Background. Data suggest that higher doses of vancomycin can increase the risk of nephrotoxicity. No study has been undertaken to determine the pharm

Increasing antimicrobial resistance and medical device-related infections have led to a renewed interest in phage therapy as an alternative or adjunct to conventional antimicrobials. Expanded access and compassionate use cases have risen exponentially but have varied widely in approach, methodology, clinical situations in which phage therapy might be considered, dosing, route of administration, and outcomes.

The delivery of personalized antimicrobial therapy is a critical component in the treatment of patients with invasive infections. Vancomycin, the drug of choice for infections due to methicillin-resistant Staphylococcus aureus, requires the use of therapeutic drug monitoring (TDM) for delivery of optimal therapy. Current guidance on vancomycin TDM includes the measurement of a trough concentration as a surrogate for achieving an AUC to minimum inhibitory concentration (MIC) by broth microdilution (AUC/MICBMD) ratio≥400. Although trough-only monitoring has been widely integrated into clinical practice, there is a high degree of inter-individual variability between a measured trough concentration and the actual AUC value. The therapeutic discordance between AUC and trough may lead to suboptimal outcomes among patients with infections due to less susceptible pathogens or unnecessarily increase the probability of acute kidney injury (AKI) in others. Given the potentially narrow vancomycin AUC range for optimal effect and minimal AKI, clinicians need a "real-time" system to predict accurately the AUC with limited pharmacokinetic (PK) sampling. This article reviews two innovative approaches for calculating the vancomycin AUC in clinical practice based on one or two drug concentrations. One such approach involves the use of Bayesian computer software programs to estimate the "true" vancomycin AUC value with minimal PK sampling and provide AUC-guided dosing recommendations at the bedside. An alternative involves use of two concentrations (peak and trough) and simple analytic equations to estimate AUC values. Both approaches provide considerable improvements over the current trough-only concentration monitoring method.

This study quantified mortality associated with serious infections caused by carbapenem-resistant (CRE) and carbapenem-susceptible Enterobacteriaceae (CSE). A systematic literature review was conducted, evaluating outcomes in hospitalized patients with CRE infections from a blood, urinary, pulmonary, or intra-abdominal source. A meta-analysis (MA) calculating odds ratios (ORs) for mortality was performed. Twenty-two studies met the criteria for inclusion in the MA: 12 included mortality data for CRE vs CSE populations. Compared with CSE, CRE was associated with a significantly higher risk of overall mortality (OR, 3.39; 95% confidence interval [CI], 2.35–4.89), as was monotherapy (vs combination therapy) treatment of patients with CRE infections (OR, 2.19; 95% CI, 1.00–4.80). These results document the increased mortality associated with serious CRE infections compared with CSE infections among hospitalized adults. It will be important to reevaluate the mortality in CRE and CSE populations, especially among patients who receive early appropriate therapy, as new antibiotics become available.

Using a valid Bayesian method to estimate vancomycin exposure profiles, the findings establish the critical importance of area under the curve to minimum inhibitory concentration ratios during the first two days of therapy for patients with MRSA bloodstream infections. Background. Contemporary vancomycin dosing schemes are designed to achieve an area under the curve (AUC) to minimum inhibitory concentration (MIC) ratio of ≥400. However, scant clinical data exist to support this target and available data relied on pharmacokinetic formulas based on daily vancomycin dose and estimated renal function (demographic pharmacokinetic model) to estimate AUCs. Methods. A cohort study of hospitalized, adult, nondialysis patients with methicillin-resistant Staphylococcus aureus bloodstream infections treated with vancomycin was performed to quantitatively evaluate the relationship between vancomycin exposure and outcomes. Bayesian techniques were used to estimate vancomycin exposure profile for day 1 and 2 of therapy for each patient based on their dosing schedule and collected concentrations. Classification and Regression Tree (CART) analysis was used to identify day 1 and 2 exposure thresholds associated with an increased risk of failure. Failure was defined as 30-day mortality, bacteremia was ≥7 days, or recurrence. Results. During the study period, 123 cases met criteria. Failure was uniformly less pronounced (approximately 20% less in absolute value) in patients who achieved the CART-derived day 1 and 2 thresholds for AUC/MIC by broth microdilution and AUC/MIC by Etest. In the multivariate analyses, all risk ratios were approximately 0.5 for all CART-derived AUC/MIC exposure thresholds, indicating that achievement of CART-derived AUC/MIC exposure thresholds was associated with a 2-fold decrease in failure. Conclusions. These findings establish the critical importance of daily AUC/MIC ratios during the first 2 days of therapy. As with all observational studies, these findings should be interpreted cautiously and validated in a multicenter randomized trial before adoption into practice.

Vancomycin is the most commonly administered antibiotic in hospitalized patients, but optimal exposure targets remain controversial. To clarify the therapeutic exposure range, this study evaluated the association between vancomycin exposure and outcomes in patients with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. This was a prospective, multicenter (n = 14), observational study of 265 hospitalized adults with MRSA bacteremia treated with vancomycin. The primary outcome was treatment failure (TF), defined as 30-day mortality or persistent bacteremia ≥7 days. Secondary outcomes included acute kidney injury (AKI). The study was powered to compare TF between patients who achieved or did not achieve day 2 area under the curve to minimum inhibitory concentration (AUC/MIC) thresholds previously found to be associated with lower incidences of TF. The thresholds, analyzed separately as co-primary endpoints, were AUC/MIC by broth microdilution ≥650 and AUC/MIC by Etest ≥320. Treatment failure and AKI occurred in 18% and 26% of patients, respectively. Achievement of the prespecified day 2 AUC/MIC thresholds was not associated with less TF. Alternative day 2 AUC/MIC thresholds associated with lower TF risks were not identified. A relationship between the day 2 AUC and AKI was observed. Patients with day 2 AUC ≤515 experienced the best global outcomes (no TF and no AKI). Higher vancomycin exposures did not confer a lower TF risk but were associated with more AKI. The findings suggest that vancomycin dosing should be guided by the AUC and day 2 AUCs should be ≤515. As few patients had day 2 AUCs <400, further study is needed to define the lower bound of the therapeutic range.