Antibiotic dosing in critical illness

Prevalence, risk factors, and outcomes associated with delayed second doses of antibiotics in sepsis at a large academic medical center

Objective

To evaluate the prevalence, risk factors, and clinical impact of delays in second doses of antibiotics in patients with sepsis.

Design

Single-center, retrospective, observational study.

Setting

Large teaching hospital.

Patients

Adult patients who triggered an electronic sepsis alert in the emergency department (ED), received ≥2 doses of vancomycin or an antipseudomonal beta-lactam, and were discharged with an ICD-10 sepsis code.

Methods

We assessed the prevalence of delays in second doses of antibiotics by ≥25% of the recommended dose interval and conducted multivariate regression analyses to assess for risk factors for delays and in-hospital mortality.

Results

The cohort included 449 patients, of whom 123 (27.4%) had delays in second doses. In-hospital death occurred in 31 patients (25.2%) in the delayed group and 71 (21.8%) in the non-delayed group (p = 0.44). On multivariate analysis, only location in a non-ED unit at the time second doses were due was associated with delays (OR 2.75, 95% CI 1.20-6.32). In the mortality model, significant risk factors included malignant tumor, respiratory infection, and elevated Sequential Organ Failure Assessment (SOFA) score but not delayed second antibiotic doses (OR 1.19, 95% CI 0.69-2.05). In a subgroup analysis, delayed second doses were associated with higher mortality in patients admitted to non-intensive care units (ICUs) (OR 4.10, 95% CI 1.32-12.79).

Conclusions

Over a quarter of patients with sepsis experienced delays in second doses of antibiotics. Delays in second antibiotic doses were not associated with higher mortality overall, but an association was observed among patients admitted to non-ICUs.

Optimizing the Use of Beta-Lactam Antibiotics in Clinical Practice: A Test of Time

Despite their limitations, the pharmacokinetics (PK) and pharmacodynamics (PD) indices form the basis for our current understanding regarding antibiotic development, selection, and dose optimization. Application of PK-PD in medicine has been associated with better clinical outcome, suppression of resistance, and optimization of antibiotic consumption. Beta-lactam antibiotics remain the cornerstone for empirical and directed therapy in many patients. The percentage of time of the dosing interval that the free (unbound) drug concentration remains above the minimal inhibitory concentration (MIC) (%fT > MIC) has been considered the PK-PD index that best predicts the relationship between antibiotic exposure and killing for the beta-lactam antibiotics. Time dependence of beta-lactam antibiotics has its origin in the acylation process of the serine active site of penicillin-binding proteins, which subsequently results in bacteriostatic and bactericidal effects during the dosing interval. To enhance the likelihood of target attainment, higher doses, and prolonged infusion strategies, with/or without loading doses, have been applied to compensate for subtherapeutic levels of antibiotics related to PK-PD changes, especially in the early phase of severe sepsis. To minimize resistance and maximize clinical outcome, empirical therapy with a meropenem loading dose followed by high-dose-prolonged infusion should be considered in patients with high inoculum infections presenting as severe (Gram negative) sepsis. Subsequent de-escalation and dosing of beta-lactam antibiotics should be considered as an individualized dynamic process that requires dose adjustments throughout the time course of the disease process mediated by clinical parameters that indirectly assess PK-PD alterations.

Repurposing drugs with specific activity against L-form bacteria

Cell wall deficient “L- form” bacteria are of growing medical interest as a possible source of recurrent or persistent infection, largely because of their complete resistance to cell wall active antibiotics such as β-lactams. Antibiotics that specifically kill L-forms would be of potential interest as therapeutics, but also as reagents with which to explore the role of L-forms in models of recurrent infection. To look for specific anti-L-form antibiotics, we screened a library of several hundred FDA-approved drugs and identified compounds highly selective for L-form killing. Among the compounds identified were representatives of two different classes of calcium channel blockers: dihydropyridines, e.g., manidipine; and diphenylmethylpiperazine, e.g., flunarizine. Mode of action studies suggested that both classes of compound work by decreasing membrane fluidity. This leads to a previously recognized phenotype of L-forms in which the cells can continue to enlarge but fail to divide. We identified a considerable degree of variation in the activity of different representatives of the two classes of compounds, suggesting that it may be possible to modify them for use as drugs for L-form-dependent infections.

Construction and Interpretation of Prediction Model of Teicoplanin Trough Concentration via Machine Learning

Objective

To establish an optimal model to predict the teicoplanin trough concentrations by machine learning, and explain the feature importance in the prediction model using the SHapley Additive exPlanation (SHAP) method.

Methods

A retrospective study was performed on 279 therapeutic drug monitoring (TDM) measurements obtained from 192 patients who were treated with teicoplanin intravenously at the First Affiliated Hospital of Army Medical University from November 2017 to July 2021. This study included 27 variables, and the teicoplanin trough concentrations were considered as the target variable. The whole dataset was divided into a training group and testing group at the ratio of 8:2, and predictive performance was compared among six different algorithms. Algorithms with higher model performance (top 3) were selected to establish the ensemble prediction model and SHAP was employed to interpret the model.

Results

Three algorithms (SVR, GBRT, and RF) with high R² scores (0.676, 0.670, and 0.656, respectively) were selected to construct the ensemble model at the ratio of 6:3:1. The model with R² = 0.720, MAE = 3.628, MSE = 22.571, absolute accuracy of 83.93%, and relative accuracy of 60.71% was obtained, which performed better in model fitting and had better prediction accuracy than any single algorithm. The feature importance and direction of each variable were visually demonstrated by SHAP values, in which teicoplanin administration and renal function were the most important factors.

Conclusion

We firstly adopted a machine learning approach to predict the teicoplanin trough concentration, and interpreted the prediction model by the SHAP method, which is of great significance and value for the clinical medication guidance.

Comparative Plasma and Interstitial Tissue Fluid Pharmacokinetics of Meropenem Demonstrate the Need for Increasing Dose and Infusion Duration in Obese and Non-obese Patients

BACKGROUND AND OBJECTIVES

A quantitative evaluation of the PK of meropenem, a broad-spectrum β-lactam antibiotic, in plasma and interstitial space fluid (ISF) of subcutaneous adipose tissue of obese patients is lacking as of date. The objective of this study was the characterisation of meropenem population pharmacokinetics in plasma and ISF in obese and non-obese patients for identification of adequate dosing regimens via Monte-Carlo simulations.

METHODS

We obtained plasma and microdialysate concentrations after administration of meropenem 1000 mg to 15 obese and 15 non-obese surgery patients from a prospective clinical trial. After characterizing plasma- and microdialysis-derived ISF pharmacokinetics via population pharmacokinetic analysis, we simulated thrice-daily (TID) meropenem short-term (0.5 h), prolonged (3.0 h), and continuous infusions. Adequacy of therapy was assessed by the probability of pharmacokinetic/pharmacodynamic (PK/PD) target attainment (PTA) analysis based on time unbound concentrations exceeded minimum inhibitory concentrations (MIC) on treatment day 1 (%fT _{> MIC}) and the sum of PTA weighted by relative frequency of MIC values for infections by pathogens commonly treated with meropenem. To avoid interstitial tissue fluid concentrations below MIC for the entire dosing interval during continuous infusions, a more conservative PK/PD index was selected (%fT _{> 4 × MIC}).

RESULTS

Adjusted body weight (ABW) and calculated creatinine clearance (CLCR_{CG_ABW}) of all patients (body mass index [BMI] = 20.5-81.5 kg/m²) explained a considerable proportion of the between-patient pharmacokinetic variability (15.1-31.0% relative reduction). The ISF:plasma ratio of %fT _{> MIC} was relatively similar for MIC ≤ 2 mg/L but decreased for MIC = 8 mg/L over ABW = 60-120 kg (0.50-0.20). Steady-state concentrations were 2.68 times (95% confidence interval [CI] = 2.11-3.37) higher in plasma than in ISF, supporting PK/PD targets related to four times the MIC during continuous infusions to avoid suspected ISF concentrations constantly below the MIC. A 3000 mg/24 h continuous infusion was sufficient at MIC = 2 mg/L for patients with CLCR_{CG_ABW} ≤ 100 mL/min and ABW < 90 kg, whereas 2000 mg TID prolonged infusions were adequate for those with CLCR_{CG_ABW} ≤ 100 mL/min and ABW > 90 kg. For MIC = 2 mg/L and %fT_{> MIC} = 95, PTA was adequate in patients over the entire investigated range of body mass and renal function using a 6000 mg continuous infusion. A prolonged infusion of meropenem 2000 mg TID was sufficient for MIC ≤ 8 mg/L and all investigated ABW and CLCR_{CG_ABW} when employing the PK/PD target %fT _{> MIC} = 40. Short-term infusions of 1000 mg TID were sufficient for CLCR_{CG_ABW} ≤ 130 mL/min and distributions of MIC values for Escherichia coli, Citrobacter freundii, and Klebsiella pneumoniae but not for Pseudomonas aeruginosa.

CONCLUSIONS

This analysis indicated a need for higher doses (≥ 2000 mg) and prolonged infusions (≥ 3 h) for obese and non-obese patients at MIC ≥ 2 mg/L. Higher PTA was achieved with prolonged infusions in obese patients and with continuous infusions in non-obese patients.

TRIAL REGISTRATION

EudraCT: 2012-004383-22.

Development of a Model-Informed Dosing Tool to Optimise Initial Antibiotic Dosing-A Translational Example for Intensive Care Units

The prevalence and mortality rates of severe infections are high in intensive care units (ICUs). At the same time, the high pharmacokinetic variability observed in ICU patients increases the risk of inadequate antibiotic drug exposure. Therefore, dosing tailored to specific patient characteristics has a high potential to improve outcomes in this vulnerable patient population. This study aimed to develop a tabular dosing decision tool for initial therapy of meropenem integrating hospital-specific, thus far unexploited pathogen susceptibility information. An appropriate meropenem pharmacokinetic model was selected from the literature and evaluated using clinical data. Probability of target attainment (PTA) analysis was conducted for clinically interesting dosing regimens. To inform dosing prior to pathogen identification, the local pathogen-independent mean fraction of response (LPIFR) was calculated based on the observed minimum inhibitory concentrations distribution in the hospital. A simple, tabular, model-informed dosing decision tool was developed for initial meropenem therapy. Dosing recommendations achieving PTA > 90% or LPIFR > 90% for patients with different creatinine clearances were integrated. Based on the experiences during the development process, a generalised workflow for the development of tabular dosing decision tools was derived. The proposed workflow can support the development of model-informed dosing tools for initial therapy of various drugs and hospital-specific conditions.

Green Strategy–Based Synthesis of Silver Nanoparticles for Antibacterial Applications

Antibiotics have been the nucleus of chemotherapy since their discovery and introduction into the healthcare system in the 1940s. They are routinely used to treat bacterial infections and to prevent infections in patients with compromised immune systems and enhancing growth in livestock. However, resistance to last-resort antibiotics used in the treatment of multidrug-resistant infections has been reported worldwide. Therefore, this study aimed to evaluate green synthesized nanomaterials such as silver nanoparticles (AgNPs) as alternatives to antibiotics. UV-vis spectroscopy surface plasmon resonance peaks for AgNPs were obtained between 417 and 475 nm. An X-ray diffraction analysis generated four peaks for both Prunus africana extract (PAE) and Camellia sinensis extract (CSE) biosynthesized AgNPs positioned at 2θ angles of 38.2°, 44.4°, 64.5°, and 77.4° corresponding to crystal planes (111), (200), (220), and (311), respectively. A dynamic light-scattering analysis registered the mean zeta potential of +6.3 mV and +0.9 mV for PAE and CSE biosynthesized nanoparticles, respectively. Fourier transform infrared spectroscopy spectra exhibited bands corresponding to different organic functional groups confirming the capping of AgNPs by PAE and CSE phytochemicals. Field emission scanning electron microscopy imaging showed that AgNPs were spherical with average size distribution ranging from 10 to 19 nm. Biosynthesized AgNPs exhibited maximum growth inhibitory zones of 21 mm with minimum inhibitory concentration and minimum bactericidal concentration of 125 and 250 μg/ml, respectively, against carbapenem-resistant bacteria.

Liver function, quantified by the LiMAx test, as a predictor for the clinical outcome of critically ill patients treated with linezolid

BACKGROUND

Critically ill patients commonly suffer from infections that require antimicrobial therapy. In previous studies, liver dysfunction was shown to have an essential impact on the dose selection in these patients. This pilot study aims to assess the influence of liver dysfunction, measured by the novel LiMAx test, on clinical outcomes in critically ill patients treated with linezolid.

METHODS

Twenty-nine critically ill patients were included and treated with linezolid. Indications for linezolid therapy were secondary or tertiary peritonitis (46.7%), bloodstream infection (6.7%) and 46.7% were other infections with gram-positive bacteria. Linezolid Cmin, maximal liver function capacity (LiMAx test) and plasma samples were collected while linezolid therapy was in a steady-state condition. Furthermore, potential factors for the clinical outcome were investigated using logistic regression analysis. Clinical cure was defined as the resolution or significant improvement of clinical symptoms without using additional antibiotic therapy or intervention.

RESULTS

Cured patients presented lower median linezolid Cmin yet a significantly higher mean LiMAx-value compared to the clinical failure group (1.9 mg/L vs. 5.1 mg/L) (349 μg/kg/h vs. 131 μg/kg/h). In the logistic regression model, LiMAx < 178 μg/kg/h was the only independent predictor of clinical failure with a sensitivity of 77% and specificity of 93%.

CONCLUSIONS

The LiMAx test predicts clinical failure more precisely than linezolid trough levels in critically ill surgical patients. Therefore liver failure may have a stronger impact on the outcome of critically ill surgical patients than low linezolid Cmin. While linezolid Cmin failed to predict patient's outcome, LiMAx results were the only independent predictor of clinical failure.

Loading dose and efficacy of continuous or extended infusion of beta-lactams compared with intermittent administration in patients with critical illnesses: A subgroup meta-analysis and meta-regression analysis

WHAT IS KNOWN AND OBJECTIVE

The role of continuous/extended beta-lactam infusions (CEIs) in improving clinical outcomes among critically ill patients remains controversial. Therefore, we aimed to compare the clinical efficacy of CEI versus intermittent administration (IA) of beta-lactams by performing a systematic review and meta-analysis.

METHODS

PubMed, the Cochrane Library and Embase were searched from inception until December 2018 for studies comparing clinical outcomes of CEI versus IA in critically ill patients. The meta-analysis included 18 randomized controlled trials (RCTs) and 13 non-RCTs.

RESULTS AND DISCUSSION

For CEI versus IA, the summary relative risk (RR) for overall mortality and clinical cure was 0.82 (95% confidence interval [CI]: 0.72-0.94) and 1.31 (95% CI: 1.15-1.49), respectively. Subgroup and meta-regression analyses of the loading dose revealed a significantly increased clinical cure rate in the loading-dose group (RR: 1.44, 95% CI: 1.22-1.69), which remained significant after adjustments for beta-lactam type, and association between clinical cure and loading dose for clinical cure (RR: 1.47, 95% CI: 1.20-1.80; p = .001). Subgroup analysis of administration type indicated that both groups had low mortality and high clinical cure rates; however, the heterogeneity analysis did not support an association across continuous infusion and extended infusion groups. Subgroup analysis of the Acute Physiology and Chronic Health Evaluation (APACHE) score was conducted; according to APACHE scores ≥ 16, overall mortality and clinical cure significantly differed between CEI and IA.

WHAT IS NEW AND CONCLUSION

CEIs with loading-dose treatment may significantly improve the clinical outcomes in critically ill sepsis or septic shock patients.

Delays in antibiotic redosing: Association with inpatient mortality and risk factors for delay

OBJECTIVE

Although timely administration of antibiotics has an established benefit in serious bacterial infection, the majority of studies evaluating antibiotic delay focus only on the first dose. Recent evidence suggests that delays in redosing may also be associated with worse clinical outcome. In light of the increasing burden of boarding in Emergency Departments (ED) and subsequent need to redose antibiotic in the ED, we examined the association between delayed second antibiotic dose administration and mortality among patients admitted from the ED with a broad array of infections and characterized risk factors associated with delayed second dose administration.

METHODS

We performed a retrospective cohort study of patients admitted through five EDs in a single healthcare system from 1/2018 through 12/2018. Our study included all patients, aged 18 years or older, who received two intravenous antibiotic doses within a 30-h period, with the first dose administered in the ED. Patients with end stage renal disease, cirrhosis and extremes of weight were excluded due to a lack of consensus on antibiotic dosing intervals for these populations. Delay was defined as administration of the second dose at a time-point greater than 125% of the recommended interval. The primary outcome was in-hospital mortality.

RESULTS

A total of 5605 second antibiotic doses, occurring during 4904 visits, met study criteria. Delayed administration of the second dose occurred during 21.1% of visits. After adjustment for patient characteristics, delayed second dose administration was associated with increased odds of in-hospital mortality (OR 1.50, 95%CI 1.05-2.13). Regarding risk factors for delay, every one-hour increase in allowable compliance time was associated with a 18% decrease in odds of delay (OR 0.82 95%CI 0.75-0.88). Other risk factors for delay included ED boarding more than 4 h (OR 1.47, 95%CI 1.27-1.71) or a high acuity presentation as defined by emergency severity index (ESI) (OR 1.54, 95%CI 1.30-1.81 for ESI 1-2 versus 3-5).

CONCLUSIONS

Delays in second antibiotic dose administration were frequent in the ED and early hospital course, and were associated with increased odds of in-hospital mortality. Several risk factors associated with delays in second dose administration, including ED boarding, were identified.

Meropenem use and therapeutic drug monitoring in clinical practice: a literature review

WHAT IS KNOWN AND OBJECTIVE

Meropenem, a carbapenem antibiotic, is widely prescribed for the treatment of life-threatening infections. The main parameter associated with its therapeutic success is the percentage of time that the levels remain above the minimum inhibitory concentration. Inadequate levels of meropenem can lead to therapeutic failure and increase the possibility of microbial resistance. The employment of strategies involving dose regimens and drug pharmacodynamics has become increasingly important to optimize therapies. In the present study, we conducted a review with the purpose of assembling information about the clinical use of meropenem and therapeutic drug monitoring.

METHODS

A literature review emphasizing the application of therapeutic drug monitoring (TDM) of meropenem in clinical practice has been done. To identify articles related to the topic, we performed a standardized search from January 21, 2020 to December 21, 2020, using specific descriptors in PubMed, Lilacs and Embase.

RESULTS AND DISCUSSION

In total, 35 studies were included in the review. The daily dose of meropenem commonly ranged from 3 to 6 g/day. Critically ill patients and those with impaired renal function appear to be the most suitable patients for the application of meropenem TDM, in order to guide therapy. We observed that most of the studies recommend TDM and that, in nine locations, the TDM of meropenem and of other beta-lactams is a routine practice. TDM data can help to maximize the clinical outcomes of the treatment with meropenem. It can also improve the patient care by providing suitable levels of meropenem, guiding the most appropriate dose regimens, which is the main parameter associated with therapeutic success.

WHAT IS NEW AND CONCLUSION

The findings from this review suggest that the therapeutic monitoring of meropenem can be beneficial, since it adjusts the treatment and aids clinical outcomes. It does so by indicating the appropriate dosage and preventing failure, toxicity and possible antimicrobial resistance. The multidisciplinary effort, basic knowledge and communication among the medical team are also essential.

Optimising efficacy of antibiotics against systemic infection by varying dosage quantities and times

Mass production and use of antibiotics has led to the rise of resistant bacteria, a problem possibly exacerbated by inappropriate and non-optimal application. Antibiotic treatment often follows fixed-dose regimens, with a standard dose of antibiotic administered equally spaced in time. But are such fixed-dose regimens optimal or can alternative regimens be designed to increase efficacy? Yet, few mathematical models have aimed to identify optimal treatments based on biological data of infections inside a living host. In addition, assumptions to make the mathematical models analytically tractable limit the search space of possible treatment regimens (e.g. to fixed-dose treatments). Here, we aimed to address these limitations by using experiments in a Galleria mellonella (insect) model of bacterial infection to create a fully parametrised mathematical model of a systemic Vibrio infection. We successfully validated this model with biological experiments, including treatments unseen by the mathematical model. Then, by applying artificial intelligence, this model was used to determine optimal antibiotic dosage regimens to treat the host to maximise survival while minimising total antibiotic used. As expected, host survival increased as total quantity of antibiotic applied during the course of treatment increased. However, many of the optimal regimens tended to follow a large initial ‘loading’ dose followed by doses of incremental reductions in antibiotic quantity (dose ‘tapering’). Moreover, application of the entire antibiotic in a single dose at the start of treatment was never optimal, except when the total quantity of antibiotic was very low. Importantly, the range of optimal regimens identified was broad enough to allow the antibiotic prescriber to choose a regimen based on additional criteria or preferences. Our findings demonstrate the utility of an insect host to model antibiotic therapies in vivo and the approach lays a foundation for future regimen optimisation for patient and societal benefits.

Research into optimal antibiotic use to improve efficacy is far behind that of cancer care, where personalised treatment is common. The integration of mathematical models with biological observations offers hope to optimise antibiotic use, and in this present study an in vivo insect model of systemic Vibrio infection was used for the first time to determine critical model parameters for optimal antibiotic treatment. By this approach, the optimal regimens tended to result from a large initial ‘loading’ dose followed by subsequent doses of incremental reductions in antibiotic quantity (dose ‘tapering’). The approach and findings of this study opens a new avenue towards optimal application of our precious antibiotic arsenal and may lead to more effective treatment regimens for patients, thus reducing the health and economic burdens associated with bacterial infections. Importantly, it can be argued that until we understand how to use a single antibiotic optimally, it is unlikely we will identify optimal ways to use multiple antibiotics simultaneously.

Antimicrobial Therapy in Septic Shock Is Conservative During Resuscitation and Maintenance Phases

Background: Maximal dosing of early antimicrobials with high loading and maintenance doses may optimize pharmacokinetic parameters to achieve and maintain therapeutic concentrations at the site of infection in septic shock. Little is known about the current practice of early antimicrobial dosing in septic shock. Objective: To characterize early antimicrobial dosing in patients in the resuscitation phase of septic shock. Methods: This retrospective cohort study included patients admitted to the medical intensive care unit (ICU) with septic shock. The primary outcome was the percentage of early antibiotic orders that were maximal or conservative during the resuscitation (0 to 48 hours) phase based on predefined dosing criteria. The secondary outcomes were the correlations of different dosing strategies on hospital length of stay (LOS), ICU LOS, and hospital mortality. Results: This study evaluated 161 patients and 692 antibiotic orders; 504 (72.8%) of the orders during the resuscitation phase were conservative. There were no differences in mortality (odds ratio = 0.66; 95% confidence interval = 0.35-1.25; P = .20), hospital LOS (median = 20 [interquartile range (IQR) = 10-34] vs 19 [IQR = 11-32] days; P = .93), or ICU LOS (median = 8 [IQR = 5-16] vs 9 [IQR = 5-15] days; P = .63) between maximal and conservative dosing groups, respectively, in the resuscitation phase. Limitations of this study included the use of institution-specific antimicrobial dosing guidelines and its retrospective nature. Conclusions: Early antibiotic dosing is conservative for a majority of patients in septic shock. Future studies are needed to evaluate the impact of dosing strategy on patient-centered outcomes in septic shock.

Paclitaxel, Imatinib and 5-Fluorouracil Increase the Unbound Fraction of Flucloxacillin In Vitro

Flucloxacillin (FLU), an isoxazolyl penicillin, is widely used for the treatment of different bacterial infections in intensive care units (ICU). Being highly bound to plasma proteins, FLU is prone to drug-drug interactions (DDI) when administered concurrently with other drugs. As FLU is binding to both Sudlow’s site I and site II of human serum albumin (HSA), competitive and allosteric interactions with other drugs, highly bound to the same sites, seem conceivable. Knowledge about interaction(s) of FLU with the widely used anticancer agents paclitaxel (PAC), imatinib (IMA), and 5-fluorouracil (5-FU is scarce. The effects of the selected anticancer agents on the unbound fraction of FLU were evaluated in pooled plasma as well as in HSA and α-1-acid glycoprotein (AGP) samples, the second major drug carrier in plasma. FLU levels in spiked samples were analyzed by LC-MS/MS after ultrafiltration. Significant increase in FLU unbound fraction was observed when in combination with PAC and IMA and to a lesser extent with 5-FU. Furthermore, significant binding of FLU to AGP was observed. Collectively, this is the first study showing the binding of FLU to AGP as well as demonstrating a significant DDI between PAC/IMA/5-FU and FLU.

Population Pharmacokinetics and Dosage Optimization of Teicoplanin in Children With Different Renal Functions

Objective

The purposes of our study were to investigate the population pharmacokinetics of teicoplanin in Chinese children with different renal functions and to propose the appropriate dosing regimen for these pediatric patients.

Methods

We performed a prospective pharmacokinetic research on children aged 0-10 years, with different renal functions. The population pharmacokinetics model of teicoplanin was developed using NLME program. The individualized optimal dosage regimen was proposed on the basis of the obtained population pharmacokinetics parameters.

Results

To achieve the target trough level of 10-30 mg/L, optimal dosing regimen for children with different renal functions are predicted as follows based on the population PK simulations: children with moderate renal insufficiency need three loading doses of 6 mg/kg q12h followed by a maintenance dose of 5 mg/kg qd; children with mild renal insufficiency require three loading doses of 12 mg/kg q12h followed by a maintenance dose of 8 mg/kg qd; children with normal or augmented renal function should be given three loading doses of 12 mg/kg q12h followed by a maintenance doses of 10 mg/kg qd.

Conclusion

The first study on the population pharmacokinetics of teicoplanin in Chinese children with different renal functions was performed. Individualized dosing regimen was recommended for different renal function groups based on population PK model prediction.

Treatment and outcomes of Enterococcus faecium bloodstream infections in solid organ transplant recipients

Optimal antimicrobial therapy for Enterococcus faecium bloodstream infection (EFBSI) in the solid organ transplant (SOT) population is not well defined. The purpose of this study was to describe the pharmacotherapy and outcomes of EFBSI in SOT patients. This was a single-center retrospective cohort of SOT patients with EFBSI from 2013 to 2019. Susceptibility testing was performed with Vitek^® 2 or Etest. Estimates of optimal DAP pharmacokinetic/pharmacodynamic exposures (dose <10 mg/kg, fAUC/MIC >27.4) were made from previously established literature and equations. Fifty-one unique cases were included in the analysis. The median age was 61 years and liver (64%), intestinal (19%), and kidney (12%) were the most common organs transplanted. Most patients had indwelling central lines (75%) at the time of bacteremia; intra-abdominal abscesses/fluid collections were present in 44% of patients and 8% had endocarditis. Nineteen (37%) patients had polymicrobial infections. The most common definitive antimicrobial regimens were as follows: DAP plus beta-lactam (46%), DAP monotherapy (18%), and LZD (25%). Of the 33 patients that received DAP, 21% of E faecium isolates developed DAP resistance. 30-day mortality was 25% overall but higher in patients who received an initial DAP dose <10 mg/kg (43% vs 13%). Vancomycin-resistance, severity of illness, neutropenia, and source control were also associated with mortality. Inadequate DAP dosing for EFBSI may be associated with mortality in the SOT population. Larger, controlled analyses are necessary to determine the impact of optimized pharmacodynamics in this population.

Trends in mathematical modeling of host-pathogen interactions

Pathogenic microorganisms entail enormous problems for humans, livestock, and crop plants. A better understanding of the different infection strategies of the pathogens enables us to derive optimal treatments to mitigate infectious diseases or develop vaccinations preventing the occurrence of infections altogether. In this review, we highlight the current trends in mathematical modeling approaches and related methods used for understanding host-pathogen interactions. Since these interactions can be described on vastly different temporal and spatial scales as well as abstraction levels, a variety of computational and mathematical approaches are presented. Particular emphasis is placed on dynamic optimization, game theory, and spatial modeling, as they are attracting more and more interest in systems biology. Furthermore, these approaches are often combined to illuminate the complexities of the interactions between pathogens and their host. We also discuss the phenomena of molecular mimicry and crypsis as well as the interplay between defense and counter defense. As a conclusion, we provide an overview of method characteristics to assist non-experts in their decision for modeling approaches and interdisciplinary understanding.

Differences in Vancomycin Clearance between Trauma and Medical Intensive Care Unit Patients

Background

To identify the differences in the vancomycin pharmacokinetics between multiple trauma patients and medically ill patients in the intensive care unit (ICU) stratified by the use of continuous renal replacement therapy (CRRT), and the factors affecting vancomycin clearance (CL_van).

Materials and Methods

All the included patients received at least three consecutive doses of vancomycin, then, therapeutic drug monitoring was conducted. Patients' serum vancomycin trough levels and other clinical variables were identified retrospectively. The vancomycin pharmacokinetics and associated factors were compared and analyzed between trauma ICU (TICU) and medical ICU (MICU) patients.

Results

In the non-dialyzed group, the CL_van was higher among the TICU patients than the MICU patients. However, in the continuous renal replacement therapy group, there was no significant difference in the CL_van between the multiple trauma and medically ill patients. The only factor associated with CL_van in the non-dialyzed group was creatinine clearance; none of the factors was associated with CL_van in the CRRT group.

Conclusion

In the case of non-dialyzed patients in the TICU, vancomycin dosages must be adjusted, depending on the patient's actual body weight changes. In the case of patients undergoing CRRT in both ICUs, vancomycin can be infused with fixed doses regardless of the patients' characteristics.

Molecular Imaging: a Novel Tool To Visualize Pathogenesis of Infections In Situ

Molecular imaging is an emerging technology that enables the noninvasive visualization, characterization, and quantification of molecular events within living subjects. Positron emission tomography (PET) is a clinically available molecular imaging tool with significant potential to study pathogenesis of infections in humans.

Molecular imaging is an emerging technology that enables the noninvasive visualization, characterization, and quantification of molecular events within living subjects. Positron emission tomography (PET) is a clinically available molecular imaging tool with significant potential to study pathogenesis of infections in humans. PET enables dynamic assessment of infectious processes within the same subject with high temporal and spatial resolution and obviates the need for invasive tissue sampling, which is difficult in patients and generally limited to a single time point, even in animal models. This review presents current state-of-the-art concepts on the application of molecular imaging for infectious diseases and details how PET imaging can facilitate novel insights into infectious processes, ongoing development of pathogen-specific imaging, and simultaneous in situ measurements of intralesional antimicrobial pharmacokinetics in multiple compartments, including privileged sites. Finally, the potential clinical applications of this promising technology are also discussed.

Noninvasive 11C-rifampin positron emission tomography reveals drug biodistribution in tuberculous meningitis

Tuberculous meningitis (TBM) is a devastating form of tuberculosis (TB), and key TB antimicrobials, including rifampin, have restricted brain penetration. A lack of reliable data on intralesional drug biodistribution in infected tissues has limited pharmacokinetic (PK) modeling efforts to optimize TBM treatments. Current methods to measure intralesional drug distribution rely on tissue resection, which is difficult in humans and generally limited to a single time point even in animals. In this study, we developed a multidrug treatment model in rabbits with experimentally induced TBM and performed serial noninvasive dynamic ¹¹C-rifampin positron emission tomography (PET) over 6 weeks. Area under the curve brain/plasma ratios were calculated using PET and correlated with postmortem mass spectrometry. We demonstrate that rifampin penetration into infected brain lesions is limited, spatially heterogeneous, and decreases rapidly as early as 2 weeks into treatment. Moreover, rifampin concentrations in the cerebrospinal fluid did not correlate well with those in the brain lesions. First-in-human ¹¹C-rifampin PET performed in a patient with TBM confirmed these findings. PK modeling predicted that rifampin doses (≥30 mg/kg) were required to achieve adequate intralesional concentrations in young children with TBM. These data demonstrate the proof of concept of PET as a clinically translatable tool to noninvasively measure intralesional antimicrobial distribution in infected tissues.

Kinetic Driver of Antibacterial Drugs against Plasmodium falciparum and Implications for Clinical Dosing

Antibacterial drugs are an important component of malaria therapy. We studied the interactions of clindamycin, tetracycline, chloramphenicol, and ciprofloxacin against Plasmodium falciparum under static and dynamic conditions. In microtiter plate assays (static conditions), and as expected, parasites displayed the delayed death response characteristic for apicoplast-targeting drugs. However, rescue by isopentenyl pyrophosphate was variable, ranging from 2,700-fold for clindamycin to just 1.7-fold for ciprofloxacin, suggesting that ciprofloxacin has targets other than the apicoplast. We also examined the pharmacokinetic-pharmacodynamic relationships of these antibacterials in an in vitro glass hollow-fiber system that exposes parasites to dynamically changing drug concentrations. The same total dose and area under the concentration-time curve (AUC) of the drug was deployed either as a single short-lived high peak (bolus) or as a constant low concentration (infusion). All four antibacterials were unambiguously time-driven against malaria parasites: infusions had twice the efficacy of bolus regimens, for the same AUC. The time-dependent efficacy of ciprofloxacin against malaria is in contrast to its concentration-driven action against bacteria. In silico simulations of clinical dosing regimens and resulting pharmacokinetics revealed that current regimens do not maximize time above the MICs of these drugs. Our findings suggest that simple and rational changes to dosing may improve the efficacy of antibacterials against falciparum malaria.

The Role of Antibiotic Stewardship in Promoting Appropriate Antibiotic Use

Antibiotics are one of the most significant medical discoveries in human history. The widespread use of antibiotics has resulted in the emergence of antibiotic-resistant pathogens. This fact, coupled with the paucity of new antibiotic developments, has spurred efforts to combat antibiotic resistance. One of the most critical components of these efforts is antibiotic stewardship, a multidisciplinary endeavor, employing a collection of interventions in a variety of health care settings with the aim of promoting appropriate utilization of antibiotics. This article describes antibiotic stewardship programs and key practices used to minimize the development and spread of antibiotic-resistant pathogens including the optimization of antibiotic pharmacokinetics and pharmacodynamics, the application of rapid diagnostic tools, and the use of computerized provider order entry tools.

Development of a dosing algorithm for meropenem in critically ill patients based on a population pharmacokinetic/pharmacodynamic analysis

Effective antibiotic dosing is vital for therapeutic success in critically ill patients. This work aimed to develop an algorithm to identify appropriate meropenem dosing in critically ill patients. Population pharmacokinetic (PK) modelling was performed in NONMEM®7.3 based on densely sampled meropenem serum samples (n_patients = 48; n_samples = 1376) and included a systematic analysis of 27 pre-selected covariates to identify factors influencing meropenem exposure. Using Monte Carlo simulations newly considering the uncertainty of PK parameter estimates, standard meropenem dosing was evaluated with respect to attainment of the pharmacokinetic/pharmacodynamic (PK/PD) target and was compared with alternative infusion regimens (short-term, prolonged, continuous; daily dose, 2000-6000 mg). Subsequently, a dosing algorithm was developed to identify appropriate dosing regimens. The two-compartment population PK model included three factors influencing meropenem pharmacokinetics: the Cockcroft-Gault creatinine clearance (CLCR_CG) on meropenem clearance; and body weight and albumin on the central and peripheral volume of distribution, respectively; of these, only CLCR_CG was identified as a vital influencing factor on PK/PD target attainment. A three-level dosing algorithm was developed (considering PK parameter uncertainty), suggesting dosing regimens depending on renal function and the level (L) of knowledge about the infecting pathogen (L1, pathogen unknown; L2, pathogen known; L3_(-MIC), pathogen and susceptibility known; L3_(+MIC), MIC known). Whereas patients with higher CLCR_CG and lower pathogen susceptibility required mainly intensified dosing regimens, lower than standard doses appeared sufficient for highly susceptible pathogens. In conclusion, a versatile meropenem dosing algorithm for critically ill patients is proposed, indicating appropriate dosing regimens based on patient- and pathogen-specific information.

A critical review of HPLC-based analytical methods for quantification of Linezolid

Linezolid is a synthetic antimicrobial agent belonging to the oxazolidinone class. Since its approval in the year 2000 until now, linezolid remains the main representative drug for the oxazolidinone class of drugs, which is used in therapy due to its unique mode of action, which involves inhibition of protein synthesis. As linezolid holds great importance in antimicrobial therapy, it is necessary to compile the various analytical methods that have been reported in the literature for its analysis. Analytical techniques used for pharmaceutical analyses and therapeutic drug monitoring play an important role in comprehending the aspects regarding bioavailability, bioequivalence, and therapeutic monitoring during patient follow-ups. Even though linezolid has had the approval for clinical use for more than 18 years now, most of the analytical methods for its determination reported in the scientific literature are the ones which utilize HPLC. Therefore, the present review provides a summary of the HPLC-based methods used in the determination and quantification of linezolid in different matrices since the time of its discovery.

Vancomycin Removal During High-Volume Peritoneal Dialysis in Acute Kidney Injury Patients: A Prospective Cohort Clinical Study

Introduction

Vancomycin pharmacokinetic data in patients with acute kidney injury (AKI) on high-volume peritoneal dialysis (HVPD) are lacking. The aims were to study the pharmacokinetics of i.v. vancomycin in patients with AKI treated by HVPD who received an i.v. dose of vancomycin (15–20 mg/kg), to determine the vancomycin removal, and to establish vancomycin dosing and evaluation pharmacokinetics target attainment achievement for the empirical treatment of patients with AKI treated by HVPD.

Methods

Vancomycin was administered 1 hour before dialysis start. Samples of all dialysate were collected for a 24-hour period. Blood samples were collected after 1, 2, 4, and 24 hours of therapy. Vancomycin concentrations were determined using a liquid chromatographic (high-performance liquid chromatography)–fluorescence method. Pharmacokinetic calculations were completed assuming a 1-compartment model.

Results

Ten patients completed the study. The mean vancomycin dose administered was 18.0 ± 2.95 mg/kg (14.7–21.8 mg/kg) on the day of study (first day) and the mean percentage of vancomycin removal by HVPD was 21.7% ± 2.2% (16%–29%). Peritoneal clearance was 8.1 ± 2.2 ml/min (5.3–12 ml/min). The serum vancomycin half-life was 71.2 ± 24.7 hours (42–110 hours) during HVPD session, the maximum serum concentration was 26.2 ± 3.5 mg/l, which occurred 1 hour after vancomycin administration and HVPD start. Area under the curve (AUC)0–24/minimum inhibitory concentration (MIC) ratio ≥400 was achieved in all patients when MIC = 1 mg/l was considered.

Conclusion

HVPD removes considerable amounts of vancomycin in septic patients with AKI. Administration of 18 mg/kg vancomycin each 48 to 72 hours in patients with AKI undergoing HVPD was required to reach and maintain therapeutic concentrations.

Linezolid: a review of its properties, function, and use in critical care

Linezolid can be considered as the first member of the class of oxazolidinone antibiotics. The compound is a synthetic antibiotic that inhibits bacterial protein synthesis through binding to rRNA. It also inhibits the creation of the initiation complex during protein synthesis which can reduce the length of the developed peptide chains, and decrease the rate of reaction of translation elongation. Linezolid has been approved for the treatment of infections caused by vancomycin-resistant Enterococcus faecium, hospital-acquired pneumonia caused by Staphylococcus aureus, complicated skin and skin structure infections (SSSIs), uncomplicated SSSIs caused by methicillin-susceptible S. aureus or Streptococcus pyogenes, and community-acquired pneumonia caused by Streptococcus pneumoniae. Analysis of high-resolution structures of linezolid has demonstrated that it binds a deep cleft of the 50S ribosomal subunit that is surrounded by 23S rRNA nucleotides. Mutation of 23S rRNA was shown to be a linezolid resistance mechanism. Besides, mutations in specific regions of ribosomal proteins uL3 and uL4 are increasingly associated with linezolid resistance. However, these proteins are located further away from the bound drug. The methicillin-resistant S. aureus and vancomycin-resistant enterococci are considered the most common Gram-positive bacteria found in intensive care units (ICUs), and linezolid, as an antimicrobial drug, is commonly utilized to treat infected ICU patients. The drug has favorable in vitro and in vivo activity against the mentioned organisms and is considered as a useful antibiotic to treat infections in the ICU.

Prolonged antibiotic prophylaxis after thoracoabdominal esophagectomy does not reduce the risk of pneumonia in the first 30 days: a retrospective before-and-after analysis

PURPOSE

Thoracoabdominal esophageal resection for malignant disease is frequently associated with pulmonary infection. Whether prolonged antibiotic prophylaxis beyond a single perioperative dose is advantageous in preventing pulmonary infection after thoracoabdominal esophagectomy remains unclear.

METHODS

In this retrospective before-and-after analysis, 173 patients between January 2009 and December 2014 from a prospectively maintained database were included. We evaluated the effect of a 5-day postoperative course of moxifloxacin, which is a frequently used antimicrobial agent for pneumonia, on the incidence of pulmonary infection and mortality after thoracoabdominal esophagectomy.

RESULTS

104 patients received only perioperative antimicrobial prophylaxis (control group) and 69 additionally received a 5-day postoperative antibiotic therapy with moxifloxacin (prolonged-course). 22 (12.7%) of all patients developed pneumonia within the first 30 days after surgery. No statistically significant differences were seen between the prolonged group and control group in terms of pneumonia after 7 (p = 0.169) or 30 days (p = 0.133), detected bacterial species (all p > 0.291) and 30-day mortality (5.8 vs 10.6%, p = 0.274).

CONCLUSION

A preemptive 5-day postoperative course of moxifloxacin does not reduce the incidence of pulmonary infection and does not improve mortality after thoracoabdominal esophagectomy.

A Multicentric, Prospective, Observational Antibacterial Utilization Study in Indian Tertiary Referral Centers

Rationale

Antibacterials are largely prescribed to the intensive care unit (ICU) patients due to high prevalence of infections. However, appropriate use of antibacterials is imperative; since the misuse of antibacterials increases antibacterial resistance and ultimately, it has negative impact on health care and economic system. Hence, continuous antibacterials prescription assessments are very important to judge and improve prescription patterns. The present work was carried out at public and private hospitals to assess the differences in antibacterial prescribing pattern.

Methods

The present study was conducted at three public and two private hospitals over the period of 14 months. Demographic and drug use details were captured daily from patients admitted to medical ICUs to assess the World Health Organization indicators.

Results

A total of 700 patients were enrolled across the five centers (140 per center), among them 424 were male and 276 were female. Average number of drugs and antibacterials prescribed at public hospitals are significantly higher than the private hospital. However, percentage of antibacterial agents prescribed at public hospitals was significantly lower than the private hospitals (P = 0.0381). Private hospitals had significantly lower percentage of antibacterial agents prescribed by generic name (P < 0.0001). Differences in change of antibacterial agents required were not statistically significantly different (P = 0.1888); however, significant difference was observed in percentage of patients who received antibacterial treatment as per sensitivity pattern (P = 0.0385) between public and private hospitals. Significantly higher mortality was observed in public hospitals compared to private hospitals (<0.0001).

Conclusions

More generic prescriptions and more number of prescriptions as per the sensitivity pattern are required at each public and private hospital.

Co-Amorphous Formation of High-Dose Zwitterionic Compounds with Amino Acids To Improve Solubility and Enable Parenteral Delivery

Solubilization of parenteral drugs is a high unmet need in both preclinical and clinical drug development. Recently, co-amorphous drug formulation has emerged as a new strategy to solubilize orally dosed drugs. The aim of the present study is to explore the feasibility of using the co-amorphous strategy to enable the dosing of parenteral zwitterionic drugs at a high concentration. A new screening procedure was established with solubility as the indicator for co-amorphous co-former selection, and lyophilization was established as the method for co-amorphous formulation preparation. Various amino acids were screened, and tryptophan was found to be the most powerful in improving the solubility of ofloxacin when lyophilized with ofloxacin at a 1:1 weight ratio, with more than 10 times solubility increase. X-ray powder diffraction showed complete amorphization of both components, and an elevated T_g compared with the theoretical value was observed in differential scanning calorimetry. Fourier transform infrared spectroscopy revealed that hydrogen bonding and π-π stacking were possibly involved in the formation of a co-amorphous system in the solid state. Further solution-state characterization revealed the involvement of ionic interactions and π-π stacking in maintaining a high concentration of ofloxacin in solution. Furthermore, co-amorphous ofloxacin/tryptophan at 1:1 weight ratio was both physically and chemically stable for at least 2 months at 40 °C/75% RH. Lastly, the same screening procedure was validated with two more zwitterionic compounds, showing its promise as a routine screening methodology to solubilize and enable the parenteral delivery of zwitterionic compounds.

Delayed Second Dose Antibiotics for Patients Admitted From the Emergency Department With Sepsis: Prevalence, Risk Factors, and Outcomes

OBJECTIVE

1) Determine frequency and magnitude of delays in second antibiotic administration among patients admitted with sepsis; 2) Identify risk factors for these delays; and 3) Exploratory: determine association between delays and patient-centered outcomes (mortality and mechanical ventilation after second dose).

DESIGN

Retrospective, consecutive sample sepsis cohort over 10 months.

SETTING

Single, tertiary, academic medical center.

PATIENTS

All patients admitted from the emergency department with sepsis or septic shock (defined: infection, ≥ 2 systemic inflammatory response syndrome criteria, hypoperfusion/organ dysfunction) identified by a prospective quality initiative.

EXCLUSIONS

less than 18 years old, not receiving initial antibiotics in the emergency department, death before antibiotic redosing, and patient refusing antibiotics.

INTERVENTIONS

We determined first-to-second antibiotic time and delay frequency. We considered delay major for first-to-second dose time greater than or equal to 25% of the recommended interval. Factors of interest were demographics, recommended interval length, comorbidities, clinical presentation, location at second dose, initial resuscitative care, and antimicrobial activity mechanism.

MEASUREMENTS AND MAIN RESULTS

Of 828 sepsis cases, 272 (33%) had delay greater than or equal to 25%. Delay frequency increased dose dependently with shorter recommended interval: 11 (4%) delays for 24-hour intervals (median time, 18.52 hr); 31 (26%) for 12-hour intervals (median, 10.58 hr); 117 (47%) for 8-hour intervals (median, 9.60 hr); and 113 (72%) for 6-hour intervals (median, 9.55 hr). In multivariable regression, interval length significantly predicted major delay (12 hr: odds ratio, 6.98; CI, 2.33-20.89; 8 hr: odds ratio, 23.70; CI, 8.13-69.11; 6 hr: odds ratio, 71.95; CI, 25.13-206.0). Additional independent risk factors were inpatient boarding in the emergency department (odds ratio, 2.67; CI, 1.74-4.09), initial 3-hour sepsis bundle compliance (odds ratio, 1.57; CI, 1.07-2.30), and older age (odds ratio, 1.16 per 10 yr, CI, 1.01-1.34). In the exploratory multivariable analysis, major delay was associated with increased hospital mortality (odds ratio, 1.61; CI, 1.01-2.57) and mechanical ventilation (odds ratio, 2.44; CI, 1.27-4.69).

CONCLUSIONS

Major second dose delays were common, especially for patients given shorter half-life pharmacotherapies and who boarded in the emergency department. They were paradoxically more frequent for patients receiving compliant initial care. We observed association between major second dose delay and increased mortality, length of stay, and mechanical ventilation requirement.

Therapeutic drug monitoring in the past 40 years of the Journal of Antimicrobial Chemotherapy

Since the Journal of Antimicrobial Chemotherapy was first published in 1975, papers addressing therapeutic drug monitoring (TDM) have been a regular feature. Initially they focused on laboratory aspects of drug concentration measurement then they changed more to the application of TDM in a clinical setting. Over its history, the Journal has provided its readership with the latest technological and scientific advances in TDM and has helped to drive changes in TDM that have directly impacted on patient care. These have varied from improvement in the quality of antimicrobial measurements through better identification of dosage regimens and TDM targets that help predict outcome and adverse events. Despite these advances in our understanding of the science and practice of TDM, there remain many areas of uncertainty. As we move into the next 40 years, it is clear that the Journal will continue to provide the readership with the latest science and opinion in this important area.

Strategies to enhance rational use of antibiotics in hospital: a guideline by the German Society for Infectious Diseases

Introduction

In the time of increasing resistance and paucity of new drug development there is a growing need for strategies to enhance rational use of antibiotics in German and Austrian hospitals. An evidence-based guideline on recommendations for implementation of antibiotic stewardship (ABS) programmes was developed by the German Society for Infectious Diseases in association with the following societies, associations and institutions: German Society of Hospital Pharmacists, German Society for Hygiene and Microbiology, Paul Ehrlich Society for Chemotherapy, The Austrian Association of Hospital Pharmacists, Austrian Society for Infectious Diseases and Tropical Medicine, Austrian Society for Antimicrobial Chemotherapy, Robert Koch Institute.

Materials and methods

A structured literature research was performed in the databases EMBASE, BIOSIS, MEDLINE and The Cochrane Library from January 2006 to November 2010 with an update to April 2012 (MEDLINE and The Cochrane Library). The grading of recommendations in relation to their evidence is according to the AWMF Guidance Manual and Rules for Guideline Development.

Conclusion

The guideline provides the grounds for rational use of antibiotics in hospital to counteract antimicrobial resistance and to improve the quality of care of patients with infections by maximising clinical outcomes while minimising toxicity. Requirements for a successful implementation of ABS programmes as well as core and supplemental ABS strategies are outlined. The German version of the guideline was published by the German Association of the Scientific Medical Societies (AWMF) in December 2013.

Optimising Antibiotic Usage to Treat Bacterial Infections

The increase in antibiotic resistant bacteria poses a threat to the continued use of antibiotics to treat bacterial infections. The overuse and misuse of antibiotics has been identified as a significant driver in the emergence of resistance. Finding optimal treatment regimens is therefore critical in ensuring the prolonged effectiveness of these antibiotics. This study uses mathematical modelling to analyse the effect traditional treatment regimens have on the dynamics of a bacterial infection. Using a novel approach, a genetic algorithm, the study then identifies improved treatment regimens. Using a single antibiotic the genetic algorithm identifies regimens which minimise the amount of antibiotic used while maximising bacterial eradication. Although exact treatments are highly dependent on parameter values and initial bacterial load, a significant common trend is identified throughout the results. A treatment regimen consisting of a high initial dose followed by an extended tapering of doses is found to optimise the use of antibiotics. This consistently improves the success of eradicating infections, uses less antibiotic than traditional regimens and reduces the time to eradication. The use of genetic algorithms to optimise treatment regimens enables an extensive search of possible regimens, with previous regimens directing the search into regions of better performance.

[Influence of systemic inflammatory response syndrome on the pharmacokinetics of vancomycin]

Therapeutic drug monitoring (TDM) of vancomycin (VCM) is recommended to minimize its nephrotoxicity and maximize efficacy. Recently, the concept of systemic inflammatory response syndrome (SIRS) has been introduced to describe a clinical state resulting from the actions of complex intrinsic mediators in an acute-phase systemic response. However, there are few reports on the pharmacokinetics of VCM in patients with SIRS. This study investigated the effect of SIRS on the pharmacokinetics of VCM by analyzing the predictability of TDM and pharmacokinetic parameters in 31 non-SIRS patients and 52 SIRS patients, with stratification by SIRS score. The mean prediction error (ME) and mean absolute prediction error in SIRS score 2 and 3 patients differed from those in non-SIRS patients. The ME in the score 4 group showed a negative value. In the comparison of pharmacokinetic parameters by SIRS score, a significantly lower CL(vcm) value was observed at score 4 compared with scores 2 and 3, a higher Vd value was observed at score 4 compared with non-SIRS and at score 3, and a longer T1/2 was observed at score 2. In the comparison of patient characteristics by SIRS score, albumin, aspartate aminotransferase, and alanine aminotransferase levels showed differences among the scores. However, no correlation was observed between VCM pharmacokinetics and these three laboratory parameters. These findings suggest that the pharmacokinetics of VCM may be affected by the pathology of SIRS rather than by patient characteristics.

Right first time!

Septic shock is still a lethal disease in intensive care units (ICU). The mortality can exceed 40% even with therapeutic management. The high mortality is clearly associated with the delay of appropriate antimicrobial therapy. Early diagnosis and identification of infectious source is the mainstay of optimal therapeutic management. On the other hand, source control and optimize antibiotic dosing according to pharmacokinetics (PK)/pharmacodynamics (PD) properties of antibiotics and organ dysfunction of patients are required to get the best clinical outcome.

Change of teicoplanin loading dose requirement for incremental increases of systemic inflammatory response syndrome score in the setting of sepsis

Background Target trough concentrations are recommended for teicoplanin (TEIC) to minimize its adverse effects and to maximize efficacy in sepsis caused by grampositive cocci, including methicillin-resistant Staphylococcus aureus infection. However, optimal doses to attain proper trough values in patients with sepsis have not yet been well established for TEIC. Objective This study investigated whether the systemic inflammatory response syndrome (SIRS) score could predict the pharmacokinetics of TEIC in patients with sepsis. Setting This study was conducted at Fukuoka University Hospital in Japan. Methods We retrospectively reviewed the records of patients using TEIC between April 2012 and March 2015. SIRS positive was defined as infection with a SIRS score ≥2. Estimates of pharmacokinetic parameters were calculated using a Bayesian method. Creatinine clearance rates were estimated by the Cockcroft-Gault formula (eCcr). Main outcome measure Change of TEIC loading dose requirement for incremental increases of SIRS score. Results In total, 133 patients were enrolled: 50 non-SIRS patients and 83 patients with SIRS. The TEIC plasma trough concentration was significantly lower in SIRS than non-SIRS patients (15.7 ± 7.1 vs. 20.1 ± 8.6 μg/mL; P < 0.01), although there was no significant difference in the loading dose administered. Moreover, SIRS scores were increasingly predictive of eCcr and TEIC clearance in a stepwise manner. To achieve the target trough concentration (15-30 μg/mL), the optimal doses required in non-SIRS versus SIRS patients were 12-24 versus 18-30 mg/kg/day, respectively, during the first 48 h. Conclusions These findings suggest that the pharmacokinetics of TEIC are altered in SIRS patients, who required higher doses than non-SIRS patients to achieve the target trough concentration. We suggest that the SIRS score can become a new modality to determine the initial TEIC loading dose.

Frequency of antibiotic application drives rapid evolutionary adaptation of Escherichia coli persistence

The evolution of antibiotic resistance is a major threat to society and has been predicted to lead to 10 million casualties annually by 2050(1). Further aggravating the problem, multidrug tolerance in bacteria not only relies on the build-up of resistance mutations, but also on some cells epigenetically switching to a non-growing antibiotic-tolerant 'persister' state(2-6). Yet, despite its importance, we know little of how persistence evolves in the face of antibiotic treatment(7). Our evolution experiments in Escherichia coli demonstrate that extremely high levels of multidrug tolerance (20-100%) are achieved by single point mutations in one of several genes and readily emerge under conditions approximating clinical, once-daily dosing schemes. In contrast, reversion to low persistence in the absence of antibiotic treatment is relatively slow and only partially effective. Moreover, and in support of previous mathematical models(8-10), we show that bacterial persistence quickly adapts to drug treatment frequency and that the observed rates of switching to the persister state can be understood in the context of 'bet-hedging' theory. We conclude that persistence is a major component of the evolutionary response to antibiotics that urgently needs to be considered in both diagnostic testing and treatment design in the battle against multidrug tolerance.

Doripenem Treatment during Continuous Renal Replacement Therapy

Doripenem is a broad-spectrum parenteral carbapenem with enhanced activity against Pseudomonas aeruginosa. While the initial dosing recommendation for renally competent patients and patients undergoing continuous renal replacement therapy (cRRT) was 500 mg every 8 h (q8h), the dose for renally competent patients was updated to 1 g q8h in June 2012. There are no updated data for the dosing of patients on continuous renal replacement therapy. The original dosing regimen for cRRT patients was based on nonseptic patients, while newer publications chose comparatively low target concentrations for a carbapenem. Thus, there is an urgent need for updated recommendations for dosing during cRRT. In the trial presented here, we included 13 oliguric septic patients undergoing cRRT in an intensive care setting. Five patients each were treated with hemodiafiltration or hemodialysis, while three patients received hemofiltration treatment. All patients received 1 g doripenem every 8 h. Doripenem concentrations in the plasma and ultrafiltrate were measured over 48 h. The mean hemofilter clearance was 36.53 ml/min, and the mean volume of distribution was 59.26 liters. The steady-state trough levels were found at 8.5 mg/liter, with no considerable accumulation. Based on pharmacokinetic and pharmacodynamic considerations, we propose a regimen of 1 g q8h, which may be combined with a loading dose of 1.5 to 2 g for critically ill patients. (This study has been registered with EudraCT under registration no. 2009-018010-18 and at ClinicalTrials.gov under registration no. NCT02018939.).

Colistin as a potentiator of anti-TB drug activity against Mycobacterium tuberculosis

OBJECTIVES

The mycobacterial cell wall is an effective permeability barrier that limits intracellular concentrations of anti-TB drugs and hampers the success of treatment. We hypothesized that colistin might enhance the efficacy of anti-TB drugs by increasing mycobacterial cell wall permeability. In this study, we investigated the additional effect of colistin on the activity of anti-TB drugs against Mycobacterium tuberculosis in vitro.

METHODS

The concentration-dependent and time-dependent killing activity of isoniazid, rifampicin or amikacin alone or in combination with colistin against M. tuberculosis H37Rv was determined. Mycobacterial populations with both high and low metabolic activity were studied, and these were characterized by increasing or steady levels of ATP, respectively.

RESULTS

With exposure to a single drug, striking differences in anti-TB drug activity were observed when the two mycobacterial populations were compared. The addition of colistin to isoniazid and amikacin resulted in sterilization of the mycobacterial load, but only in the M. tuberculosis population with high metabolic activity. The emergence of isoniazid and amikacin resistance was completely prevented by the addition of colistin.

CONCLUSIONS

The results of this study emphasize the importance of investigating mycobacterial populations with both high and low metabolic activity when evaluating the efficacy of anti-TB drugs in vitro. This is the first study showing that colistin potentiates the activity of isoniazid and amikacin against M. tuberculosis and prevents the emergence of resistance to anti-TB drugs. These results form the basis for further studies on the applicability of colistin as a potentiator of anti-TB drugs.

Determination of [11C]rifampin pharmacokinetics within Mycobacterium tuberculosis-infected mice by using dynamic positron emission tomography bioimaging

Information about intralesional pharmacokinetics (PK) and spatial distribution of tuberculosis (TB) drugs is limited and has not been used to optimize dosing recommendations for new or existing drugs. While new techniques can detect drugs and their metabolites within TB granulomas, they are invasive, rely on accurate resection of tissues, and do not capture dynamic drug distribution in the tissues of interest. In this study, we assessed the in situ distribution of (11)C-labeled rifampin in live, Mycobacterium tuberculosis-infected mice that develop necrotic lesions akin to human disease. Dynamic positron emission tomography (PET) imaging was performed over 60 min after injection of [(11)C]rifampin as a microdose, standardized uptake values (SUV) were calculated, and noncompartmental analysis was used to estimate PK parameters in compartments of interest. [(11)C]rifampin was rapidly distributed to all parts of the body and quickly localized to the liver. Areas under the concentration-time curve for the first 60 min (AUC0-60) in infected and uninfected mice were similar for liver, blood, and brain compartments (P > 0.53) and were uniformly low in brain (10 to 20% of blood values). However, lower concentrations were noted in necrotic lung tissues of infected mice than in healthy lungs (P = 0.03). Ex vivo two-dimensional matrix-assisted laser desorption ionization (MALDI) imaging confirmed restricted penetration of rifampin into necrotic lung lesions. Noninvasive bioimaging can be used to assess the distribution of drugs into compartments of interest, with potential applications for TB drug regimen development.

Translating slow-binding inhibition kinetics into cellular and in vivo effects

Many drug candidates fail in clinical trials owing to a lack of efficacy from limited target engagement or an insufficient therapeutic index. Minimizing off-target effects while retaining the desired pharmacodynamic (PD) response can be achieved by reduced exposure for drugs that display kinetic selectivity in which the drug-target complex has a longer half-life than off-target-drug complexes. However, though slow-binding inhibition kinetics are a key feature of many marketed drugs, prospective tools that integrate drug-target residence time into predictions of drug efficacy are lacking, hindering the integration of drug-target kinetics into the drug discovery cascade. Here we describe a mechanistic PD model that includes drug-target kinetic parameters, including the on- and off-rates for the formation and breakdown of the drug-target complex. We demonstrate the utility of this model by using it to predict dose response curves for inhibitors of the LpxC enzyme from Pseudomonas aeruginosa in an animal model of infection.

Antimicrobial dosing in critically ill patients with sepsis-induced acute kidney injury

Severe sepsis often leads to multiple organ dysfunction syndromes (MODS) with acute kidney injury (AKI). AKI affects approximately, 35% of Intensive Care Unit patients, and most of these are due to sepsis. Mortality rate of sepsis-induced AKI is high. Inappropriate use of antimicrobials may be responsible for higher therapeutic failure, mortality rates, costs and toxicity as well as the emergence of resistance. Antimicrobial treatment is particularly difficult due to altered pharmacokinetic profile, dynamic changes in patient's clinical status and, in many cases, need for renal replacement therapy. This article aims to describe the appropriate antimicrobial dosing and reviews the factors contributing to the difficulties in establishing precise guidelines for antimicrobial dosing in sepsis-induced AKI patients.

SEARCH STRATEGY

Text material was collected by systematic search in PubMed, Google (1978-2013) for original articles.

Early management of sepsis

Increased awareness of the signs and symptoms of sepsis and an emphasis on the importance of early treatment have helped to improve survival rates from this serious and frequent condition in recent years. With no specific, effective anti-sepsis therapies available, management focuses on early source control with adequate and appropriate antibiotics and removal of any source of infection, rapid resuscitation, hemodynamic stabilization and organ support. Use of dedicated teams to care for patients with sepsis can help optimize early management.

Quantification of linezolid in serum by LC-MS/MS using semi-automated sample preparation and isotope dilution internal standardization

BACKGROUND

Linezolid serum concentrations have been shown to be highly variable in critically ill patients with often sub-therapeutic drug levels regarding minimal inhibitory concentrations for relevant pathogens. Consequently, therapeutic drug monitoring of linezolid must be considered, requiring a reliable and convenient analytical method. We therefore developed and validated an LC-MS/MS method applying isotope dilution internal standardization and on-line solid phase extraction for serum linezolid quantification.

METHODS

Sample preparation was based on protein precipitation and on-line solid phase extraction with two-dimensional liquid chromatography and column switching. Three-fold deuterated linezolid was used as the internal standard. The method was validated involving two separate LC-MS/MS systems covering the concentration range of 0.13-32 mg/L. The run time was 4 min.

RESULTS

Validation revealed good analytical performance, with inaccuracy <6% and imprecision of <7.3% (CV) for six quality control samples (0.38-16.0 mg/L). The method was found to be robust during the validation process and during a pharmacokinetic study so far involving 600 samples. Comparative measurements on two LC-MS/MS systems revealed close agreement.

CONCLUSIONS

This LC-MS/MS assay described herein is a convenient, robust and reliable method for linezolid quantification in serum which can be routinely applied using different LC-MS/MS systems. The method can be used for clinical studies and subsequent TDM of linezolid.