Use of vancomycin pharmacokinetic-pharmacodynamic properties in the treatment of MRSA infections

Development of an on-site therapeutic drug monitoring method using a portable spectrometer

We report on the development of an on-site therapeutic drug monitoring (TDM) method for vancomycin (VCM) utilizing a portable spectrometer and commercially available immunoturbidimetric assay reagents designed for automated clinical chemistry analyzers. The method enables the quantification of VCM in plasma samples within 10 min, with a good correlation between the measured values and the theoretical values (r2 = 0.995). The intra and inter-day precisions were found to be below 12.5% and 17.7%, respectively. Moreover, we established a correlation between the quantitative values using this method and those measured through HPLC-UV and automated clinical chemistry analyzers, showing good reliability (R2 = 0.970 and 0.951, respectively). This method allows anyone to rapidly perform TDM at the bedside and is expected to be used to evaluate appropriate drug therapy.

Population pharmacokinetics of vancomycin in patients with diabetic foot infection: a comparison of five models

Purpose

This study aimed to compare individual pharmacokinetic (PK) parameters of vancomycin with predicted values from five population PK models in patients with diabetic foot infections (DFIs).

Methods

Patients with a diagnosis of DFI and an estimated glomerular filtration rate (eGFR) ≥ 30 mL/min were included in the study. Individual PK data was carried on by collecting three vancomycin serum concentrations in a steady-state condition. Five published population-based nomograms were assumed to predict PK parameters. Optimal vancomycin exposure was considered as a trough level of 15-20 mg/L or the area under the curve over 24 h/minimum inhibitory concentration (AUC24/MIC) ≥ 400.

Results

A total of 48 samples from 16 patients were analyzed. There was a statistically significant difference between the volume of distribution (Vd) obtained from population methods and the individual estimations (P ≤ 0.001 in Ambrose and Burton, P = 0.010 and 0.006 in Bauer and Burton revised models, respectively). AUC/MIC ≥ 400 was achieved in 68.7% of patients while 50% had a trough level of less than 15 mg/L.

Conclusions

Vancomycin PK parameters, particularly individualized Vd, may not be predictable by population nomograms in patients with DFI and stable renal function. Moreover, the weak correlation between AUC24 values and trough concentrations underlines the starting practice of vancomycin AUC24-based monitoring and dosing in the clinical setting.

Antimicrobial-loaded biodegradable nanoemulsions for efficient clearance of intracellular pathogens in bacterial peritonitis

Intracellular pathogenic bacteria use immune cells as hosts for bacterial replication and reinfection, leading to challenging systemic infections including peritonitis. The spread of multidrug-resistant (MDR) bacteria and the added barrier presented by host cell internalization limit the efficacy of standard antibiotic therapies for treating intracellular infections. We present a non-antibiotic strategy to treat intracellular infections. Antimicrobial phytochemicals were stabilized and delivered by polymer-stabilized biodegradable nanoemulsions (BNEs). BNEs were fabricated using different phytochemicals, with eugenol-loaded BNEs (E-BNEs) affording the best combination of antimicrobial efficacy, macrophage accumulation, and biocompatibility. The positively-charged polymer groups of the E-BNEs bind to the cell surface of macrophages, facilitating the entry of eugenol that then kills the intracellular bacteria without harming the host cells. Confocal imaging and flow cytometry confirmed that this entry occurred mainly via cholesterol-dependent membrane fusion. As eugenol co-localized and interacted with intracellular bacteria, antibacterial efficacy was maintained. E-BNEs reversed the immunosuppressive effects of MRSA on macrophages. Notably, E-BNEs did not elicit resistance selection after multiple exposures of MRSA to sub-therapeutic doses. The E-BNEs were highly effective against a murine model of MRSA-induced peritonitis with better bacterial clearance (99 % bacteria reduction) compared to clinically-employed treatment with vancomycin. Overall, these findings demonstrate the potential of E-BNEs in treating peritonitis and other refractory intracellular infections.

Model-informed precision dosing of vancomycin for rapid achievement of target area under the concentration-time curve: A simulation study

In this study, we aimed to evaluate limited sampling strategies for achieving the therapeutic ranges of the area under the concentration-time curve (AUC) of vancomycin on the first and second day (AUC0-24 , AUC24-48 , respectively) of therapy. A virtual population of 1000 individuals was created using a population pharmacokinetic (PopPK) model, which was validated and incorporated into our model-informed precision dosing tool. The results were evaluated using six additional PopPK models selected based on a study design of prospective or retrospective data collection with sufficient concentrations. Bayesian forecasting was performed to evaluate the probability of achieving the therapeutic range of AUC, defined as a ratio of estimated/reference AUC within 0.8-1.2. The Bayesian posterior probability of achieving the AUC24-48 range increased from 51.3% (a priori probability) to 77.5% after using two-point sampling at the trough and peak on the first day. Sampling on the first day also yielded a higher Bayesian posterior probability (86.1%) of achieving the AUC0-24 range compared to the a priori probability of 60.1%. The Bayesian posterior probability of achieving the AUC at steady-state (AUCSS ) range by sampling on the first or second day decreased with decreased kidney function. We demonstrated that second-day trough and peak sampling provided accurate AUC24-48 , and first-day sampling may assist in rapidly achieving therapeutic AUC24-48 , although the AUCSS should be re-estimated in patients with reduced kidney function owing to its unreliable predictive performance.

Discrepancy between perceptions and acceptance of clinical decision support Systems: implementation of artificial intelligence for vancomycin dosing

BACKGROUND

Artificial intelligence (AI) tools are more effective if accepted by clinicians. We developed an AI-based clinical decision support system (CDSS) to facilitate vancomycin dosing. This qualitative study assesses clinicians' perceptions regarding CDSS implementation.

METHODS

Thirteen semi-structured interviews were conducted with critical care pharmacists, at Mayo Clinic (Rochester, MN), from March through April 2020. Eight clinical cases were discussed with each pharmacist (N = 104). Following initial responses, we revealed the CDSS recommendations to assess participants' reactions and feedback. Interviews were audio-recorded, transcribed, and summarized.

RESULTS

The participants reported considerable time and effort invested daily in individualizing vancomycin therapy for hospitalized patients. Most pharmacists agreed that such a CDSS could favorably affect (N = 8, 62%) or enhance (9, 69%) their ability to make vancomycin dosing decisions. In case-based evaluations, pharmacists' empiric doses differed from the CDSS recommendation in most cases (88/104, 85%). Following revealing the CDSS recommendations, we noted 78% (69/88) discrepant doses. In discrepant cases, pharmacists indicated they would not alter their recommendations. The reasons for declining the CDSS recommendation were general distrust of CDSS, lack of dynamic evaluation and in-depth analysis, inability to integrate all clinical data, and lack of a risk index.

CONCLUSION

While pharmacists acknowledged enthusiasm about the advantages of AI-based models to improve drug dosing, they were reluctant to integrate the tool into clinical practice. Additional research is necessary to determine the optimal approach to implementing CDSS at the point of care acceptable to clinicians and effective at improving patient outcomes.

Plasma and Cerebrospinal Fluid Population Pharmacokinetics of Vancomycin in Patients with External Ventricular Drain

Vancomycin is a commonly used antibacterial agent in patients with primary central nervous system (CNS) infection. This study aims to examine predictors of vancomycin penetration into cerebrospinal fluid (CSF) in patients with external ventricular drainage and the feasibility of CSF sampling from the distal drainage port for therapeutic drug monitoring. Fourteen adult patients (9 with primary CNS infection) were treated with vancomycin intravenously. The vancomycin concentrations in blood and CSF (from proximal [CSF_P] and distal [CSF_D] drainage ports) were evaluated by population pharmacokinetics. Model-based simulations were conducted to compare various infusion modes. A three-compartment model with first-order elimination best described the vancomycin data. Estimated parameters included clearance (CL, 4.53 L/h), central compartment volume (Vc, 24.0 L), apparent CSF compartment volume (VCSF, 0.445 L), and clearance between central and CSF compartments (QCSF, 0.00322 L/h and 0.00135 L/h for patients with and without primary CNS infection, respectively). Creatinine clearance was a significant covariate on vancomycin CL. CSF protein was the primary covariate to explain the variability of QCSF. There was no detectable difference between the data for sampling from the proximal and the distal port. Intermittent infusion and continuous infusion with a loading dose reached the CSF target concentration faster than continuous infusion only. All infusion schedules reached similar CSF trough concentrations. Beyond adjusting doses according to renal function, starting treatment with a loading dose in patients with primary CSF infection is recommended. Occasionally, very high and possibly toxic doses would be required to achieve adequate CSF concentrations, which calls for more investigation of direct intraventricular administration of vancomycin. (This study has been registered at ClinicalTrials.gov under registration no. NCT04426383).

Dose optimization of vancomycin in obese patients: A systematic review

Background: Dose optimization of vancomycin plays a substantial role in drug pharmacokinetics because of the increased incidence of obesity worldwide. This systematic review was aimed to highlight the current dosing strategy of vancomycin among obese patients. Methods: This systematic review was in concordance with Preferred Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The literature search was carried out on various databases such as Scopus, PubMed/MEDLINE, ScienceDirect and EMBASE using Keywords and MeSH terms related to vancomycin dosing among obese patients. Google Scholar was also searched for additional articles. The English language articles published after January, 2000 were included in this study. The quality of the study was assessed using different assessment tools for cohort, and case reports. Results: A total of 1,029 records were identified. After screening, 18 studies were included for the final review. Of total, twelve studies are retrospective and remaining six are case-control studies. A total of eight studies were conducted in pediatrics while remaining studies were conducted in adult population. Most of the studies reported the dosing interval every 6-8 h. Differences in target trough concentration exist with respect to target ranges. The administration of loading dose (20-25 mg/kg) followed by maintenance dose (15-25 mg/kg) of vancomycin is recommended in adult patients to target therapeutic outcomes. Moreover, a dose of 40-60 mg/kg/day appears appropriate for pediatric patients. Conclusion: The initial dosing of vancomycin based on TBW could be better predictor of vancomycin trough concentration. However, the clinical significance is uncertain. Therefore, more studies are needed to evaluate the dosing strategy of vancomycin in overweight or obese patients.

Norvancomycin for the Treatment of Central Nervous System MRSA Infections: a Randomized Controlled Trial: Norvancomycin for the Treatment of Central nervous system MRSA infections

Combined intravenous and intrathecal administration of norvancomycin (NVCM) is routinely employed in treating methicillin-resistant Staphylococcus aureus (MRSA) ventriculitis in patients following craniotomy. However, the optimal dosing regimen, the pharmacokinetics (PK) of NVCM in cerebrospinal fluid (CSF), and the clinical outcome are yet to be elucidated. Herein, a single-center randomized controlled trial was conducted in the Neurosurgery Department of the Second Hospital of Hebei Medical University (Shijiazhuang, China). Patients with MRSA ventriculitis after craniotomy were randomly assigned to two groups. The control group received 800 mg NVCM intravenously every 12 h, and the experimental group received 800 mg NVCM intravenously every 12 h and 16 mg NVCM intrathecal administration every 24 h. The primary outcome was the length of therapy, while the secondary outcomes included the area under the concentration-time curve in 0-24 h/minimum inhibitory concentration ratio (AUC_0-24h/MIC) of NVCM in CSF. A total of 29 patients (14 in the experimental group and 15 in the control group) were included in this study. Of these, 24 constituted the final analysis population, with 12 in each group. The average length of therapy in the experimental group was markedly shorter than that of the control group (11.2 ± 2.6 days vs. 16.6 ± 5.2 days, P = 0.005), while the AUC_0-24h/MIC in the experimental group was significantly higher than that in the control group (2306.57 ± 928.58 vs. 46.83 ± 27.48, P <0.001) with no increase in adverse reactions. Combined intravenous and intrathecal administration can shorten the treatment time of intracranial infection without higher adverse reaction risks in our research. Further studies with larger sample size are warranted to verify its safety and efficacy.

A study to explore the appropriateness of dosing regimen of vancomycin in critically ill patients in a tertiary care unit of India

Introduction

Vancomycin is used in proven or suspected MRSA and MRE infections. An AUC/MIC ratio of ≥400 is the current accepted critical PK/PD"efficacy" target of vancomycin activity. The present study was conducted to ascertain the appropriateness of practice of current dosage regimen of vancomycin (1 g BD) based on population pharmacokinetic approach.

Methods

A single-center prospective study with the ICU setting of a tertiary care center was conducted. A total of 15 adult patients with sepsis treated with vancomycin were included over 15 months from May 2019 to July 2020. Blood samples were obtained at 5, 10, and 30 minutes and thereafter at 2 and 6 hours following the completion of the vancomycin infusion. The data obtained from HPLC estimation was analyzed using a population pharmacokinetic approach with NLME, Phoenix 8.3.2.166. The pharmacokinetic model was based on covariates such as bodyweight and urinary creatinine clearance to predict drug concentrations.

Results

A total of 83 vancomycin blood samples were analyzed. The mean AUC_0-last and AUC_0-∞ in patients who improved and died were (AUC_(0-last)=293 (152.97); AUC_(0-∞)=535.14 (353.67) and (AUC_(0-last)=137.19 (51.37); AUC_(0-∞)=582.12 (1036.09) respectively, the difference between the two outcome groups was not statistically significant (p=0.104). The pharmacokinetic model was best described by a two-compartment linear model. The goodness-of-fit plots showed that the final covariate pharmacokinetic model (having bodyweight and urinary creatinine clearance) adequately described the observed vancomycin concentrations.

Conclusions

Based on the finding of the study it was concluded that 1 g BD dosing of vancomycin is inappropriate. Including covariates such as urinary creatinine clearance and weight in the pharmacokinetic model helped predict drug concentrations more accurately. However, further studies are required to demonstrate efficacy regarding applying this strategy.

Clinical Practice Guidelines for Therapeutic Drug Monitoring of Vancomycin in the Framework of Model-Informed Precision Dosing: A Consensus Review by the Japanese Society of Chemotherapy and the Japanese Society of Therapeutic Drug Monitoring

Background: To promote model-informed precision dosing (MIPD) for vancomycin (VCM), we developed statements for therapeutic drug monitoring (TDM). Methods: Ten clinical questions were selected. The committee conducted a systematic review and meta-analysis as well as clinical studies to establish recommendations for area under the concentration-time curve (AUC)-guided dosing. Results: AUC-guided dosing tended to more strongly decrease the risk of acute kidney injury (AKI) than trough-guided dosing, and a lower risk of treatment failure was demonstrated for higher AUC/minimum inhibitory concentration (MIC) ratios (cut-off of 400). Higher AUCs (cut-off of 600 μg·h/mL) significantly increased the risk of AKI. Although Bayesian estimation with two-point measurement was recommended, the trough concentration alone may be used in patients with mild infections in whom VCM was administered with q12h. To increase the concentration on days 1–2, the routine use of a loading dose is required. TDM on day 2 before steady state is reached should be considered to optimize the dose in patients with serious infections and a high risk of AKI. Conclusions: These VCM TDM guidelines provide recommendations based on MIPD to increase treatment response while preventing adverse effects.

Environmental conditions dictate differential evolution of vancomycin resistance in Staphylococcus aureus

While microbiological resistance to vancomycin in Staphylococcus aureus is rare, clinical vancomycin treatment failures are common, and methicillin-resistant S. aureus (MRSA) strains isolated from patients after prolonged vancomycin treatment failure remain susceptible. Adaptive laboratory evolution was utilized to uncover mutational mechanisms associated with MRSA vancomycin resistance in a physiological medium as well as a bacteriological medium used in clinical susceptibility testing. Sequencing of resistant clones revealed shared and media-specific mutational outcomes, with an overlap in cell wall regulons (walKRyycHI, vraSRT). Evolved strains displayed similar properties to resistant clinical isolates in their genetic and phenotypic traits. Importantly, resistant phenotypes that developed in physiological media did not translate into resistance in bacteriological media. Further, a bacteriological media-specific mechanism for vancomycin resistance associated with a mutated mprF was confirmed. This study bridges the gap between the understanding of clinical and microbiological vancomycin resistance in S. aureus and expands the number of allelic variants (18 ± 4 mutations for the top 5 mutated genes) that result in vancomycin resistance phenotypes.

Transdermal delivery of vancomycin hydrochloride: Influence of chemical and physical permeation enhancers

Topical and transdermal delivery of vancomycin hydrochloride (VH), a broad-spectrum peptide antibiotic, is a challenge because of its high molecular weight (1485.7 Da) and hydrophilicity (log P -3.1). The objective of this study was to investigate the feasibility of delivering VH into and across the skin using permeation enhancement techniques. Skin permeation studies were performed using Franz diffusion cell apparatus in the excised porcine skin model. The influence of co-treatment and pre-treatment of chemical permeation enhancers (oleic acid and palmitic acid) on permeation of VH across intact and tape-stripped skin was evaluated. In addition, continuous anodal iontophoresis was applied to enhance the skin permeation of VH. The mechanism of skin permeation enhancement by palmitic acid was investigated using FTIR spectroscopy, impedance spectroscopy, and thermal analysis techniques. Pharmacokinetic analysis was performed after the topical application of VH formulations in Sprague Dawley rats. Results from permeation studies showed that VH did not passively permeate across the intact skin after 48 h, whereas the cumulative amount of VH permeated across the tape-stripped skin was found to be 854 ± 67 µg/cm². A combination of tape-stripping and chemical enhancers resulted in enhancing the cumulative amount of VH permeated across the skin by 2- and 10-fold with oleic acid and palmitic acid application, respectively. Similarly, 2 and 12 h pre-treatment of tape-stripped skin with palmitic acid enhanced the flux of VH across the skin by 1.7- and 5-fold, respectively. It was found that tape-stripping and the palmitic acid application would provide greater VH permeation compared with 0.31 mA/cm² iontophoresis application. Thermal analysis and impedance spectroscopic analysis showed that palmitic acid interacts with epidermal lipids to enhance VH permeation. Pharmacokinetic analysis after topical application showed that the C_max and mean residence time increased by 3-fold with the application of VH and palmitic acid on tape-stripped skin compared with free VH on intact skin. Taken together, VH can be delivered through the topical route using a combination of chemical enhancer and tape-stripping to treat local and systemic bacterial infections.

Transitioning From Consult-Based to Automatic Pharmacy-Driven Vancomycin Management: Results From a Single, Primary Care Center

OBJECTIVE

The transition to area under the curve (AUC) vancomycin monitoring requires substantial updates in pharmacy policies and procedures. The study facility was tasked with transitioning from a consult-based collaborative agreement to an automatic pharmacist management policy on all intravenous (IV) vancomycin orders. The purpose of this quality assessment (QA) study was to evaluate the effectiveness of this transition.

METHODS

The primary outcome was the proportion of patients with pharmacist assessment of pharmacokinetics and dosing with documentation in IV vancomycin treated patients from January-June 2020. Secondary outcomes included the proportion of AUC₂₄ levels within therapeutic range, the incidence of acute kidney injury (AKI) and treatment failures in patients treated ≥72 hours compared to a historical, trough-based cohort.

RESULTS

There were 88 patients in the QA analysis with 100% having a pharmacist assessment with documentation. There were 34 patients treated ≥72 hours in the AUC group, 36 in the trough-based group. AUC₂₄ fell within desired range in 45% of monitored patients. Rates of AKI (9% vs 11%, p = 0.75) and treatment failures were similar (3% vs 0%, p = 0.3).

CONCLUSION

The transition from consult-based to an automatic pharmacy management agreement was successful with similar safety and efficacy compared to a historical trough-based cohort.

Population Pharmacokinetics of Vancomycin in Kidney Transplant Recipients: Model Building and Parameter Optimization

Background

Depending on the renal function of patients and many other influencing factors, studies on vancomycin pharmacokinetics show significant inter- and intra-individual variability. The present study was conducted using a population pharmacokinetics method to investigate the pharmacokinetic parameters and identified their influencing covariates for intravenous vancomycin in adult kidney transplant recipients.

Methods

The drug monitoring data included 56 adult renal transplant recipients who received intravenous vancomycin as prophylactic medication. The analysis was performed by a population approach with NONMEM. Data were collected mainly during the first week after transplantation. Monitoring of vancomycin trough concentration in blood was initiated mainly 3–5 days after the initial administration.

Results

The one-compartment open model was optimal and adequately described the data. Body weight (WT) and estimated glomerular filtration rate (GFR) were identified as significant covariates of the pharmacokinetic parameters CL and V of intravenous vancomycin in the kidney transplant patients. The typical values of vancomycin CL and V were 2.08 L h^-1 and 63.2 L, respectively. A dosage strategy scheme according to model results was also designed.

Conclusion

Both WT and GFR of the kidney transplant patients positively influence the pharmacokinetic parameters CL and V for intravenous vancomycin. Our population pharmacokinetic model provides a reference for vancomycin dosage adjustment in kidney transplant recipients.

Susceptibility of clinical isolates of meticillin-resistant Staphylococcus aureus and phenotypic non-extended-spectrum β-lactamase-producing Klebsiella pneumoniae to ceftaroline in Taiwan: Results from Antimicrobial Testing Leadership and Surveillance (ATLAS) in 2012-2018 and Surveillance of Multicentre Antimicrobial Resistance in Taiwan (SMART) in 2018-2019

Data on ceftaroline (CPT) susceptibility amongst clinical isolates of meticillin-resistant Staphylococcus aureus (MRSA, n=1284) and phenotypic non-extended-spectrum β-lactamase-producing (non-ESBL-P) Klebsiella pneumoniae (n=466), obtained from the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme from 2012 to 2018, and selected MRSA isolates from patients with bloodstream infections (BSIs) (n=95) from the Surveillance of Multicentre Antimicrobial Resistance in Taiwan (SMART) programme from 2018 to 2019 were analysed. The minimum inhibitory concentrations (MICs) of ATLAS isolates were determined using the broth microdilution method, whereas the MICs of SMART BSI-MRSA isolates were determined using the Etest and MicroScan system. The pharmacokinetic profiles and pharmacodynamic parameters of CPT were applied to explore the optimal dosage against infections caused by Taiwanese MRSA and K. pneumoniae isolates. Approximately 7.1% of ATLAS MRSA isolates were susceptible-dose dependent (S-DD) to CPT, and 19.7% of the non-ESBL-P K. pneumoniae isolates were not susceptible to CPT. Amongst the ATLAS MRSA isolates, the S-DD rates to CPT amongst isolates causing lower respiratory tract infections were 11.9% and 8.5% for isolates from intensive care units (ICUs) and general wards (GWs), and those causing skin and soft tissue infections (SSTIs) were 20% and 5.3% for isolates from ICUs and GWs, respectively (P=0.015). Of the SSTI MRSA isolates from GWs, 22.7% displayed vancomycin MICs >1 mg/L. Amongst 95 SMART BSI MRSA isolates, 28 (46.7%) isolates exhibited lower CPT MICs by the Etest compared with 60 isolates with CPT MICs of 1-2 mg/L by the MicroScan system. CPT 600 mg as a 2-h intravenous infusion every 8 h is suggested for treatment of infections caused by MRSA and phenotypic non-ESBL-P K. pneumoniae in Taiwan.

Weight-based vancomycin loading strategy may not improve achievement of optimal vancomycin concentration in patients with preserved renal function

We performed a retrospective study to evaluate clinical effectiveness of vancomycin loading strategy and factors associated with achieving optimal C _min. Patients administered vancomycin for ≥72 h from January to June 2018 were enrolled. Patients were divided into two groups: loading (LD) and non-loading (NLD). LD was defined as initial vancomycin dose ≥20 mg/kg and ≥120% of maintenance dose. During study period, 70 and 71 received initial LD (24.2 ± 2.5 mg/kg) and NLD (17.3 ± 3.3 mg/kg) doses of vancomycin, respectively (p < .001). Achievement of optimal C _min was not different before administration of the third dose (24.4% in LD versus 18.2% in NLD, p = .484) and within 72 h (22.9% versus 28.2%, p = .759). Risk factors for failure to achieve optimal C _min before administration of the third dose were higher creatinine clearance and higher level of serum albumin. Therefore, more sufficient loading or patient-specific dose strategies should be used to achieve optimal serum vancomycin C _min.

High sensitivity versus low level of vancomycin needs to be concern for another alternative anti- Staphylococcus aureus as the first- line antibiotic

Background and aim: Vancomycin has been the first-line therapy for MRSA infection disease for many years. According to standard guidelines, the therapeutic vancomycin trough concentration should be above 10 mg/L and optimally between 15-20 mg/L. The aim of this study was to evaluate vancomycin trough level concentration in patients infected with MRSA.Methods: This cross- sectional study included a sample of 170 patients admitted to the ICU of Loghman hospital. We used a standard questionnaire, then applied appropriate statistical tests. All collected data had been analyzed and interpreted by IBM SPSS Statistics 19.0.Results: Among this study population, 71.8% was male. Just 20.8% of the patients can reach the therapeutic level trough even after changing the dose. It should be noted that a significant percentage of toxicity was observed after increasing the dose. Conclusions: Even though high sensitivity against vancomycin disc has been seen in antibiogram tests, sufficient efficiency has not been distinguished, in the sense that, just a few patients by low trough level concentration, reached to therapeutic level after the dose change. Based on some sources, because of the side effects and limited safe range of vancomycin, we should consider a new approach to the alternative antibiotics. (www.actabiomedica.it)

Model-based Evaluation of the Clinical and Microbiological Efficacy of Vancomycin: A Prospective Study of Chinese Adult In-house Patients

Background

Our aims in this prospective study were to evaluate the correlations between pharmacokinetic/pharmacodynamic (PK/PD) indices and the clinical/microbiological efficacy of vancomycin and to identify an appropriate PK/PD target in the Chinese population to guide vancomycin treatment in the clinic.

Methods

Adult patients from 11 hospitals in China with gram-positive infections who received vancomycin therapy for ≥5 days and who were under therapeutic drug monitoring (TDM) were enrolled in this study. A 1-compartment population PK model was established and validated. The correlations between PK/PD indices (Cmin, Cmax, 0-24 hour area under the curve (AUC0-24), and AUC0-24/minimum inhibitory concentration (MIC) and clinical outcomes (clinical efficacy and bacterial eradication) were evaluated.

Results

In total, 402 adult Chinese patients were enrolled. Among them, 380 patients were evaluable for PK analysis, and 334 were evaluable for PK/PD analysis. In the final population PK model, creatinine clearance (CLCR) was the significant covariate on CL (typical value, 3.87 L/hour; between-subject variability (BSV), 12.5%), and age was the significant covariate on volume of distribution (V) (typical value, 45.1 L; BSV, 24.8%). The univariate analysis showed that Cmax, AUC0-24, and AUC0-24/MIC were significantly different or marginally significantly different (P values were 0.009, 0.0385, and 0.0509, respectively) between microbiological outcome groups with coagulase-negative Staphylococcus infections. However, there were no significant differences (P > .05) in the above PK parameters by multivariate logistic regression analysis, indicating there was no independently associated factor.

Conclusions

No significant correlations were identified between PK/PD indices and the clinical or microbiological efficacy of vancomycin in Chinese patients. The necessity of vancomycin TDM based on trough concentration and the current treatment target of AUC0-24/MIC ≥400 need to be further evaluated and confirmed in additional prospective studies.

Interventions targeting the prescribing and monitoring of vancomycin for hospitalized patients: a systematic review with meta-analysis

Purpose

Vancomycin prescribing requires individualized dosing and monitoring to ensure efficacy, limit toxicity, and minimize resistance. Although there are nationally endorsed guidelines from several countries addressing the complexities of vancomycin dosing and monitoring, there is limited consideration of how to implement these recommendations effectively.

Methods

We conducted a systematic search of multiple databases to identify relevant comparative studies describing the impact of interventions of educational meetings, implementation of guidelines, and dissemination of educational material on vancomycin dosing, monitoring, and nephrotoxicity. Effect size was assessed using ORs and pooled data analyzed using forest plots to provide overall effect measures.

Results

Six studies were included. All studies included educational meetings. Two studies used implementation of guidance, educational meetings, and dissemination of educational materials, one used guidance and educational meetings, one educational meetings and dissemination of educational materials, and two used educational meetings solely. Effect sizes for individual studies were more likely to be significant for multifaceted interventions. In meta-analysis, the overall effect of interventions on outcome measures of vancomycin dosing was OR 2.50 (95% CI 1.29–4.84); P< 0.01. A higher proportion of sampling at steady-state concentration was seen following intervention (OR 1.95, 95% CI 1.26–3.02; P<0.01). Interventions had no effect on appropriate timing of trough sample (OR 2.02, 95% CI 0.72–5.72; P=0.18), attaining target concentration in patients (OR 1.50, 95% CI 0.49–4.63; P=0.48, or nephrotoxicity (OR 0.75, 95% CI 0.42–1.34; P=0.33).

Conclusion

Multifaceted interventions are effective overall in improving the complex task of dosing vancomycin, as well as some vancomycin-monitoring outcome measures. However, the resulting impact of these interventions on efficacy and toxicity requires further investigation. These findings may be helpful to those charged with designing implementation strategies for vancomycin guidelines or complex prescribing processes in hospitals.

Appropriateness of vancomycin therapeutic drug monitoring and its outcomes among non-dialysis patients in a tertiary hospital in Singapore

Background Vancomycin therapeutic drug monitoring (TDM) is commonly performed to ensure safe and effective use of the antibiotic. Aim of Study To evaluate appropriateness of vancomycin TDM and its outcomes in Singapore General Hospital. Method A retrospective, cross-sectional study was conducted between 1 January 2014 and 28 February 2014 involving patients who received ≥ 1 dose of intravenous vancomycin with TDM. Patient demographics and relevant vancomycin TDM data were collected from medical records. Results Of 746 vancomycin troughs measured among 234 patients, 459 troughs (61.5%) were taken inappropriately, with a median time of 2.6 h (interquartile range 1.1-4.3) before the next scheduled dose. Inappropriate interpretation of vancomycin troughs resulted in 41 unnecessary dose suspensions, 24 dose changes, and 102 unchanged vancomycin doses. The cost incurred due to inappropriate interpretation and measurement after discontinuation of treatment was US$7286. No differences in rates of vancomycin related nephrotoxicity, ototoxicity, recurrent infection, development of infection secondary to vancomycin resistant microorganism and mortality were observed (p > 0.05). Conclusion This study highlighted a high incidence of inappropriate vancomycin TDM which has led to increased healthcare cost.

Interventions Targeting the Prescribing and Monitoring of Vancomycin for Hospitalized Patients: A Systematic Review Protocol

INTRODUCTION

Vancomycin remains one of our essential antibiotics after fifty years of treating serious infections such as methicillin-resistant Staphylococcus aureus. Vancomycin, unlike many other antibiotic agents, requires individualized dosing and monitoring of serum drug levels to ensure it is efficacious, to minimize toxicity, and to limit the development of antibiotic resistance. These issues have led to numerous vancomycin clinical practice guidelines being published in recent years including several key national guidelines. Significant resources are invested during the development of such guidelines; however, there is often little or no information about how such guidelines or other vancomycin practice improvement initiatives should be implemented. The aim of this systematic review is to identify and evaluate the effect of interventions using education, guideline implementation, and dissemination of educational resources that have sought to improve therapeutic drug monitoring and dosing of vancomycin.

METHODS

A systematic review of the literature will be conducted for RCTs and observational studies where a vancomycin guideline or practice improvement initiative has been implemented. Electronic databases to be searched are PubMed, Medline, CINAHL, EMBASE and the Cochrane Library of Systematic Reviews. The population will be patients who have had intravenous vancomycin prescribed and monitored in hospital. The interventions will be education, implementation of guidelines or protocols, dissemination of educational materials (printed or electronic) or multifaceted interventions of the above. The comparator will be patients who have had standard-care prescribing and monitoring of vancomycin. Outcomes will be changes in prescribing and ordering of vancomycin serum tests, and serum levels attained in patients as well as reported nephrotoxicity. Two reviewers will be involved in the quality assessment and extraction of data. The Scottish Intercollegiate Guidelines Network checklist for RCTs will be used. Studies that are not randomized will be assessed for quality using the validated ROBINS-I (risk of bias in non-randomized studies of interventions) tool.

DISCUSSION

This systematic review will identify interventions that have been used to implement guidelines and clinical practice initiatives for vancomycin. The findings of this review may be informative to those involved with the implementation of vancomycin clinical practice guidelines. Systematic review registration: PROSPERO: CRD42016049147.

Sustained improvement in vancomycin dosing and monitoring post-implementation of guidelines: Results of a three-year follow-up after a multifaceted intervention in an Australian teaching hospital

INTRODUCTION

Despite vancomycin being in use for over half-a-century, it is still not dosed or monitored appropriately in many centers around the world. The objective of this study was to determine the effectiveness of a multifaceted intervention to implement a vancomycin dosing and monitoring guideline across multiple medical and surgical units over time.

METHODS

This was an observational before-and-after interventional cohort study. The pre-intervention period was August to December 2010-2011 and the post-intervention period was September to November 2012-2014. The implementation strategy comprised: face-to-face education, online continuing medical education, dissemination of pocket guideline and email reminder. Outcome measures included: appropriate prescribing of loading and maintenance doses, therapeutic drug monitoring, time to attain target range and nephrotoxicity.

RESULTS

Post-implementation prescribing of loading doses increased (10.4%-43.6%, P=<0.001), guideline adherent first maintenance dose (44%-68.4% P = 0.04), correct dose adjustment from (53.1%-72.2%, P = 0.009). Beneficial effects pre and post-implementation were observed for adherent timing of initial concentration (43.2%-51.9%, P = 0.01), concentrations in target range (32.6%-44.1%, P = 0.001), time to target range (median 6-4 days, P=<0.001), potentially nephrotoxic concentrations (30.7%-20.9%, P=<0.001) and nephrotoxicity (10.4%-6.8%, P=<0.001).

CONCLUSIONS

A multifaceted intervention to implement a vancomycin dosing and monitoring guideline significantly improved prescribing, monitoring, pharmacokinetic and safety outcomes for patients treated with vancomycin over an extended period. However, increased guideline adoption by clinicians is required to maximize and prolong the utility of this important agent.

Dosing strategies to optimize currently available anti-MRSA treatment options (Part 1: IV options)

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) continues to be a predominant pathogen resulting in significant morbidity and mortality. Optimal dosing of anti-MRSA agents is needed to help prevent the development of antimicrobial resistance and to increase the likelihood of a favorable clinical outcome. Areas covered: This review summarizes the available data for antimicrobials routinely used for MRSA infections that are not administered orally or topically. We make recommendations and highlight the current gaps in the literature. A PubMed (1966 - Present) search was performed to identify relevant literature for this review. Expert commentary: Improvements in MIC determination and therapeutic drug monitoring are needed to fully implement individualized dosing that optimizes antimicrobial pharmacodynamics.Additional data will become available for these agents in regards to effectiveness for severe MRSA infections and pharmacokinetic data for special patient populations.

Review on Usage of Vancomycin in Livestock and Humans: Maintaining Its Efficacy, Prevention of Resistance and Alternative Therapy

Vancomycin is one of the “last-line” classes of antibiotics used in the treatment of life-threatening infections caused by Gram-positive bacteria. Even though vancomycin was discovered in the 1950s, it was widely used after the 1980s for the treatment of infections caused by methicillin-resistant Staphylococci, as the prevalence of these strains were increased. However, it is currently evident that vancomycin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci have developed for various reasons, including the use of avaparcin—an analog of vancomycin—as a feed additive in livestock. Therefore, prophylactic and empiric use of antibiotics and their analogues need to be minimized. Herein we discuss the rational use of vancomycin in treating humans, horses, farm animals, and pet animals such as dogs, cats, and rabbits. In present day context, more attention should be paid to the prevention of the emergence of resistance to antibiotics in order to maintain their efficacy. In order to prevent emergence of resistance, proper guidance for the responsible use of antimicrobials is indispensable. Therefore, almost all stakeholders who use antibiotics should have an in-depth understanding of the antibiotic that they use. As such, it is imperative to be aware of the important aspects of vancomycin. In the present review, efforts have been made to discuss the pharmacokinetics and pharmacodynamics, indications, emergence of resistance, control of resistance, adverse effects, and alternative therapy for vancomycin.

[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.

New Regimen for Continuous Infusion of Vancomycin in Critically Ill Patients

Despite the development of new agents with activity against Gram-positive bacteria, vancomycin remains one of the primary antibiotics for critically ill septic patients. Because sepsis can alter antimicrobial pharmacokinetics, the development of an appropriate dosing strategy to provide adequate concentrations is crucial. The aim of this study was to prospectively validate a new dosing regimen of vancomycin given by continuous infusion (CI) to septic patients. We included all adult septic patients admitted to a mixed intensive care unit (ICU) between January 2012 and May 2013, who were treated with a new vancomycin CI regimen consisting of a loading dose of 35 mg/kg of body weight given as a 4-h infusion, followed by a daily CI dose adapted to creatinine clearance (CrCL), as estimated by the Cockcroft-Gault formula (median dose, 2,112 [1,500 to 2,838] mg). Vancomycin concentrations were measured at the end of the loading dose (T1), at 12 h (T2), at 24 h (T3), and the day after the start of therapy (T4). Vancomycin concentrations of 20 to 30 mg/liter at T2, T3, and T4 were considered adequate. A total of 107 patients (72% male) were included. Median age, weight, and CrCL were 59 (interquartile range [IQR], 48 to 71) years, 75 (IQR, 65 to 85) kg, and 94 (IQR, 56 to 140) ml/min, respectively. Vancomycin concentrations were 44 (IQR, 37 to 49), 25 (IQR, 21 to 32), 22 (IQR, 19 to 28), and 26 (IQR, 22 to 29) mg/liter at T1, T2, T3, and T4, respectively. Concentrations were adequate in 56% (60/107) of patients at T2, in 54% (57/105) at T3, and in 73% (41/56) at T4. This vancomycin regimen permitted rapid attainment of target concentrations in serum for most patients. Concentrations were insufficient in only 16% of patients at 12 h of treatment.

Association between the AUC0-24/MIC Ratio of Vancomycin and Its Clinical Effectiveness: A Systematic Review and Meta-Analysis

BACKGROUND

A target AUC0-24/MIC ratio of 400 has been associated with its clinical success when treating Staphylococcus aureus infections but is not currently supported by state-of-the-art evidence-based research.

OBJECTIVE

This current systematic review aimed to evaluate the available evidence for the association between the AUC0-24/MIC ratio of vancomycin and its clinical effectiveness on hospitalized patients and to confirm the existing target value of 400.

METHODS

PubMed, Embase, Web of Sciences, the Cochrane Library and two Chinese literature databases (CNKI, CBM) were systematically searched. Manual searching was also applied. Both RCTs and observational studies comparing the clinical outcomes of high AUC0-24/MIC groups versus low AUC0-24/MIC groups were eligible. Two reviewers independently extracted the data. The primary outcomes were mortality and infection treatment failure. Risk ratios (RRs) with 95% confidence intervals (95%CIs) were calculated.

RESULTS

No RCTs were retrieved. Nine cohort studies were included in the meta-analysis. Mortality rates were significantly lower in high AUC0-24/MIC groups (RR = 0.47, 95%CI = 0.31-0.70, p<0.001). The rates of infection treatment failure were also significantly lower in high AUC/MIC groups and were consistent after correcting for heterogeneity (RR = 0.39, 95%CI = 0.28-0.55, p = 0.001). Subgroup analyses showed that results were consistent whether MIC values were determined by broth microdilution (BMD) method or Etest method. In studies using the BMD method, breakpoints of AUC0-24/MIC all fell within 85% to 115% of 400.

CONCLUSIONS

This meta-analysis demonstrated that achieving a high AUC0-24/MIC of vancomycin could significantly decrease mortality rates by 53% and rates of infection treatment failure by 61%, with 400 being a reasonable target.

Association between the AUC0-24/MIC Ratio of Vancomycin and Its Clinical Effectiveness: A Systematic Review and Meta-Analysis

Background

A target AUC_0-24/MIC ratio of 400 has been associated with its clinical success when treating Staphylococcus aureus infections but is not currently supported by state-of-the-art evidence-based research.

Objective

This current systematic review aimed to evaluate the available evidence for the association between the AUC_0-24/MIC ratio of vancomycin and its clinical effectiveness on hospitalized patients and to confirm the existing target value of 400.

Methods

PubMed, Embase, Web of Sciences, the Cochrane Library and two Chinese literature databases (CNKI, CBM) were systematically searched. Manual searching was also applied. Both RCTs and observational studies comparing the clinical outcomes of high AUC_0-24/MIC groups versus low AUC_0-24/MIC groups were eligible. Two reviewers independently extracted the data. The primary outcomes were mortality and infection treatment failure. Risk ratios (RRs) with 95% confidence intervals (95%CIs) were calculated.

Results

No RCTs were retrieved. Nine cohort studies were included in the meta-analysis. Mortality rates were significantly lower in high AUC_0-24/MIC groups (RR = 0.47, 95%CI = 0.31–0.70, p<0.001). The rates of infection treatment failure were also significantly lower in high AUC/MIC groups and were consistent after correcting for heterogeneity (RR = 0.39, 95%CI = 0.28–0.55, p = 0.001). Subgroup analyses showed that results were consistent whether MIC values were determined by broth microdilution (BMD) method or Etest method. In studies using the BMD method, breakpoints of AUC_0-24/MIC all fell within 85% to 115% of 400.

Conclusions

This meta-analysis demonstrated that achieving a high AUC_0-24/MIC of vancomycin could significantly decrease mortality rates by 53% and rates of infection treatment failure by 61%, with 400 being a reasonable target.

Pharmacist-led implementation of a vancomycin guideline across medical and surgical units: impact on clinical behavior and therapeutic drug monitoring outcomes

Background

Vancomycin is the antibiotic of choice for the treatment of serious infections such as methicillin-resistant Staphylococcus aureus (MRSA). Inappropriate prescribing of vancomycin can lead to therapeutic failure, antibiotic resistance, and drug toxicity.

Objective

To examine the effectiveness of pharmacist-led implementation of a clinical practice guideline for vancomycin dosing and monitoring in a teaching hospital.

Methods

An observational pre–post study design was undertaken to evaluate the implementation of the vancomycin guideline. The implementation strategy principally involved education, clinical vignettes, and provision of pocket guidelines to accompany release of the guideline to the hospital Intranet. The target cohort for clinical behavioral change was junior medical officers, as they perform the majority of prescribing and monitoring of vancomycin in hospitals. Assessment measures were recorded for vancomycin prescribing, therapeutic drug monitoring, and patient outcomes.

Results

Ninety-nine patients, 53 pre- and 46 post-implementation, were included in the study. Prescribing of a loading dose increased from 9% to 28% (P=0.02), and guideline adherence to starting maintenance dosing increased from 53% to 63% (P=0.32). Dose adjustment by doctors when blood concentrations were outside target increased from 53% to 71% (P=0.12), and correct timing of initial concentration measurement increased from 43% to 57% (P=0.23). Appropriately timed trough concentrations improved from 73% to 81% (P=0.08). Pre-dose (trough) concentrations in target range rose from 33% to 44% (P=0.10), while potentially toxic concentrations decreased from 32% to 21% (P=0.05) post-implementation. Infection cure rates for patients increased from 85% to 96% (P=0.11) after the guideline was implemented.

Conclusion

The implementation strategy employed in this study demonstrated potential effectiveness, and should prompt additional larger studies to optimize strategies that will translate into improved clinical practice using vancomycin.

Vancomycin pharmacokinetic models: informing the clinical management of drug-resistant bacterial infections

This review aims to critically evaluate the pharmacokinetic literature describing the use of vancomycin in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. Guidelines recommend that trough concentrations be used to guide vancomycin dosing for the treatment of MRSA infections; however, numerous in vitro, animal model and clinical studies have demonstrated that the therapeutic effectiveness of vancomycin is best described by the area under the concentration versus time curve (AUC) divided by the minimum inhibitory concentration (MIC) of the infecting organism (AUC/MIC). Among patients with lower respiratory tract infections, an AUC/MIC ≥400 was associated with a superior clinical and bacteriological response. Similarly, patients with MRSA bacteremia who achieved an Etest AUC/MIC ≥320 within 48 h were 50% less likely to experience treatment failure. For other patient populations and different clinical syndromes (e.g., children, the elderly, patients with osteomyelitis, etc.), pharmacokinetic/pharmacodynamic studies and prospective clinical trials are needed to establish appropriate therapeutic targets.

The impact of serum vancomycin levels and minimum inhibitory concentrations of methicillin-resistant Staphylococcus aureus on mortality in patients with nosocomial pneumonia

BACKGROUND

Vancomycin is the treatment of choice for methicillin-resistant Staphylococcus aureus (MRSA) infections; however, treatment failure is not uncommon, even when the minimum inhibitory concentration (MIC) of the MRSA strain is within the susceptible range for vancomycin.

OBJECTIVE

To describe the relationship between molecular markers such as the mecA and agrII genes, serum vancomycin levels and vancomycin MICs, and the 30-day mortality rate of patients with nosocomial MRSA pneumonia in an intensive care unit (ICU).

METHODS

The present study was a prospective cohort study including all patients with MRSA hospital-acquired pneumonia or ventilator-associated pneumonia who were admitted to the ICU of a tertiary care hospital between June 2009 and December 2011. The MIC for vancomycin was determined using the E-test and broth microdilution methods. Variables analyzed included age, sex, comorbid conditions, serum vancomycin trough concentration, the Acute Physiology and Chronic Health Evaluation II (APACHE) score and the presence of the agrII gene. The primary outcome was mortality at 30 days.

RESULTS

Thirty-six (42.4%) patients died within 30 days of the index MRSA culture. A multiple regression analysis that included the variables of MIC (determined using the E-test or broth microdilution methods), APACHE II score, serum vancomycin level and the presence of agrII revealed that only the APACHE II score was related to the 30-day mortality rate (P=0.03). Seven patients (9.0%) with isolates exhibiting an MIC ≥1.5 μg/mL according to the E-test method died, and nine patients (11.6%) survived (P=0.76). Of the patients for whom MICs were determined using the broth microdilution method, 11 (14.1%) patients with MICs of 1.0 μg/mL died, and 16 (20.5%) survived (P=0.92). The median APACHE II score of survivors was 22.5, and the median score of nonsurvivors was 25.0 (P=0.03). The presence of the agrII gene was not related to the 30-day mortality rate.

CONCLUSIONS

Patients with severe hospital-acquired pneumonia presented with MRSA isolates with low to intermediate vancomycin MICs in the ICU setting. At the Hospital de Clínicas de Porto Alegre (Porto Alegre, Brazil), the 30-day mortality rate was high, and was similar among patients with severe hospital-acquired pneumonia infected with MRSA isolates that exhibited MICs of ≤1.5 μg/mL determined using the E-test method and ≤1.0 μg/mL determined using the broth microdilution method in those who achieved optimal serum vancomycin levels. The APACHE II scores which provides an overall estimate of ICU mortality were independently associated with mortality in the present study, regardless of the MICs determined. Molecular markers, such as the agrII gene, were not associated with higher mortality in the present study.

Effects of aggregate and individual antibiotic exposure on vancomycin MICs for Staphylococcus aureus isolates recovered from pediatric patients

We evaluated the evolution of vancomycin MICs for Staphylococcus aureus and their relationship with vancomycin use among hospitalized children. S. aureus isolates recovered from sterile sites were prospectively tested for vancomycin susceptibility using the Etest between 1 April 2000 and 31 March 2008. Vancomycin MICs were grouped into three categories: ≤ 1, 1.5, and 2 μg/ml. The association between vancomycin MICs and aggregate vancomycin use and individual patient vancomycin exposure 6 months prior to the documented infection was assessed. The geometric mean values for vancomycin MICs for S. aureus fluctuated over time without a significant trend (P = 0.146). Of the 436 patients included in the study, 363 (83%) had methicillin-susceptible S. aureus (MSSA) and 73 (17%) had methicillin-resistant S. aureus (MRSA) infections. The rate of isolates with a vancomycin MIC of 2 μg/ml increased from 4% (2 of 46) in 2000 to 2001 to 24% (11 of 46) in 2007 to 2008, despite a decrease in vancomycin use (r = -0.11; P = 0.825). The percentage of isolates with a vancomycin MIC of 2 μg/ml was higher for MRSA (15%; 11 of 73) than for MSSA strains (5.2%; 19 of 363) (χ(2) = 9.2; P = 0.01). Individual patient vancomycin exposure was not associated with a higher vancomycin MIC. In the unadjusted model, in which we compared patients with S. aureus infections with MICs of ≤ 1 μg/ml, the odds ratios of exposure rates for patients with isolates with MICs of 1.5 μg/ml and 2 μg/ml were 1.02 (P = 0.929) and 1.13 (P = 0.767), respectively. In our experience, the geometric means of vancomycin MICs from S. aureus isolates recovered from hospitalized children oscillated over time and were not associated with previous individual patient vancomycin exposure or aggregate vancomycin use.

Stimulation of platelet apoptosis by balhimycin

Glycopeptides, such as vancomycin, are powerful antibiotics against methicillin-resistant Staphylococcus aureus. Balhimycin, a glycopeptide antibiotic isolated from Amycolatopsis balhimycina, is similarly effective as vancomycin. Side effects of vancomycin include triggering of platelet apoptosis, which is characterized by cell shrinkage and by cell membrane scrambling with phosphatidylserine exposure at the cell surface. Stimulation of apoptosis may involve increase of cytosolic Ca(2+) activity, ceramide formation, mitochondrial depolarization and/or caspase activation. An effect of balhimycin on apoptosis has, however, never been reported. The present study thus tested whether balhimycin triggers platelet apoptosis. Human blood platelets were treated with balhimycin and cell volume was estimated from forward scatter, phosphatidylserine exposure from annexin V-binding, cytosolic Ca(2+) activity from fluo-3AM fluorescence, ceramide formation utilizing antibodies, mitochondrial potential from DiOC6 fluorescence, and caspase-3 activity utilizing antibodies. As a result, a 30 min exposure to balhimycin significantly decreased cell volume (≥1 μg/ml), triggered annexin V binding (≥1 μg/ml), increased cytosolic Ca(2+) activity (≥1 μg/ml), stimulated ceramide formation (≥10 μg/ml), depolarized mitochondria (≥1 μg/ml) and activated caspase-3 (≥1 μg/ml). Cell membrane scrambling and caspase-3 activation were virtually abrogated by removal of extracellular Ca(2+). Cell membrane scrambling was not significantly blunted by pancaspase inhibition with zVAD-FMK (1μM). In conclusion, balhimycin triggers cell membrane scrambling of platelets, an effect dependent on Ca(2+), but not on activation of caspases.

Impact of vancomycin minimum inhibitory concentration on clinical outcomes of patients with vancomycin-susceptible Staphylococcus aureus infections: a meta-analysis and meta-regression

Although the vancomycin minimum inhibitory concentration (VMIC) susceptibility breakpoint for Staphylococcus aureus was recently lowered to ≤2 mg/L, it is argued that isolates in the higher levels of the susceptible range may bear adverse clinical outcomes. Clinical outcomes (all-cause mortality and treatment failure) of patients with S. aureus infections by 'high-VMIC' (conventionally defined as VMIC >1 mg/L but ≤2 mg/L) and 'low-VMIC' (VMIC≤1 mg/L) isolates were compared by performing a systematic review and meta-analysis. The effect of potential confounders was assessed by univariate meta-regression analyses. In total, 33 studies (6210 patients) were included. Most studies were retrospective (28/33), used the Etest (22/33) and referred to meticillin-resistant S. aureus (MRSA) infections (26/33) and bacteraemia (23/33). Irrespective of VMIC testing method, meticillin resistance and site of infection, the high-VMIC group had higher mortality [relative risk (RR)=1.21 (95% confidence interval 1.03-1.43); 4612 patients] and more treatment failures [RR=1.67 (1.26-2.21); 2049 patients] than the low-VMIC group. The results were not affected by the potential confounders and were reproduced in the subset of patients with MRSA infections [mortality, RR=1.19 (1.02-1.40), 2956 patients; treatment failure, RR=1.69 (1.26-2.25), 1793 patients]. In conclusion, infection by vancomycin-susceptible S. aureus with VMIC>1mg/L appears to be associated with higher mortality than VMIC≤1mg/L. Further research is warranted to verify these results and to assess the impact of VMIC on meticillin-susceptible S. aureus infections. Evaluation of alternative antimicrobial agents also appears justified.

Intrathoracic irrigation with arbekacin for methicillin-resistant Staphylococcus aureus empyema following lung resection

OBJECTIVES

Empyema is a well-known complication following lung resection. In particular, empyema caused by methicillin-resistant Staphylococcus aureus (MRSA) is difficult to treat. Here, we present our experience of MRSA empyema treated with local irrigation using arbekacin.

METHODS

Six patients consisted of 4 males and 2 females with an average age of 65.7 years. They developed MRSA empyema following lung resection and were treated at our institution between 2007 and 2011. Cases comprised four primary and one metastatic lung cancer, and 1 patient was a living lung transplantation donor. The surgical procedure consisted of four lobectomies, one segmentectomy and one wedge resection. After diagnosis of MRSA empyema, anti-MRSA drugs were administered intravenously in all cases. In addition, arbekacin irrigation at a dose of 100 mg dissolved in saline was performed after irrigation with saline only.

RESULTS

The average number of postoperative days for the diagnosis of MRSA empyema was 13 (range 4-19). The period of irrigation ranged from 6 to 46 days. Arbekacin irrigation did not induce nephrotoxicity or other complications, and no bacteria resistant to arbekacin was detected in the thoracic cavity. We re-operated on 1 case because he had pulmonary fistula and severe wound infection. At the time of removing the thoracic catheter, MRSA in the pleural effusion disappeared completely in 3 patients. The period until MRSA concentration in the pleural effusion became negative after starting arbekacin irrigation ranged from 4 to 9 days. In the remaining cases, in which MRSA did not disappear, the catheter was removed because of no inflammatory reaction after stopping irrigation and clamping the catheters. All patients were discharged from our institution without thoracic catheterization and no patients had relapsed during the follow-up period ranging from 6 to 44 months.

CONCLUSIONS

Irrigation of the thoracic cavity with arbekacin proved to be an effective, safe and readily available method for treating MRSA empyema following lung resection.

Vancomycin MICs of the resistant mutants of S. aureus ATCC43300 vary based on the susceptibility test methods used

Clinical failures with vancomycin against meticillin-resistant Staphylococcus aureus (MRSA) infections have challenged vancomycin's standing as a first-line antimicrobial for these infections. Conventional MIC tests were not predictive of the in vivo therapeutic effect of vancomycin. Thus, we tested the susceptibility for the resistant mutants in the mutant selection window of S. aureus ATCC43300 (a MRSA strain) by three different MIC-testing methods in this paper. The MIC of vancomycin was estimated at 2 μg ml⁻¹ on the Mueller-Hinton agar (MHA) plate only for the resistant mutant that was selected from the plate of vancomycin concentration 12 μg ml⁻¹. The obvious changes of susceptibility testing were found between the resistant mutants and S. aureus ATCC43300 on the Brain-Heart Infusion Agar (BHIA) plates. There were subtle changes in the MIC trend within the susceptible range with the result of Etest for the resistant mutants. The susceptibility for the subcultures of resistant mutants would fall back when the external drug environment disappeared. In comparison with the S. aureus ATCC43300, sequence analysis revealed that there were no mutations in the staphylococcal protein A (spa) sequencing of the resistant mutants. The spa tape is t421 for all isolates.

Vancomycin dosing in critically ill patients: robust methods for improved continuous-infusion regimens

Despite the development of novel antibiotics active against Gram-positive bacteria, vancomycin generally remains the first treatment, although rapidly achieving concentrations associated with maximal efficacy provides an unresolved challenge. The objective of this study was to conduct a population pharmacokinetic analysis of vancomycin in a large population of critically ill patients. This was a retrospective data collection of 206 adult septic critically ill patients who were administered vancomycin as a loading dose followed by continuous infusion. The concentration-versus-time data for vancomycin in serum was analyzed by a nonlinear mixed-effects modeling approach using NONMEM. Monte Carlo simulations were performed using the final covariate model. We found that the best population pharmacokinetic model consisted of a one-compartment linear model with combined proportional and additive residual unknown variability. The volume of distribution of vancomycin (1.5 liters/kg) was described by total body weight and clearance (4.6 liters/h) by 24-hour urinary creatinine clearance (CrCl), normalized to body surface area. Simulation data showed that a 35-mg/kg loading dose was necessary to rapidly achieve vancomycin concentrations of 20 mg/liter. Daily vancomycin requirements were dependent on CrCl, such that a patient with a CrCl of 100 ml/min/1.73 m² would require at least 35 mg/kg per day by continuous infusion to maintain target concentrations. In conclusion, we have found that higher-than-recommended loading and daily doses of vancomycin seem to be necessary to rapidly achieve therapeutic serum concentrations in these patients.