Maximally effective dosing regimens of meropenem in patients with septic shock

Relationship between Target Time above Minimum Inhibitory Concentration Achievement Rate of Meropenem Using Monte Carlo Simulation and In-Hospital Survival in Patients with Pseudomonas aeruginosa Bacteremia

Pseudomonas aeruginosa bacteremia is associated with a high mortality rate, and meropenem (MEPM) is commonly used to treat it. However, the relationship between the time above the minimum inhibitory concentration (fT>MIC) of MEPM and its therapeutic efficacy in P. aeruginosa bacteremia has not been explored. This study aimed to investigate this relationship by defining the target % fT>MIC of MEPM as 75%. The retrospective study spanned 14 years and included hospitalized patients treated with MEPM for P. aeruginosa bacteremia. Monte Carlo simulation was used to calculate the probability of target attainment (PTA) for each patient, and the threshold for a PTA of 75% fT>MIC associated with in-hospital survival was determined using receiver operating characteristic (ROC) curves. The ROC curve-derived PTA associated with improved in-hospital survival was 65.0%, a significant finding in multivariate logistic regression analysis adjusted for patient background factors (odds ratio: 20.49, 95% confidence interval: 3.02-245.23, p = 0.005). This result suggests a dosing regimen that achieves a PTA of at least 65% when the target fT>MIC of MEPM for treating P. aeruginosa bacteremia is defined as 75%.

Population pharmacokinetics of antibacterial agents in the older population: a literature review

INTRODUCTION

Older individuals face an elevated risk of developing bacterial infections. The optimal use of antibacterial agents in this population is challenging because of age-related physiological alterations, changes in pharmacokinetics (PK) and pharmacodynamics (PD), and the presence of multiple underlying diseases. Therefore, population pharmacokinetics (PPK) studies are of great importance for optimizing individual treatments and prompt identification of potential risk factors.

AREA COVERED

Our search involved keywords such as 'elderly,' 'old people,' and 'geriatric,' combined with 'population pharmacokinetics' and 'antibacterial agents.' This comprehensive search yielded 11 categories encompassing 28 antibacterial drugs, including vancomycin, ceftriaxone, meropenem, and linezolid. Out of 127 studies identified, 26 (20.5%) were associated with vancomycin, 14 (11%) with meropenem, and 14 (11%) with piperacillin. Other antibacterial agents were administered less frequently.

EXPERT OPINION

PPK studies are invaluable for elucidating the characteristics and relevant factors affecting the PK of antibacterial agents in the older population. Further research is warranted to develop and validate PPK models for antibacterial agents in this vulnerable population.

Anti-Pseudomonas aeruginosa Vaccines and Therapies: An Assessment of Clinical Trials

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes high morbidity and mortality in cystic fibrosis (CF) and immunocompromised patients, including patients with ventilator-associated pneumonia (VAP), severely burned patients, and patients with surgical wounds. Due to the intrinsic and extrinsic antibiotic resistance mechanisms, the ability to produce several cell-associated and extracellular virulence factors, and the capacity to adapt to several environmental conditions, eradicating P. aeruginosa within infected patients is difficult. Pseudomonas aeruginosa is one of the six multi-drug-resistant pathogens (ESKAPE) considered by the World Health Organization (WHO) as an entire group for which the development of novel antibiotics is urgently needed. In the United States (US) and within the last several years, P. aeruginosa caused 27% of deaths and approximately USD 767 million annually in health-care costs. Several P. aeruginosa therapies, including new antimicrobial agents, derivatives of existing antibiotics, novel antimicrobial agents such as bacteriophages and their chelators, potential vaccines targeting specific virulence factors, and immunotherapies have been developed. Within the last 2-3 decades, the efficacy of these different treatments was tested in clinical and preclinical trials. Despite these trials, no P. aeruginosa treatment is currently approved or available. In this review, we examined several of these clinicals, specifically those designed to combat P. aeruginosa infections in CF patients, patients with P. aeruginosa VAP, and P. aeruginosa-infected burn patients.

Evaluation of Empirical Dosing Regimens for Meropenem in Intensive Care Unit Patients Using Population Pharmacokinetic Modeling and Target Attainment Analysis

In the present study, population pharmacokinetic (PK) analysis was performed based on meropenem data from a prospective study conducted in 114 critically ill patients with a wide range of renal functions and various disease conditions. The final model was a one-compartment model with linear elimination, with creatinine clearance and continuous renal replacement therapy affecting clearance, and total bodyweight impacting the volume of distribution. Our model is a valuable addition to the existing meropenem population PK models, and it could be particularly useful during implementation of a therapeutic drug monitoring program combined with Bayesian forecasting. Based on the final model developed, comprehensive Monte Carlo simulations were performed to evaluate the probability of target attainment (PTA) of 16 different dosing regimens. Simulation results showed that 2 g administered every 8 h with 3-h prolonged infusion (PI) and 4 g/day by continuous infusion (CI) appear to be two empirical dosing regimens that are superior to many other regimens when both target attainment and potential toxicity are considered and renal function information is not available. Following a daily CI dose of 6 g or higher, more than 30% of the population with a creatinine clearance of <60 mL/min is predicted to have neurotoxicity. With the availability of institution- and/or unit-specific meropenem susceptibility patterns, as well as an individual patient's renal function, our PTA results may represent useful references for physicians to make dosing decisions.

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.

Optimizing Clinical Outcomes Through Rational Dosing Strategies: Roles of Pharmacokinetic/Pharmacodynamic Modeling Tools

Significant progress in previous decades has led to several methodologies developed to facilitate the design of optimal antimicrobial dosing. In this review, we highlight common pharmacokinetic/pharmacodynamic (PKPD) modeling techniques and their roles in guiding rational dosing regimen design. In the early drug development phases, dose fractionation studies identify the PKPD index most closely associated with bacterial killing. Once discerned, this index is linked to clinical efficacy end points, and classification and regression tree analysis can be used to define the PKPD target goal. Monte Carlo simulations integrate PKPD and microbiological data to identify dosing strategies with a high probability of achieving the established PKPD target. Results then determine dosing regimens to investigate and/or validate the findings of randomized controlled trials. Further improvements in PKPD modeling could lead to an era of precision dosing and personalized therapeutics.

Optimizing Meropenem in Highly Resistant Klebsiella pneumoniae Environments: Population Pharmacokinetics and Dosing Simulations in Critically Ill Patients

Critically ill patients are characterized by substantial pathophysiological changes that alter the pharmacokinetics (PK) of hydrophilic antibiotics, including carbapenems. Meropenem is a key antibiotic for multidrug-resistant Gram-negative bacilli, and such pathophysiological alterations can worsen treatment outcomes. This study aimed to determine the population PK of meropenem and to propose optimized dosing regimens for the treatment of multidrug-resistant Klebsiella pneumoniae in critically ill patients. Two plasma samples were collected from eligible patients over a dosing interval. Nonparametric population PK modeling was performed using Pmetrics. Monte Carlo simulations were applied to different dosing regimens to determine the probability of target attainment and the cumulative fraction of response, taking into account the local MIC distribution for K. pneumoniae. The targets of 40% and 100% for the fraction of time that free drug concentrations remained above the MIC (ƒT>MIC) were tested, as suggested for critically ill patients. A one-compartment PK model using data from 27 patients showed high interindividual variability. Significant PK covariates were the 8-h creatinine clearance for meropenem and the presence of an indwelling catheter for pleural, abdominal, or cerebrospinal fluid drainage for the meropenem volume of distribution. The target 100% ƒT>MIC for K. pneumoniae, with a MIC of ≤2 mg/liter, could be attained by the use of a continuous infusion of 2.0 g/day. Meropenem therapy in critically ill patients could be optimized for K. pneumoniae isolates with an MIC of ≤2 mg/liter by using a continuous infusion in settings with more than 50% isolates have a MIC of ≥32mg/L.

Why We May Need Higher Doses of Beta-Lactam Antibiotics: Introducing the 'Maximum Tolerable Dose'

The surge in antimicrobial resistance and the limited availability of new antimicrobial drugs has fueled the interest in optimizing antibiotic dosing. An ideal dosing regimen leads to maximal bacterial cell kill, whilst minimizing the risk of toxicity or antimicrobial resistance. For beta-lactam antibiotics specifically, PK/PD-based considerations have led to the widespread adoption of prolonged infusion. The rationale behind prolonged infusion is increasing the percentage of time the beta-lactam antibiotic concentration remains above the minimal inhibitory concentration (%fT>MIC). The ultimate goal of prolonged infusion of beta-lactam antibiotics is to improve the outcome of infectious diseases. However, merely increasing target attainment (or the %fT>MIC) is unlikely to lead to improved clinical outcome for several reasons. First, the PK/PD index and target are dynamic entities. Changing the PK (as is the case if prolonged instead of intermittent infusion is used) will result in different PK/PD targets and even PK/PD indices necessary to obtain the same level of bacterial cell kill. Second, the minimal inhibitory concentration is not a good denominator to describe either the emergence of resistance or toxicity. Therefore, we believe a different approach to antibiotic dosing is necessary. In this perspective, we introduce the concept of the maximum tolerable dose (MTD). This MTD is the highest dose of an antimicrobial drug deemed safe for the patient. The goal of the MTD is to maximize bacterial cell kill and minimize the risk of antimicrobial resistance and toxicity. Unfortunately, data about what beta-lactam antibiotic levels are associated with toxicity and how beta-lactam antibiotic toxicity should be measured are limited. This perspective is, therefore, a plea to invest in research aimed at deciphering the dose−response relationship between beta-lactam antibiotic drug concentrations and toxicity. In this regard, we provide a theoretical approach of how increasing uremic toxin concentrations could be used as a quantifiable marker of beta-lactam antibiotic toxicity.

External Evaluation of Population Pharmacokinetic Models to Inform Precision Dosing of Meropenem in Critically Ill Patients

Routine clinical meropenem therapeutic drug monitoring data can be applied to model-informed precision dosing. The current study aimed to evaluate the adequacy and predictive capabilities of the published models with routine meropenem data and identify the dosing adaptations using a priori and Bayesian estimation. For this, 14 meropenem models for the external evaluation carried out on an independent cohort of 134 patients with 205 meropenem concentrations were encoded in NONMEM 7.3. The performance was determined using: 1) prediction-based and simulation-based diagnostics; and 2) predicted meropenem concentrations by a priori prediction using patient covariates only; and Bayesian forecasting using previous observations. The clinical implications were assessed according to the required dose adaptations using the meropenem concentrations. All assessments were stratified based on the patients with or without continuous renal replacement therapy. Although none of the models passed all tests, the model by Muro et al. showed the least bias. Bayesian forecasting could improve the predictability over an a priori approach, with a relative bias of −11.63–68.89% and −302.96%–130.37%, and a relative root mean squared error of 34.99–110.11% and 14.78–241.81%, respectively. A dosing change was required in 40.00–68.97% of the meropenem observation results after Bayesian forecasting. In summary, the published models couldn’t adequately describe the meropenem pharmacokinetics of our center. Although the selection of an initial meropenem dose with a priori prediction is challenging, the further model-based analysis combining therapeutic drug monitoring could be utilized in the clinical practice of meropenem therapy.

Use of the Hollow-Fiber Infection Model to Measure the Effect of Combination Therapy of Septic Shock Exposures of Meropenem and Ciprofloxacin against Intermediate and Resistant Pseudomonas aeruginosa Clinical Isolates

Meropenem-ciprofloxacin combination therapy was compared to the respective monotherapy in a Hollow-Fiber Infection Model against two Pseudomonas aeruginosa isolates. Following initial kill of ∼ 5-logs by each monotherapy, rapid regrowth occurred within 24 h, reaching 10⁸ - 10¹⁰ CFU/mL at 120 h. In contrast, combination therapy achieved > 5-log kill within 6 h and suppressed bacterial regrowth throughout. The results suggest that meropenem-ciprofloxacin combination may provide significantly enhanced bacterial killing and resistance suppression against P. aeruginosa.

Meropenem Target Attainment and Population Pharmacokinetics in Critically Ill Septic Patients with Preserved or Increased Renal Function

Purpose

Critically ill patients with preserved or increased renal function have been shown to be at risk of underexposure to meropenem. Although many meropenem population pharmacokinetic (PK) models have been published, there is no large prospective population PK study with rich sampling focusing on patients most at risk of suboptimal pharmacokinetic/pharmacodynamic (PK/PD) target attainment. Therefore, the aim of the present study was to evaluate PK/PD target attainment and to perform a thorough covariate screening using population PK modelling of meropenem in septic patients with preserved or increased renal function.

Patients and Methods

A single-centre prospective observational PK study was performed in the intensive care unit (ICU) of the University Hospitals Leuven. Patients with severe sepsis or septic shock and treated with meropenem in the ICU were screened for inclusion. Patients were excluded if they received renal replacement therapy or had an estimated glomerular filtration rate according to the Chronic Kidney Disease Epidemiology collaboration equation <70 mL/min/1.73m² on the day of PK sampling. Successful PK/PD target attainment was defined as an unbound meropenem trough concentration above 2 mg/L or 8 mg/L. Population PK modelling was performed with NONMEM7.4.

Results

In total, 58 patients were included, contributing 345 plasma samples over 70 dosing intervals. The 2 mg/L and 8 mg/L targets were successfully attained in 46% and 11% of all dosing intervals, respectively. A two-compartment population PK model with linear elimination and interindividual variability on clearance best described meropenem PK. The estimated creatinine clearance according to the Cockcroft-Gault equation was the only covariate retained during population PK analysis.

Conclusion

This study provided detailed insight into meropenem PK in critically ill patients with preserved or increased renal function. We observed poor PK/PD target attainment, for which renal function was the only significant covariate.

Trial Registration

This study is registered at ClinicalTrials.gov (NCT03560557).

Pharmacokinetics of meropenem in critically ill patients in Saudi Arabia

Background

Meropenem is commonly used in the ICU to treat gram-negative infections. Due to various pathophysiological changes, critically ill patients are at higher risk of having subtherapeutic concentrations and hence have a higher risk of treatment failure—especially in regions where gram-negative drug resistance is increasing, such as Saudi Arabia. No studies have evaluated the pharmacokinetics of meropenem in critically ill patients in Saudi Arabia. Our primary objective is to assess the percentage of patients achieving the therapeutic target for meropenem.

Methods

This prospective observational study was conducted in the ICUs of King Khalid University Hospital. Patient were included if >18 years-of-age and received meropenem for a clinically suspected or proven bacterial infection. The primary outcome was to assess the percentage of patients who achieved the pharmacokinetic/pharmacodynamic (PKPD) therapeutic target of a free trough concentration four times the MIC. The secondary outcome was to estimate the pharmacokinetics of meropenem. Pharmacokinetic analysis was performed using Monolix Suite 2020R1 (Lixoft, France).

Results

Trough concentrations were highly variable and ranged from <0.5 µg/mL to 39 µg/mL, with a mean ± SD trough concentration of 8.5 ± 8 µg/mL. Only 46% of patients achieved the therapeutic target. The only significant predictor of failing to achieve the PKPD target was augmented renal clearance.

Conclusion

In conclusion, more than half of our patients did not achieve the PKPD target. Thus, there is a need for better dosing strategies of meropenem in critically ill patients in Saudi Arabia such as extended and continuous infusion.

Does Prolonged Infusion Time Really Improve the Efficacy of Meropenem Therapy? A Prospective Study in Critically Ill Patients

Introduction

Meropenem is a carbapenem antibiotic, which has demonstrated excellent antimicrobial activity against gram-negative clinical isolates. It is also commonly used in critically ill patients. This study aimed to determine the pharmacokinetics/pharmacodynamics of meropenem in critically ill patients and whether prolonged injection duration is really beneficial to meropenem therapy.

Methods

We included 209 samples in 64 patients in this prospective study. PPK analysis and Monte Carlo dosing simulations were developed using Phoenix.

Results

A two-compartment model described the data adequately. Clearance (CL), volume (V), clearance of peripheral compartment (CL₂), and volume of peripheral compartment (V₂) were 6.15 l/h, 2.83 l/h, 17.40 l, and 17.48 l, respectively. Creatinine clearance and uric acid were significant covariates. Patients with creatinine clearance ≤ 60 ml/min and uric acid > 400 μmol/l could achieve the target > 90% under the minimum inhibitory concentration (MIC) of 8 mg/l, even with the administration dose of 500 mg/8 h with a 2-h infusion. Prolonging the infusion time significantly improved the therapeutic effect when MIC < 4. However, for the pharmacodynamic (PD) effects of 100% fT > MIC and 100% fT > 4 MIC, no significant statistical difference was observed in critically ill patients.

Conclusions

Critically ill patients with lower creatinine clearance and higher uric acid levels tended to need a lower dosage of meropenem. Prolonged infusion time was not always beneficial for those who needed a higher therapeutic target (100% fT > MIC, 100% fT > 4 MIC) or with MIC > 4 mg/l. Increasing dose or alternative therapeutic strategies may be required for critically ill patients with drug-resistant or severe infections. The study is of great significance to guide the rational use of meropenem in critically ill patients.

Trial Registration

The trial was registered in the China Clinical Trial (ChiCTR1900020672). Registered on 12 January 2019.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00551-2.

Meropenem is commonly used empirically or targeted in critically ill patients for bacterial infection. Many studies have reported that prolonged infusion time can improve the efficacy of meropenem therapy. However, we are skeptical about that. Meanwhile, prolonged injections can sometimes cause mobility problems for patients. A quantitative method is used to evaluate meropenem use. It is called the population pharmacokinetic model or pharmacodynamic study. Using this method, we found two significant influencing factors of meropenem metabolism: creatinine clearance and uric acid level. It is likely that patients with a lower level of creatinine clearance and a high uric acid level tend to require lower dosages of meropenem. As for the effect of infusion time, Monte Carlo simulation was used, which can do 3000 simulations on an individual. The result was complex. We found infusion time was beneficial only when bacteria were sensitive to meropenem. The evidence suggests that prolonged injection duration sometimes does not significantly improve the outcome of antimicrobial therapy.

Population Pharmacokinetics of Meropenem in Critically Ill Korean Patients and Effects of Extracorporeal Membrane Oxygenation

Limited studies have investigated population pharmacokinetic (PK) models and optimal dosage regimens of meropenem for critically ill adult patients using the probability of target attainment, including patients receiving extracorporeal membrane oxygenation (ECMO). A population PK analysis was conducted using non-linear mixed-effect modeling. Monte Carlo simulation was used to determine for how long the free drug concentration was above the minimum inhibitory concentration (MIC) at steady state conditions in patients with various degrees of renal function. Meropenem PK in critically ill patients was described using a two-compartment model, in which glomerular filtration rate was identified as a covariate for clearance. ECMO did not affect meropenem PK. The simulation results showed that the current meropenem dosing regimen would be sufficient for attaining 40%fT_>MIC for Pseudomonas aeruginosa at MIC ≤ 4 mg/L. Prolonged infusion over 3 h or a high-dosage regimen of 2 g/8 h was needed for MIC > 2 mg/L or in patients with augmented renal clearance, for a target of 100%fT_>MIC or 100%fT_>4XMIC. Our study suggests that clinicians should consider prolonged infusion or a high-dosage regimen of meropenem, particularly when treating critically ill patients with augmented renal clearance or those infected with pathogens with decreased in vitro susceptibility, regardless of ECMO support.

Ceftolozane/tazobactam versus meropenem in patients with ventilated hospital-acquired bacterial pneumonia: subset analysis of the ASPECT-NP randomized, controlled phase 3 trial

Background

Ceftolozane/tazobactam is approved for treatment of hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP) at double the dose approved for other infection sites. Among nosocomial pneumonia subtypes, ventilated HABP (vHABP) is associated with the lowest survival. In the ASPECT-NP randomized, controlled trial, participants with vHABP treated with ceftolozane/tazobactam had lower 28-day all-cause mortality (ACM) than those receiving meropenem. We conducted a series of post hoc analyses to explore the clinical significance of this finding.

Methods

ASPECT-NP was a multinational, phase 3, noninferiority trial comparing ceftolozane/tazobactam with meropenem for treating vHABP and VABP; study design, efficacy, and safety results have been reported previously. The primary endpoint was 28-day ACM. The key secondary endpoint was clinical response at test-of-cure. Participants with vHABP were a prospectively defined subgroup, but subgroup analyses were not powered for noninferiority testing. We compared baseline and treatment factors, efficacy, and safety between ceftolozane/tazobactam and meropenem in participants with vHABP. We also conducted a retrospective multivariable logistic regression analysis in this subgroup to determine the impact of treatment arm on mortality when adjusted for significant prognostic factors.

Results

Overall, 99 participants in the ceftolozane/tazobactam and 108 in the meropenem arm had vHABP. 28-day ACM was 24.2% and 37.0%, respectively, in the intention-to-treat population (95% confidence interval [CI] for difference: 0.2, 24.8) and 18.2% and 36.6%, respectively, in the microbiologic intention-to-treat population (95% CI 2.5, 32.5). Clinical cure rates in the intention-to-treat population were 50.5% and 44.4%, respectively (95% CI − 7.4, 19.3). Baseline clinical, baseline microbiologic, and treatment factors were comparable between treatment arms. Multivariable regression identified concomitant vasopressor use and baseline bacteremia as significantly impacting ACM in ASPECT-NP; adjusting for these two factors, the odds of dying by day 28 were 2.3-fold greater when participants received meropenem instead of ceftolozane/tazobactam.

Conclusions

There were no underlying differences between treatment arms expected to have biased the observed survival advantage with ceftolozane/tazobactam in the vHABP subgroup. After adjusting for clinically relevant factors found to impact ACM significantly in this trial, the mortality risk in participants with vHABP was over twice as high when treated with meropenem compared with ceftolozane/tazobactam.

Trial registration

clinicaltrials.gov, NCT02070757. Registered 25 February, 2014, clinicaltrials.gov/ct2/show/NCT02070757.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03694-3.

Carbapenem use in critically ill patients

PURPOSE OF REVIEW

To review available data on carbapenem use in ICU. Carbapenem is a broad spectrum well tolerated antibiotic family that keep an excellent activity to extended spectrum β-lactamases and AmpC hyperproducer and in susceptible Pseudomonas aeruginosa and Acinetobacter baumannii. It becomes a drug of choice for empirical therapy of suspected sepsis in known or presumably known ESBLE carriers.

RECENT FINDINGS

Carbapenems remained the drug of choice for severe ESBLE infections. In severe critically ill patients, high off-label dose is necessary especially in patients with sepsis and glomerular hyperfiltration. Nevertheless, large spectrum of carbapenems leads to initial overuse. The increase in the overall consumption in the past years with lack of systematic re-evaluation observed is responsible of and carbapenem-selection pressure that contribute to the increase of carbapenem-resistant enterobacteriaceae, A. Baumannii and P. Aeruginosa in ICUs.

SUMMARY

Carbapenems remained a cornerstone of antibiotic therapy of severe infections. Emerging carbapenem resistance is related to the increase of carbapenem consumption. High doses are recommended for early therapy followed by systematic reevaluation on a daily basis with shift to narrow spectrum antimicrobials if possible and early stopping rules.

Key Challenges in Providing Effective Antibiotic Therapy for Critically Ill Patients with Bacterial Sepsis and Septic Shock

Early initiation of effective antibiotic therapy is vitally important for saving the lives of critically ill patients with sepsis or septic shock. The susceptibility of the infecting pathogen and the ability of the selected dosage regimen to safely achieve the required antibiotic exposure need to be carefully considered to achieve a high probability of a successful outcome. Critically ill patients commonly experience substantial pathophysiological changes that impact the functions of various organs, including the kidneys. Many antibiotics are predominantly renally eliminated and thus renal function is a major determinant of the regimen needed to achieve the required antibiotic exposure. However, currently, there is a paucity of guidelines to inform antibiotic dosing in critically ill patients, including those with sepsis or septic shock. This paper briefly reviews methods that are commonly used in critically ill patients to provide a measure of renal function, and approaches that describe the relationship between the exposure to an antibiotic and its antibacterial effects. Two common conditions that very substantially complicate the use of antibiotics in critically ill patients with sepsis, unstable renal function, and augmented renal clearance, are considered in detail and their potential therapeutic implications are explored. Suggestions are provided on how treatment of bacterial infections in critically ill patients with sepsis might be improved. Of high potential are model-informed approaches that aim to individualize initial treatment regimens based on patient and bacterial characteristics, with refinement of regimens during treatment in response to monitoring antibiotic concentrations, responsive measures of renal function, and other important clinical data.

Comparison of two empirical prolonged infusion dosing regimens for meropenem in patients with septic shock: A two-center pilot study

BACKGROUND

Due to high pharmacokinetic variability, standard doses of meropenem are frequently inadequate in septic patients. Therapeutic drug monitoring of meropenem is not widely available; therefore, improved empiric dosing recommendations are needed.

OBJECTIVES

This study aimed to compare the attainment of pharmacologic targets for two common empirical dosing regimens for meropenem in patients with septic shock.

METHODS

Two empiric dosing schemes for meropenem were compared using extended infusions (120 minutes) in 32 patients with septic shock in the intensive care units at two different hospitals. One regimen was 3 × 2 g meropenem/24 h for two days, followed by 3 × 1 g meropenem/24 h; the other regimen was 4 × 1 g meropenem/24 h. Serum meropenem concentrations were measured for the first 72 h of therapy, and pharmacokinetic modelling was performed to define the percentage of time the free drug concentration was above various target MICs for each regimen (%fT_>MIC).

RESULTS

Both regimens led to a sufficiently high %fT_>MIC for pathogens with target MICs < 4 mg/L. When higher MICs were targeted, the %fT_>MIC of 4 × 1 g meropenem decreased faster than that of 3 × 2 g meropenem. At high MICs of 32 mg/L, both dosing regimens failed to provide appropriate drug concentrations. Renal function was a significant covariate of target attainment.

CONCLUSIONS

The results of this study can guide clinicians in their choice of an empirical dosing regimen for meropenem. If pathogens with low MICs (< 4 mg/L) are targeted, both dosing regimens are adequate, whereas more resistant strains require higher doses.

Defining optimal dosing of ciprofloxacin in patients with septic shock

BACKGROUND

Patients with septic shock may undergo extensive physiological alterations that can alter antibiotic pharmacokinetics.

OBJECTIVES

To describe the population pharmacokinetics of ciprofloxacin in septic shock and to define recommendations for effective ciprofloxacin dosing in these patients.

METHODS

Adult patients with septic shock treated with ciprofloxacin were eligible for inclusion. Concentrations were measured by HPLC-MS/MS. Population pharmacokinetic modelling was performed with Monte Carlo simulations then used to define dosing regimens that optimize the PTA of an AUC/MIC ratio >125 for different MICs and fractional target attainment (FTA) of empirical and targeted therapy against Pseudomonas aeruginosa.

RESULTS

We included 48 patients with median Simplified Acute Physiology Score (SAPS) II of 49 and 90 day mortality of 33%. Ciprofloxacin pharmacokinetics was best described by a two-compartment linear model including CLCR and body weight as covariates on CL and central volume respectively. With a dose of 400 mg q8h and CLCR of 80 mL/min, >95% PTA was achieved for bacteria with MICs ≤0.25 mg/L. For empirical treatment of P. aeruginosa, 600 mg q8h only reached a maximum of 68% FTA. For directed therapy against P. aeruginosa, a dose of 600 mg q8h was needed to achieve sufficient AUC/MIC ratios.

CONCLUSIONS

In patients with septic shock, standard ciprofloxacin dosing achieved concentrations to successfully treat bacteria with MICs ≤0.25 mg/L and then only in patients with normal or reduced CLCR. To cover pathogens with higher MICs or in patients with augmented renal CL, doses may have to be increased.

External evaluation of population pharmacokinetic models for continuous administration of meropenem in critically ill adult patients

PURPOSE

Beta-lactams (BL), the most commonly prescribed class of antibiotics, are recommended as the first-line therapy for multiple indications in infectious disease guidelines. Meropenem (MERO) is frequently used in intensive care units (ICU) to treat bacterial infections with or without sepsis. The pharmacokinetics of MERO display a large variability in patients admitted to ICUs due to altered pathophysiology. The aim of this study was to perform an external evaluation of published population pharmacokinetic models of MERO in order to test their predictive performance in a cohort of ICU adult patients.

METHODS

A literature search in PubMed/Medline database was made following the PRISMA statement. External evaluation was performed using NONMEM software, and the bias and inaccuracy values were calculated.

RESULTS

An external validation dataset from the Timone Hospital in Marseille, France, included 84 concentration samples from 27 patients. Four models of MERO were identified according to the inclusion criteria of the study. None of the models presented acceptable values of bias and inaccuracy.

CONCLUSION

While performing external evaluations on some populations may confirm a model's suitability to diverse groups of patients, there is still some variability that cannot be explained nor solved by the procedure. This brings to light the difficulty to develop only one model for ICU patients and the need to develop one specific model to each population of critically ill patients.

Population pharmacokinetics and evaluation of the predictive performance of pharmacokinetic models in critically ill patients receiving continuous infusion meropenem: a comparison of eight pharmacokinetic models

Background

Several population pharmacokinetic (PopPK) models for meropenem dosing in ICU patients are available. It is not known to what extent these models can predict meropenem concentrations in an independent validation dataset when meropenem is infused continuously.

Patients and methods

A PopPK model was developed with concentration-time data collected from routine care of 21 ICU patients (38 samples) receiving continuous infusion meropenem. The predictability of this model and seven other published PopPK models was studied using an independent dataset that consisted of 47 ICU patients (161 samples) receiving continuous infusion meropenem. A statistical comparison of imprecision (mean square prediction error) and bias (mean prediction error) was conducted.

Results

A one-compartment model with linear elimination and creatinine clearance as a covariate of clearance best described our data. The mean ± SD parameter estimate for CL was 9.89 ± 3.71 L/h. The estimated volume of distribution was 48.1 L. The different PopPK models showed a bias in predicting serum concentrations from the validation dataset that ranged from -8.76 to 7.06 mg/L. Imprecision ranged from 9.90 to 42.1 mg/L.

Conclusions

Published PopPK models for meropenem vary considerably in their predictive performance when validated in an external dataset of ICU patients receiving continuous infusion meropenem. It is necessary to validate PopPK models in a target population before implementing them in a therapeutic drug monitoring program aimed at optimizing meropenem dosing.

Clinical outcomes of empirical high-dose meropenem in critically ill patients with sepsis and septic shock: a randomized controlled trial

Background

Appropriate antimicrobial dosing is challenging because of changes in pharmacokinetics (PK) parameters and an increase in multidrug-resistant (MDR) organisms in critically ill patients. This study aimed to evaluate the effects of an empirical therapy of high-dose versus standard-dose meropenem in sepsis and septic shock patients.

Methods

We performed a prospective randomized open-label study to compare the changes of modified sequential organ failure assessment (mSOFA) score and other clinical outcomes of the high-dose meropenem (2-g infusion over 3 h every 8 h) versus the standard-dose meropenem (1-g infusion over 3 h every 8 h) in sepsis and septic shock patients. Patients' characteristics, clinical and microbiological outcomes, 14 and 28-day mortality, vasopressor- and ventilator-free days, intensive care unit (ICU) and hospital-free days, percent of the time of antibiotic concentrations above the minimum inhibitory concentration (%T>MIC), and safety were assessed.

Results

Seventy-eight patients were enrolled. Median delta mSOFA was comparable between two groups (- 1 in the high-dose group vs. - 1 in the standard-dose group; P value = 0.75). There was no difference between the two groups regarding clinical and microbiological cure, 14- and 28-day mortality, vasopressor- and ventilator-free days, and ICU- and hospital-free days. In patients admitted from the emergency department (ED) with a mSOFA score ≥ 7, the high-dose group demonstrated significantly better microbiological cure compared with the standard-dose group (75% (9/12 patients) vs. 20% (2/10 patients); P value = 0.03). Likewise, the high-dose group presented higher microbiological cure rate in patients admitted from ED who had either APACHE II score > 20 (83.3% (10/12) vs. 28.6% (2/7); P value = 0.045) or on mechanical ventilator (87.5% (7/8) vs. 23.1% (3/13); P value = 0.008) than the standard-dose group. Adverse events were comparable between the two groups.

Conclusions

Empirical therapy with the high-dose meropenem presented comparable clinical outcomes to the standard-dose meropenem in sepsis and septic shock patients. Besides, subgroup analysis manifested superior microbiological cure rate in sepsis or septic shock patients admitted from ED.

Trial registration

ClinicalTrials.gov, NCT03344627, registered on November 17, 2017.

Clinical pharmacokinetics of 3-h extended infusion of meropenem in adult patients with severe sepsis and septic shock: implications for empirical therapy against Gram-negative bacteria

Background

Optimal anti-bacterial activity of meropenem requires maintenance of its plasma concentration (Cp) above the minimum inhibitory concentration (MIC) of the pathogen for at least 40% of the dosing interval (fT > MIC > 40). We aimed to determine whether a 3-h extended infusion (EI) of meropenem achieves fT > MIC > 40 on the first and third days of therapy in patients with severe sepsis or septic shock. We also simulated the performance of the EI with respect to other pharmacokinetic (PK) targets such as fT > 4 × MIC > 40, fT > MIC = 100, and fT > 4 × MIC = 100.

Methods

Arterial blood samples of 25 adults with severe sepsis or septic shock receiving meropenem 1000 mg as a 3-h EI eight hourly (Q8H) were obtained at various intervals during and after the first and seventh doses. Plasma meropenem concentrations were determined using a reverse-phase high-performance liquid chromatography assay, followed by modeling and simulation of PK data. European Committee on Antimicrobial Susceptibility Testing (EUCAST) definitions of MIC breakpoints for sensitive and resistant Gram-negative bacteria were used.

Results

A 3-h EI of meropenem 1000 mg Q8H achieved fT > 2 µg/mL > 40 on the first and third days, providing activity against sensitive strains of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii. However, it failed to achieve fT > 4 µg/mL > 40 to provide activity against strains susceptible to increased exposure in 33.3 and 39.1% patients on the first and the third days, respectively. Modeling and simulation showed that a bolus dose of 500 mg followed by 3-h EI of meropenem 1500 mg Q8H will achieve this target. A bolus of 500 mg followed by an infusion of 2000 mg would be required to achieve fT > 8 µg > 40. Targets of fT > 4 µg/mL = 100 and fT > 8 µg/mL = 100 may be achievable in two-thirds of patients by increasing the frequency of dosing to six hourly (Q6H).

Conclusions

In patients with severe sepsis or septic shock, EI of 1000 mg of meropenem over 3 h administered Q8H is inadequate to provide activity (fT > 4 µg/mL > 40) against strains susceptible to increased exposure, which requires a bolus of 500 mg followed by EI of 1500 mg Q8H. While fT > 8 µg/mL > 40 require escalation of EI dose, fT > 4 µg/mL = 100 and fT > 8 µg/mL = 100 require escalation of both EI dose and frequency.

Advances in the therapy of bacterial bloodstream infections

BACKGROUND

Advances in the diagnostic and therapeutic management of patients with bloodstream infections (BSIs) have been achieved in the last years, improving clinical outcome. However, mortality associated with some pathogens, such as Staphylococcus aureus and Enterococcus spp., is still high. In addition, the spread of antibiotic resistance, mainly among Gram-negative bacteria, reduces treatment options in some circumstances. Therefore, interest in new drugs, combination regimens and optimal dosing schedules is rising.

OBJECTIVES

Our aim is to summarize the current evidence on available antibiotic regimens for patients with bacterial BSI, focusing on drug choice, combination regimens and optimal dosing schedules. We selected bacteria that are difficult to manage because of virulence factors (i.e. methicillin-susceptible S. aureus), tolerance to antibiotic activity (i.e. Enterococcus faecalis), and/or susceptibility patterns (i.e. methicillin-resistant S. aureus, vancomycin-resistant enterococci, carbapenem-resistant Enterobacteriaceae, multidrug-resistant Pseudomonas aeruginosa and carbapenem-resistant Acinetobacter baumannii).

SOURCES

MEDLINE search with English language and publication in the last 5 years as limits.

CONTENT AND IMPLICATIONS

The literature gaps on the use of new drugs, the uncertainties regarding the use of combination regimens, and the need to optimize dosing schedules in some circumstances (e.g. augmented renal clearance, renal replacement therapy, high inoculum BSI sources, and isolation of bacteria showing high MICs) have been revised.

Effect of renal clearance and continuous renal replacement therapy on appropriateness of recommended meropenem dosing regimens in critically ill patients with susceptible life-threatening infections

Background

Meropenem plasma concentration above a pathogen's MIC over the whole dosing interval (100% ƒT>MIC) is a determinant of outcome in severe infections. Significant variability of meropenem pharmacokinetics is reported in ICU patients.

Objectives

To characterize meropenem pharmacokinetics in variable CLCR or renal replacement therapy and assess the appropriateness of recommended regimens for MIC coverage.

Methods

A pharmacokinetic analysis (NONMEM) was conducted with external model validation. Patient characteristics were tested on meropenem clearance estimates, differentiated according to the presence/absence of continuous renal replacement therapy (CRRT, CLCRRT or CLno-CRRT). Simulations evaluated the appropriateness of recommended dosing for achieving 100% fT>MIC in 90% of patients.

Results

A total of 101 patients were studied: median 63 years (range 49-70), 56% male, SAPS II 38 (27-48). 32% had a CLCR >60 mL/min, 49% underwent CRRT and 32% presented severe sepsis or septic shock. A total of 127 pathogens were documented: 76% Gram-negatives, 24% Gram-positives (meropenem MIC90 2 mg/L, corresponding to EUCAST susceptibility breakpoint). Three hundred and eighty plasma and 129 filtrate-dialysate meropenem concentrations were analysed: two-compartment modelling best described the data. Predicted meropenem CLno-CRRT was 59% lower in impaired (CLCR 30 mL/min) compared to normal (CLCR 100 mL/min) renal function. Simulations showed that recommended regimens appropriately cover MIC90 in patients with CLCR <60 mL/min. Patients with CLCR of 60 to <90 mL/min need 6 g/day to achieve appropriate coverage. In patients with CLCR ≥90 mL/min, appropriate exposure is achieved with increased dose, frequency of administration and infusion duration, or continuous infusion.

Conclusions

Recommended meropenem regimens are suboptimal in ICU patients with normal or augmented renal clearance. Modified dosing or infusion modalities achieve appropriate MIC coverage for optimized antibacterial efficacy in meropenem-susceptible life-threatening infections.

Augmented renal clearance is associated with inadequate antibiotic pharmacokinetic/pharmacodynamic target in Asian ICU population: a prospective observational study

Background

Augmented renal clearance (ARC) is common in critically ill patients and could result in subtherapeutic antibiotic concentration. However, data in the Asian population are still lacking. The aim of this study was to explore the incidence and risk factors of ARC and its effect on β-lactam pharmacokinetics/pharmacodynamics (PK/PD) in Asian populations admitted to a medical ICU. In addition, we evaluated the appropriateness of using three estimated glomerular filtration (eGFR) formulas [Cockcroft–Gault (CG), Modification of Diet in Renal Disease (MDRD), and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)] as screening tools.

Methods

We measured 2-, 8-, and 24-hr creatinine clearance (CL_Cr) and calculated eGFR by using three formulas for each. ARC was defined as CL_Cr24hr >130 mL/min/1.73 m². Concentrations at the mid-dosing interval and prior to the next dose were collected if patients received the β-lactam antibiotic of piperacillin/tazobactam, cefepime, and meropenem, to determine the PK/PD index of fT > MIC. Multiple logistic regression analysis was conducted to identify the risk factors for ARC. Pearson correlation coefficient and the Bland and Altman method were applied to assess the accuracy of CL_Cr2hr, CL_Cr8hr, and eGFR for predicting ARC.

Results

Of 100 patients, 46 (46%) manifested ARC. Younger age (<50 years) and lower Sequential Organ Failure Assessment score increased the likelihood of ARC. ARC resulted in a low chance of achieving 50% fT >4MIC (33% vs 75%, p<0.01), 100% fT > MIC (23% vs 69%, p<0.01), and 100% fT >4MIC (3% vs 25%, p<0.02). CL_Cr8hr wielded the best correlation and agreement with CL_Cr24hr. eGFR_CG was the most appropriate screening tool, and the optimal cutoff value for detecting ARC was 130.5 mL/min/1.73 m².

Conclusion

ARC is associated with inadequate β-lactam PK/PD target in Asian ICU.

Pharmacokinetics of meropenem in burn patients with infections caused by Gram-negative bacteria: Are we getting close to the right treatment?

OBJECTIVES

Infections caused by multidrug-resistant Gram-negative bacteria are associated with high mortality. A relevant concern is the efficacy of antibiotic therapy in burn patients in whom pathophysiological changes strongly influence pharmacokinetic (PK) parameters. This study aimed to describe the PK parameters of meropenem in a population of burn patients.

METHODS

Blood samples were collected immediately before and 2 h and 5 h after the start of intravenous drug administration. Plasma meropenem concentrations were determined using an ultra-performance liquid chromatography-photodiode array method.

RESULTS

Seventeen burn patients were enrolled in the study. Thirteen patients (76%) were treated with meropenem for infections byPseudomonas aeruginosa or Acinetobacter baumannii isolated from blood or wounds. Mean C_max, C_min, AUC_0-24, half-life, drug clearance and volume of distribution were 28.9 mg/L, 3.7 mg/L, 280.2 mg h/L, 2.0 h, 19.0 L/h and 44.4 L, respectively. Six patients (35%) achieved a C_min ≥3.3 mg/L and seven patients (41%) achieved a C_max ≥ 28.4 mg/L, whilst nine patients (53%) achieved an AUC_0-24 of >226 mg h/L. Given a minimum inhibitory concentration (MIC) of 0.5 mg/L, all patients satisfied the target AUC/MIC of >125, but when the MIC rises to 2 mg/L (the ECOFF), only five patients reached the desired AUC/MIC. Regarding fT_>MIC at an MIC of 2 mg/L with a 2-h infusion time, 13 patients (76%) achieved the PK target (>75%).

CONCLUSION

These data suggest that a combined 2-h infusion with a higher dosage of meropenem, including a loading dose, may be successful to achieve effective PK parameters.

Optimal infusion rate in antimicrobial therapy explosion of evidence in the last five years

Background

Sporadic studies in antimicrobial therapy have evaluated the effects of infusion rates on therapeutic and economic outcomes, and new findings may challenge the regular infusion regimen.

Methods

Focusing on studies comparing the outcomes of different infusion regimens, the relevant literature was identified by searching PubMed, Web of Science, and Scopus from January 1, 2013 to March 1, 2018. Papers were finally chosen using a PRISMA flowchart.

Results

Antimicrobials with the superiority of prolonged infusion to standard infusion in terms of efficacy and safety include meropenem, doripenem, imipenem, cefepime, ceftazidime, piperacillin/tazobactam, linezolid, and vancomycin. The strategy of concomitantly reducing total daily dose and prolonging infusion time may cause treatment failure (eg, imipenem). Extended infusion of piperacillin/tazobactam has pharmacoeconomic advantage over standard infusion. Prolonged infusion of voriconazole is inferior to standard infusion because of lower efficacy caused by pharmacokinetic changes. Comparable outcomes following standard infusion and continuous infusion were observed with norvancomycin and nafcillin. Factors determining whether prolonged infusion has a benefit over standard infusion include MIC of bacterial pathogens, bacterial density, diagnosis, disease severity, total daily dose, and renal function.

Conclusion

To maximally preserve the effectiveness of current antimicrobials, effective interventions should be implemented to enhance the application of optimal infusion strategies. For reducing nephrotoxicity, prolonged infusion of meropenem is better than conventional infusion in neonates with Gram-negative late-onset sepsis, and continuous infusion of vancomycin is superior to intermittent infusion. For increasing efficacy, prolonged or continuous infusion of time-dependent antimicrobials (eg, meropenem, doripenem, imipenem, cefepime, ceftazidime, piperacillin/tazobactam, linezolid, and vancomycin) is an optimal choice. Nevertheless, such advantages may only be demonstrated in special clinical circumstances and special populations (eg, patients with a sequential organ failure assessment (SOFA) score≥9, respiratory tract infections, urinary or intra-abdominal infections, or infections caused by less susceptible pathogens would benefit from prolonged infusion of piperacillin/tazobactam).

Population Pharmacokinetic Analysis of Meropenem After Intravenous Infusion in Korean Patients With Acute Infections

PURPOSE

The aim of this study was to investigate the population pharmacokinetic (PK) profile of meropenem in Korean patients with acute infections.

METHODS

The study included 37 patients with a creatinine clearance ≤50 or >50 mL/min who received a 500- or 1000-mg dose of meropenem, respectively, infused intravenously over 1 hour every 8 hours. Blood samples were collected before and at 1, 1.5, and 5 hours after the start of the fourth infusion. The population PK analysis was conducted by using nonlinear mixed effect modeling software (NONMEM). Monte-Carlo simulations were performed to identify optimal dosing regimens.

FINDINGS

Thirty-seven subjects completed the study. Meropenem PK variables were well described by using a one-compartment model. The typical values (relative SE) for weight-normalized clearance (CL) and V_d were 0.266 L/h/kg (12.29%) and 0.489 L/kg (11.01%), respectively. Meropenem CL was significantly influenced by the serum creatinine level, which explained 11% of the interindividual CK variability. The proposed equation to estimate meropenem CL in Korean patients was as follows: CL (L/h) = 0.266 × weight × [serum creatinine/0.74]^-1.017_. The simulation results indicate that the current meropenem dosing regimen may be suboptimal in patients infected with normal or augmented renal function.

IMPLICATIONS

Prolonged infusions of meropenem over at least 2 hours should be considered, especially in patients with augmented renal function and those infected with pathogens for which the minimum inhibitory meropenem concentration is >1 μg/mL. Our results suggest an individualized meropenem dosing regimen for patients with abnormal renal function and those infected with pathogens with decreased in vitro susceptibility.

The exploration of population pharmacokinetic model for meropenem in augmented renal clearance and investigation of optimum setting of dose

In recent years, augmented renal clearance (ARC), in which renal function is excessively enhanced, has been reported, and its influence on β-lactam antibiotics has been investigated. In this study, we aimed to determine the optimum population pharmacokinetic model of meropenem in patients with sepsis with ARC, and evaluated dosing regimens based on renal function. Seventeen subjects (6 with ARC and 11 without) were enrolled in this study. Predicted meropenem concentrations were evaluated for bias and precision using the Bland-Altman method. To examine the dosing regimen, Monte Carlo simulation was performed to calculate the cumulative fraction of response (CFR). In patients with ARC, the bias (average of the predicted value and measured value residuals) of models constructed by Crandon et al. (2011), Roberts et al. (2009), and Jaruratanasirikul et al. (2015) were 5.96 μg/mL, 10.91 μg/mL, and 4.41 μg/mL, respectively. Following 2 g meropenem every 8 h (180 min infusion), CFR ≥ 90%, a criterion of success for empirical therapy, was achieved, even with creatinine clearance of 130-250 mL/min. For patients with sepsis and ARC, the model of Jaruratanasirikul et al. showed the highest degree of accuracy and precision and confirmed the efficacy of the meropenem dosing regimen in this patient population.

The use of SWATH to analyse the dynamic changes of bacterial proteome of carbapanemase-producing Escherichia coli under antibiotic pressure

Antibiotic resistance associated with the clinically significant carbapenemases KPC, NDM and OXA-48 in Enterobacteriaceae is emerging as worldwide. In Australia, IMP-producing Enterobacteriaceae are the most prevalent carbapenemase-producing Enterobacteriaceae (CPE). Genomic characteristics of such CPE are well described, but the corresponding proteome is poorly characterised. We have thus developed a method to analyse dynamic changes in the proteome of CPE under antibiotic pressure. Specifically, we have investigated the effect of meropenem at sub-lethal concentrations to develop a better understanding of how antibiotic pressure leads to resistance. Escherichia coli strains producing either NDM-, IMP- or KPC-type carbapenemases were included in this study, and their proteomes were analysed in growth conditions with or without meropenem. The most significant difference in the bacterial proteomes upon the addition of meropenem was triggered amongst NDM-producers and to a lower extent amongst KPC-producers. In particular, HU DNA-binding proteins, the GroEL/GroES chaperonin complex and GrpE proteins were overexpressed. These proteins may thus contribute to the better adaptability of NDM- and KPC-producers to meropenem. A significant meropenem-induced increase in the expression of the outer membrane protein A was only observed in IMP-producers, thus demonstrating that carbapenemase-mediated resistance relies on far more complex mechanisms than simple inactivation of the antibiotic.