeric Units of Eudragit E-100 and Poly(Maleic Acid-alt-Octadecene) Polymers

Antimicrobial treatment alternatives for methicillin-resistant Staphylococcus aureus (MRSA) are increasingly limited. MRSA strains are resistant to methicillin due to the formation of β-lactamase enzymes, as well as the acquisition of the mecA gene, which encodes the penicillin-binding protein (PBP2a) that reduces the affinity for β-lactam drugs. Previous studies have shown that the use of ampicillin-loaded nanoparticles can improve antimicrobial activity on resistant S. aureus strains. However, the biological mechanism of this effect has not yet been properly elucidated. Therefore, this short communication focused on characterizing the in silico interactions of the PBP2a membrane receptor protein from S. aureus against the monomeric units of two polymeric materials previously used in the development of different nanoparticles loaded with ampicillin. Such polymers correspond to Eudragit E-100 chloride (EuCl) and the sodium salt of poly(maleic acid-alt-octadecene) (PAM-18Na). For this, molecular coupling studies were carried out in the active site of the PBP2a protein with the monomeric units of both polymers in neutral and ionized form, as well as with ampicillin antibiotic (model β-lactam drug). The results showed that ampicillin, as well as the monomeric units of EuCl and PAM18Na, described a slight binding free energy to the PBPa2 protein. In addition, it was found that the amino acids of the active site of the PBPa2 protein have interactions of different types and intensities, suggesting, in turn, different forms of protein–substrate coupling.

Optimization of flucloxacillin dosing regimens in critically ill patients using population pharmacokinetic modelling of total and unbound concentrations

Background

Initial appropriate anti-infective therapy is associated with improved outcomes in patients with severe infections. In critically ill patients, altered pharmacokinetic (PK) behaviour is common and known to influence the achievement of PK/pharmacodynamic targets.

Objectives

To describe population PK and optimized dosing regimens for flucloxacillin in critically ill patients.

Methods

First, we developed a population PK model, estimated between-patient variability (BPV) and identified covariates that could explain BPV through non-linear mixed-effects analysis, using total and unbound concentrations obtained from 35 adult critically ill patients treated with intermittent flucloxacillin. Second, we validated the model using external datasets from two different countries. Finally, frequently prescribed dosing regimens were evaluated using Monte Carlo simulations.

Results

A two-compartment model with non-linear protein binding was developed and validated. BPV of the maximum binding capacity decreased from 42.2% to 30.4% and BPV of unbound clearance decreased from 88.1% to 71.6% upon inclusion of serum albumin concentrations and estimated glomerular filtration rate (eGFR; by CKD-EPI equation), respectively. PTA (target of 100%fT_>MIC) was 91% for patients with eGFR of 33 mL/min and 1 g q6h, 87% for patients with eGFR of 96 mL/min and 2 g q4h and 71% for patients with eGFR of 153 mL/min and 2 g q4h.

Conclusions

For patients with high creatinine clearance who are infected with moderately susceptible pathogens, therapeutic drug monitoring is advised since there is a risk of underexposure to flucloxacillin. Due to the non-linear protein binding of flucloxacillin and the high prevalence of hypoalbuminaemia in critically ill patients, dose adjustments should be based on unbound concentrations.

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.

Resistance Detection and Transmission Risk Analysis of Pig-Derived Pathogenic Escherichia coli in East China

Objective: Antibiotics play an essential role in the treatment and prevention of diseases in pig farms. However, the irrational use of antibiotics leads to the emergence of multi-drug resistance of bacteria, which poses a critical threat to the efficacy of antibiotic treatments. Therefore, the study is designed to analyze the drug resistance of pathogenic Escherichia coli isolated from large-scale pig farms in East China, which provides a theoretical basis for precisely targeted clinical drugs in swine farms. Method: The pathogenic E. coli were isolated and identified from clinical samples of swine farms, and the drug resistance of pathogenic E. coli was detected by antimicrobial susceptibility test (AST) and minimum inhibitory concentration test (MIC). Moreover, the prevalence of plasmid-mediated β-lactam resistance genes was analyzed by PCR. Results: A total of 67 pathogenic E. coli were isolated from 152 samples collected from 20 large-scale pig farms in East China. All isolated pathogenic E. coli are associated with severe drug resistance. Moreover, 70% of isolated pathogenic E. coli is resistant to more than four antibiotics. Besides, there were 19 serotypes including O2, O4, O5, O6, O14, O26, O38, O42, O49, O57, O92, O93, O95, O101, O121, O131, O143, O158, and O161, of which the O4 and O92 serotype were the main serotypes in swine farms. The main extended-spectrum beta-lactamases (ESBLs)-encoding genes in East China were bla _CTX-M, bla _TEM, and bla _OXA by the detection of the ESBLs encoding genes of porcine pathogenic E. coli. The conjugation assays showed that a total of 30 transconjugants were obtained by conjugation, which indicated that drug resistance genes could be transmitted horizontally through conjugative plasmids. Conclusion: The isolated pathogenic E. coli were all multi-drug resistant, and especially O4 and O92 were the main serotypes. The β-lactam resistance genes were prevalent in large-scale pig farms in East China, which provided a theoretical basis for the prevention and control of pig-derived pathogenic E. coli in the future.

Towards precision medicine: Therapeutic drug monitoring-guided dosing of vancomycin and β-lactam antibiotics to maximize effectiveness and minimize toxicity

PURPOSE

The goal of this review is to explore the role of antimicrobial therapeutic drug monitoring (TDM), especially in critically ill, obese, and older adults, with a specific focus on β-lactams and vancomycin.

SUMMARY

The continued rise of antimicrobial resistance prompts the need to optimize antimicrobial dosing. The aim of TDM is to individualize antimicrobial dosing to achieve antibiotic exposures associated with improved patient outcomes. Initially, TDM was developed to minimize adverse effects during use of narrow therapeutic index agents. Today, patient and organism complexity are expanding the need for precision dosing through TDM services. Alterations of pharmacokinetics and pharmacodynamics (PK/PD) in the critically ill, obese, and older adult populations, in conjunction with declining organism susceptibility, complicate attainment of therapeutic targets. Over the last decade, antimicrobial TDM has expanded with the emergence of literature supporting β-lactam TDM and a shift from monitoring vancomycin trough concentrations to monitoring of the ratio of area under the concentration (AUC) curve to minimum inhibitory concentration (MIC). PK/PD experts should be at the forefront of implementing precision dosing practices.

CONCLUSION

Precision dosing through TDM is expanding and is especially important in populations with altered PK/PD, including critically ill, obese, and older adults. Due to wide PK/PD variability in these populations, TDM is vital to maximize antimicrobial effectiveness and decrease adverse event rates. However, there is still a need for studies connecting TDM to patient outcomes. Providing patient-specific care through β-lactam TDM and transitioning to vancomycin AUC/MIC monitoring may be challenging, but with experts at the forefront of this initiative, PK-based optimization of antimicrobial therapy can be achieved.

A sensitive and high-throughput quantitative liquid chromatography high-resolution mass spectrometry method for therapeutic drug monitoring of 10 β-lactam antibiotics, linezolid and two β-lactamase inhibitors in human plasma

An ultra-high pressure liquid chromatography high-resolution mass spectrometric (UHPLC-HRMS) method was developed for the simultaneous and sensitive quantification of 10 β-lactam antibiotics (cefepime, meropenem, amoxicillin, cefazolin, benzylpenicillin, ceftazidime, piperacillin, flucloxacillin, cefuroxime and aztreonam), linezolid and β-lactamase inhibitors tazobactam and clavulanic acid in human plasma. Validation according to the EMA guidelines showed excellent within- and between-run accuracy and precision (i.e. between 1.1 and 8.5%) and high sensitivity (i.e. lower limit of quantification between 0.25 and 1 mg/L). The UHPLC-HRMS method enables a short turnaround time and high sensitivity and needs only a small amount of plasma, allowing appropriate routine therapeutic drug monitoring. The short turnaround time is obtained by speeding up the protocol on multiple levels, i.e. fast and workload-efficient sample preparation (i.e. protein precipitation and dilution), short (4 min) instrument run time, simultaneous measurement of all relevant β-lactam antibiotics used in the intensive care unit and the use of the same instrument, column and mobile phases as for the other routine methods in our laboratory.

A guide to therapeutic drug monitoring of β-lactam antibiotics

Therapeutic drug monitoring (TDM) opens the door to personalized medicine, yet it is infrequently applied to β-lactam antibiotics, one of the most commonly prescribed drug classes in the hospital setting. As we continue to understand more about β-lactam pharmacodynamics (PD) and wide inter- and intra-patient variability in pharmacokinetics (PK), the utility of TDM has become increasingly apparent. For β-lactams, the time that free concentrations remain above the minimum inhibitory concentration (MIC) as a function of the dosing interval (%fT>MIC) has been shown to best predict antibacterial effect. Many studies have shown that β-lactam %fT>MIC exposures are often suboptimal across a wide variety of disease states and clinical settings. A limitation to implementing this practice is the general lack of understanding on how to best operationalize this intervention and interpret the results. The instrumentation and expertise needed to quantify β-lactams for TDM is rarely available locally, but certain laboratories advertise these services and perform them regularly. Familiarity with the modalities and nuances of antimicrobial susceptibility testing is crucial to establishing β-lactam concentration targets that meet the relevant exposure thresholds. Evaluation of these concentrations is best accomplished using population PK software and Bayesian modeling, for which a multitude of programs are available. While TDM of β-lactams has shown an ability to increase the rate of target attainment, there is currently limited evidence to suggest that it leads to improved clinical outcomes. Although consensus guidelines for β-lactam TDM do not exist in the United States, guidance would help to promote this important practice and better standardize the approach across institutions. Herein, we discuss the basis for β-lactam TDM, review supporting evidence, and provide guidance for implementation in specific patient populations.

An isotope-dilution LC-MS/MS method for the simultaneous quantification of meropenem and its open-ring metabolite in serum

BACKGROUND

Therapeutic drug monitoring (TDM) of beta-lactam antibiotics and, among them, especially meropenem gains importance in the field of laboratory medicine. Meropenem is known to be unstable, resulting in a degradation product with an open beta-lactam ring. For a more comprehensive TDM of meropenem, the aim was to develop a LC-MS/MS method for the simultaneous quantification of meropenem and its main degradation product, the open-ring metabolite (ORM).

METHODS

The method involves a protein precipitation followed by chromatographic separation using a formic acid-ammonium formate methanol gradient on a pentafluorophenyl column. Multiple reaction monitoring in the positive ion mode and stable isotope labeled internal standards were used for quantification. Validation was performed according to the European Medicines Agency guideline.

RESULTS

Validation was successful performed within the linear drug concentration range of 1.0-100.0 mg/l for meropenem and 0.62-62.30 mg/l for the ORM. Investigation of selectivity, accuracy and precision showed good results and potential matrix effects were successfully compensated by the internal standards. The suitability of the method was shown by the comparison of 35 anonymized leftover serum samples from intensive care patients with routine analyses.

CONCLUSION

For the first time, we herein describe a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of meropenem and its ORM in human serum. The ratio of active to inactive compound provides valuable pharmaceutical and pharmacokinetic information, which may contribute to therapeutic efficacy.

Personalized antibiotic therapy – a rapid high performance liquid chromatography–tandem mass spectrometry method for the quantitation of eight antibiotics and voriconazole for patients in the intensive care unit

Objectives

For a long time, the therapeutic drug monitoring of anti-infectives (ATDM) was recommended only to avoid the toxic side effects of overdosing. During the last decade, however, this attitude has undergone a significant change. Insufficient antibiotic therapy may promote the occurrence of drug resistance; therefore, the “one-dose-fits-all” principle can no longer be classified as up to date. Patients in intensive care units (ICU), in particular, can benefit from individualized antibiotic therapies.

Methods

Presented here is a rapid and sufficient LC-MS/MS based assay for the analysis of eight antibiotics (ampicillin, cefepime, cefotaxime, ceftazidime, cefuroxime, linezolid, meropenem, and piperacillin) applicated by continuous infusion and voriconazole. In addition a dose adjustment procedure for individualized antibiotic therapy has been established.

Results

The suggested dose adjustments following the initial dosing of 121 patient samples from ICUs, were evaluated over a period of three months. Only a minor percentage of the serum levels were found to be within the target range while overdosing was often observed for β-lactam antibiotics, and linezolid tended to be often underused. The results demonstrate an appreciable potential for β-lactam savings while enabling optimal therapy.

Conclusions

The presented monitoring method provides high specificity and is very robust against various interferences. A fast and straightforward method, the developed routine ensures rapid turnaround time. Its application has been well received by participating ICUs and has led to an expanding number of hospital wards participating in ATDM.

Aptamer-Based Detection of Ampicillin in Urine Samples

The misuse of antibiotics in health care has led to increasing levels of drug resistant infections (DRI's) occurring in the general population. Most technologies developed for the detection of DRI's typically focus on phenotyping or genotyping bacterial resistance rather than on the underlying cause and spread of DRI's; namely the misuse of antibiotics. An aptameric based assay has been developed for the monitoring of ampicillin in urine samples, for use in determining optimal antibiotic dosage and monitoring patient compliance with treatment. The fluorescently labelled aptamers were shown to perform optimally at pH 7, ideal for buffered clinical urine samples, with limits of detection as low as 20.6 nM, allowing for determination of ampicillin in urine in the clinically relevant range of concentrations (100 nM to 100 µM). As the assay requires incubation for only 1 h with a small sample volume, 50 to 150 µL, the test would fit within current healthcare pathways, simplifying the adoption of the technology.

Failure of target attainment of beta-lactam antibiotics in critically ill patients and associated risk factors: a two-center prospective study (EXPAT)

Background

Early and appropriate antibiotic dosing is associated with improved clinical outcomes in critically ill patients, yet target attainment remains a challenge. Traditional antibiotic dosing is not suitable in critically ill patients, since these patients undergo physiological alterations that strongly affect antibiotic exposure. For beta-lactam antibiotics, the unbound plasma concentrations above at least one to four times the minimal inhibitory concentration (MIC) for 100% of the dosing interval (100%ƒT > 1–4×MIC) have been proposed as pharmacodynamic targets (PDTs) to maximize bacteriological and clinical responses. The objectives of this study are to describe the PDT attainment in critically ill patients and to identify risk factors for target non-attainment.

Methods

This prospective observational study was performed in two ICUs in the Netherlands. We enrolled adult patients treated with the following beta-lactam antibiotics: amoxicillin (with or without clavulanic acid), cefotaxime, ceftazidime, ceftriaxone, cefuroxime, and meropenem. Based on five samples within a dosing interval at day 2 of therapy, the time unbound concentrations above the epidemiological cut-off (ƒT > MIC_ECOFF and ƒT > 4×MIC_ECOFF) were determined. Secondary endpoints were estimated multivariate binomial and binary logistic regression models, for examining the association of PDT attainment with patient characteristics and clinical outcomes.

Results

A total of 147 patients were included, of whom 63.3% achieved PDT of 100%ƒT > MIC_ECOFF and 36.7% achieved 100%ƒT > 4×MIC_ECOFF. Regression analysis identified male gender, estimated glomerular filtration rate (eGFR) ≥ 90 mL/min/1.73 m², and high body mass index (BMI) as risk factors for target non-attainment. Use of continuous renal replacement therapy (CRRT) and high serum urea significantly increased the probability of target attainment. In addition, we found a significant association between the 100%ƒT > MIC_ECOFF target attainment and ICU length of stay (LOS), but no significant correlation was found for the 30-day survival.

Conclusions

Traditional beta-lactam dosing results in low target attainment in the majority of critically ill patients. Male gender, high BMI, and high eGFR were significant risk factors for target non-attainment. These predictors, together with therapeutic drug monitoring, may help ICU clinicians in optimizing beta-lactam dosing in critically ill patients.

Trial registration

Netherlands Trial Registry (EXPAT trial), NTR 5632. Registered on 7 December 2015.

Non-invasive Drug Monitoring of β-Lactam Antibiotics Using Sweat Analysis-A Pilot Study

Background: Antimicrobial resistance is a major challenge in treating infectious diseases. Therapeutic drug monitoring (TDM) can optimize and personalize antibiotic treatment. Previously, antibiotic concentrations in tissues were extrapolated from skin blister studies, but sweat analyses for TDM have not been conducted. Objective: To investigate the potential of sweat analysis as a non-invasive, rapid, and potential bedside TDM method. Methods: We analyzed sweat and blood samples from 13 in-house patients treated with intravenous cefepime, imipenem, or flucloxacillin. For cefepime treatment, full pharmacokinetic sampling was performed (five subsequent sweat samples every 2 h) using ultra-high-performance liquid chromatography coupled with triple quadrupole mass spectrometry. The ClinicalTrials.gov registration number is NCT03678142. Results: In this study, we demonstrated for the first time that flucloxacillin, imipenem, and cefepime are detectable in sweat. Antibiotic concentration changes over time demonstrated comparable (age-adjusted) dynamics in the blood and sweat of patients treated with cefepime. Patients treated with standard flucloxacillin dosage showed the highest mean antibiotic concentration in sweat. Conclusions: Our results provide a proof-of-concept that sweat analysis could potentially serve as a non-invasive, rapid, and reliable method to measure antibiotic concentration and as a surrogate marker for tissue penetration. If combined with smart biosensors, sweat analysis may potentially serve as the first lab-independent, non-invasive antibiotic TDM method.

Therapeutic drug monitoring of β-lactam antibiotics in the ICU

INTRODUCTION

Individualizing antibiotic therapy is paramount to improve clinical outcomes while minimizing the risk of toxicity and antimicrobial therapy. β-lactam antibiotics are amongst the drugs most commonly prescribed in the Intensive Care Unit (ICU). The pharmacokinetics of β-lactam antibiotics are profoundly altered in critically ill patients, leading to the failure of standard drug dosing regimens to result in adequate drug concentrations. Therapeutic Drug Monitoring (TDM) of β-lactam antibiotics is a promising tool to help optimize β-lactam antibiotic therapy.

AREAS COVERED

The rationale behind TDM for β-lactam antibiotics is explained, as well as some more practical aspects such as when to sample, what concentrations to strive for and how to use it in clinical practice. We also discuss microbiological and analytical considerations, knowledge gaps, and future perspectives of β-lactam antibiotics TDM in ICU patients.

EXPERT OPINION

TDM of β-lactam antibiotics has been studied intensively in recent years. While TDM may not yet be widely available, and targets need to be further refined, TDM of β-lactam antibiotics will help to optimize antibiotic therapy in the critically ill patient, as an integrated part of an antimicrobial stewardship program.

On-Site Therapeutic Drug Monitoring

Recent technological advances have stimulated efforts to bring personalized medicine into practice. Yet, traditional application fields like therapeutic drug monitoring (TDM) have remained rather under-appreciated. Owing to clear dose-response relationships, TDM could improve patient outcomes and reduce healthcare costs. While chromatography-based routine practices are restricted due to high costs and turnaround times, biosensors overcome these limitations by offering on-site analysis. Nevertheless, sensor-based approaches have yet to break through for clinical TDM applications, due to the gap between scientific and clinical communities. We provide a critical overview of current TDM practices, followed by a TDM guideline to establish a common ground across disciplines. Finally, we discuss how the translation of sensor systems for TDM can be facilitated, by highlighting the challenges and opportunities.

A rapid, automatic and accurate assay for quantifying temocillin in human serum and CSF using turbulent flow liquid chromatography coupled to high-resolution mass spectrometry. Clinical application

Temocillin is a β-lactamase-resistant penicillin used for the treatment of multiple drug-resistant Gram-negative bacteria. To maximize efficacy and avoid adverse effects, the dose regimen has to be quickly adjusted to the clinical situations. This necessitates the development of a rapid, reliable and accurate analytical method. Temocillin and the stable isotopically labeled internal standard ([¹³ C₆ ]-amoxicillin) were extracted from either serum or cerebrospinal fluid by a turbulent flow liquid chromatographic method and eluted onto an octadecyl-silica phase with polar endcapping. Mass spectrometry was conducted using an exact mass determination method by electrospray positive ionization high-resolution mass spectrometry. The LLOQ and ULOQ of the present method were determined to be 0.4 and 200 μg/ml for serum and cerebrospinal fluid samples, respectively. The total analysis time was <7 min. The recovery ranged from 87.7 to 120.8%. Intra- and inter-day precision and trueness were tested at four concentration levels: 0.4, 8, 40 and 160 μg/ml. Values were 6.33 ± 1.53, 8.8 ± 1.3, 8.8 ± 0.36 and 2.1 ± 0.76%, and 5.0 ± 0.54, 9.9 ± 1.0, 5.8 ± 1.6 and 0.1 ± 1.1%, for inter- and intra-day analysis, respectively. Temocillin was found to be stable under all relevant laboratory conditions. The method was cross-validated with a microbiological assay. This method is suitable for accurate measurement of temocillin concentration in small volumes of serum or cerebrospinal fluid. Thanks to the online extraction procedure, the overall analytical time is compatible with high-throughput analysis for clinical application.

Antibiotic prophylaxis with high-dose cefoxitin in bariatric surgery: an observational prospective single center study

BACKGROUND

The optimal dose of cefoxitin for antibiotic prophylaxis in obese patients remains uncertain. We evaluated the adequacy of a 4-gram dosing regimen of cefoxitin against the most frequent pathogens that infect patients undergoing bariatric surgery.

METHODS

This observational prospective study included obese patients who required bariatric surgery and a 4-gram dose of cefoxitin as an antibiotic prophylaxis. Serum concentrations were measured during surgery (incision, wound closure and in case of reinjection). The pharmacokinetic/pharmacodynamic (PK/PD) target was to obtain free cefoxitin concentrations above 4× MIC, from incision to wound closure (100% ƒT_>4xMIC). The targeted MIC was based on the worst-case scenario (the highest ECOFF value of Staphylococcus aureus, Enterobacteriaceae and anaerobic bacteria). The secondary outcomes were the factors related to underdosage.

RESULTS

Two hundred patients were included. The mean age of the patients was 46 (±12) years-old, and the mean BMI was 45.8 (±6.9) kg/m² Bypass surgery was the preferred technique (84%). The percentages of patients who met the PK/PD target (100% fT_>4xMIC) of cefoxitin were 37.3%, 1.1% and 0% for S. aureus, Enterobacteriaceae and anaerobic bacteria, respectively. BMIs below 50 kg/m² (OR 0.29, 95% CI [0.11-0.75], P = 0.0107) and a shorter duration of surgery (OR 0.97, 95% CI [0.95-0.99], P = 0.004) were associated with reaching the target concentrations.

CONCLUSIONS

In obese patients undergoing bariatric surgery, a regimen of 4 grams of cefoxitin led to an inadequate coverage for most common pathogens. A longer surgery duration and BMI over 50 kg/m² increase the risk of underdosage.

Pharmacokinetic variability of beta-lactams in critically ill patients: A narrative review

The use of antibacterial drugs is very common in critically ill patients and beta-lactam agents are widely used in this context. Critically ill patients show several characteristics (e.g., sepsis, renal impairment or conversely augmented renal clearance, renal replacement therapy) that may alter beta-lactam pharmacokinetics (PK) in comparison with non-critically ill patients. This narrative literature review aims to identify recent studies quantifying the variability of beta-lactams volume of distribution and clearance and to determine its main determinants. Seventy studies published between 2000 and 2018 were retained. Data on volume of distribution and clearance variability were reported for 5 penicillins, 3 beta-lactamase inhibitors, 6 cephalosporins and 4 carbapenems. Data confirm specific changes in PK parameters and important variability of beta-lactam PK in critically ill patients. Renal function, body weight and use of renal replacement therapy are the principal factors influencing PK parameters described in this population. Few studies have directly compared beta-lactam PK in critically ill versus non-critically ill patients. Conclusions are also limited by small study size and sparse PK data in several studies. These results suggest approaches to assess this PK variability in clinical practice. Beta-lactam therapeutic drug monitoring seems to be the best way to deal with this issue.