bluuebunny/crossref_metadata_2025_split huggingface dataset:
1533. Is Cation-Adjusted Mueller–Hinton Broth (CAMHB) Appropriate for Metallo-β-lactamase (MBL) Susceptibility Testing? Novel Insights in In Vitro–In Vivo Discordance Among MBL-Producing Enterobacteriaceae
Authors: Asempa Tomefa E , Abdelraouf Kamilia , Nicolau David P 
Published: October 2019

Abstract

Background
MBLs, which require Zn for catalytic activity, are a major contributor to high-level β-lactam resistance when tested using conventional CAMHB. We have previously reported marked reductions in meropenem (MEM) MICs in Zn-depleted media (Chelex-CAMHB and EDTA-CAMHB; Zn [C] <0.002 mg/L) compared with conventional CAMHB (Zn [C] 0.959 mg/L) against a variety of MBL-producing isolates, whereas Zn-depletion had no impact on levofloxacin (LVX) MICs (ASM Microbe 2019, San Francisco. Abstract P508). To explore in vivo implications, we evaluated the efficacy of MEM human simulated regimen (HSR) against MBL-producing isolates in a murine pneumonia model. In addition, LVX HSR was examined for model validation.

Methods
Nine MBL-producing isolates (NDM, n = 5; VIM, n = 2; IMP, n = 2) were utilized. CAMHB, Chelex-CAMHB, and EDTA-CAMHB MEM MICs ranged from 16 to > 64, ≤0.0625 to 0.5, and ≤ 0.0625 to 0.5 mg/L, respectively. LVX MICs ranged from ≤ 0.0625 – > 64 mg/L. Neutropenic lung-infected ICR mice received a MEM HSR of 2g q8h [1.5 hours infusion], 2 lower MEM exposures or LVX 750 mg q24h HSR. Zn [C] were determined in the epithelial lining fluid (ELF) of infected mice.

Results
LVX displayed predictable in vivo efficacy consistent with its phenotypic profile irrespective of the media utilized for MIC testing (figure). Despite attaining zero %T> MIC using values generated in CAMHB, MEM HSR produced marked bacterial reductions against all MBL-producing isolates (figure). Reductions in MEM exposures produced bacterial killing concordant with its pharmacodynamic profile using Zn-depleted CAMHB MIC values. Zn [C] in infected murine ELF were undetectable, i.e., <0.002 mg/L.

Conclusion
Our results indicate that MEM in vivo efficacy is best represented by the pharmacodynamic profile generated using MICs determined in Zn-depleted media for MBL-producing Enterobacteriaceae. These observations are consistent with the case reports describing positive outcomes in MBL-infected patients following treatment with carbapenems (Infection 2018;46:1–13). Our translational data suggest that the use of conventional CAMHB for MBL susceptibility testing is inappropriate in distinguishing meaningful in vivo resistance given that Zn [C] are supraphysiologic in conventional CAMHB and negligible at infection sites.

Disclosures
All authors: No reported disclosures.
1537. Multicenter Study with Therapeutic Drug Monitoring (TDM) of Voriconazole (VRCZ) in Japanese Patients
Authors: Ueda Takashi , Takesue Yoshio , Hamada Yukihiro , Fukunaga Keiko , Ikegame Kazuhiro , Ebihara Fumiya , Kimura Toshimi , Nakajima Kazuhiro , Miyazaki Taiga , Nakada-Motokawa Nana , Nagao Miki , Kawamura Hideki , Shigemi Akari , Miyazaki Yoshitsugu 
Published: October 2019

Abstract

Background
TDM of VRCZ might be useful, especially in Asian people because of CYP2C19 genetic polymorphisms. However, limited data are available because of the small sample size.

Methods
Patients who received VRCZ and had TDM were reviewed retrospectively at five institutions. Adequate VRCZ dosage was defined as a loading dose of 5–6 ± 0.5 mg/kg twice daily followed by a maintenance dose of 3–4 ± 0.5 mg/kg twice daily. For prophylaxis, the loading dose was left to the physician’s discretion. Optimal timing of TDM was defined as 4–7 days after starting therapy. Patients with adequate dosing and optimal timing of TDM were evaluated for analysis of trough levels (Cmin). Target Cmin was set at 1–5 µg/mL.

Results
The study included 584 patients (treatment: 402; prophylaxis: 182). TDM was conducted on days 4–7 in 66.5% of patients (>7, 30.2%). A low adequate dosage (44.5%) was observed for treatment mainly because of a low performance of the loading dose (46.8%). Achievement of target Cmin was obtained in 62.7% (>5 µg/mL, 32.2%) in the treatment group and in 67.6% (11.0%) in the prophylaxis group. Seventy-one of 81 (81.7%) patients who required a dose reduction reached target Cmin by the second TDM. In 38 patients whose dose was not altered at oral switching, Cmin was significantly reduced from 2.5 ± 1.6 to 1.2 ± 1.3 μg/mL (P = 0.002), which indicated the necessity of TDM after oral switching. Hepatotoxicity occurred in 4.6% and visual symptoms in 7.9% of patients. Visual symptoms resolved without discontinuation of VRCZ in 73.9% of patients. Because of dosage adjustment based on TDM, high Cmin did not cause hepatotoxicity. However, the incidence of visual symptoms was significantly higher in patients with a high Cmin (12.7% vs. 5.4%, P = 0.002).

Conclusion
One-third of Japanese patients who underwent VRCZ treatment with a loading dose showed high Cmin. Occurrence of hepatotoxicity was prevented with alteration of dosage in these patients (AMED, JP18fk0108045).

Disclosures
All authors: No reported disclosures.
1541. A Novel and Fast Liquid Chromatography Method for Determination of Fluoroquinolones in Human Plasma
Authors: Yildirim Sercan , Nur Karakoc Hanife , Yasar Ahmet , Koksal Iftikhar 
Published: October 2019

Abstract

Background
Fluoroquinolones (FQs) are frequently used antimicrobial agents. Considering that the FQs exhibit concentration-dependent bactericidal activity, concentrations of FQs in the biological fluids must be monitored to ensure treatment success. The literature search revealed that there is no method for the determination of levofloxacin (LEV), ciprofloxacin (CIP), moxifloxacin (MOX), and gemifloxacin (GEM) in plasma up to date. Consequently, the aim of this study was to develop and validate a new high-performance liquid chromatography (HPLC) method for determination of these FQs in plasma and evaluate effects of concomitant drugs on plasma FQ concentrations of patients.

Methods
Blank plasma samples spiked with FQs were employed for method validation studies. Validation studies were conducted in accordance with the recommendations of the US FDA. In order to demonstrate feasibility of method, 5 patients with polypharmacy, receiving orally CIP, LEV, or MOX as part of their treatment were included in the study. Blood samples were collected at two different times, just before and 2 hours after the second drug administration.

Results
The separation of FQs was accomplished within 7.5 minutes. The method was linear in the range of 0.1–10 µg/mL with the correlation coefficient >0.99. The RSD at four concentration levels (0.1, 0.3, 4, and 8 µg/mL) was less than 7% with accuracy in the range of 91.8–111.9%.The method was applied to the determination of CIP, LEV, and MOX levels in plasma samples of 5 patients with polypharmacy. Determined CIP and LEV levels were in accordance with literature. On the other hand, MOX concentration 2 hours after administration in plasma of one patient was found to be 6.1 ± 0.1 µg/mL which was higher than previously reported maximum plasma concentration of MOX (4.5 µg/mL). The patient had hypoalbuminemia and MOX is approximately 50% bound to serum proteins. Due to low level of albumin, the level of free MOX in plasma may be increased.

Conclusion
A simple, fast, and reliable HPLC method was developed and validated for the determination of LEV, CIP, MOX, and GEM in plasma. It is suitable therapeutic drug monitoring of these FQs and can be applied to other pharmacokinetic and toxicological studies.

Disclosures
All authors: No reported disclosures.
1542. The Evaluation of the In Vitro Synergy of Colistin in Combination with Meropenem and Tigecycline against 50 Multi-Drug-resistant Acinetobacter baumannii strains
Authors: Abdul-Mutakabbir Jacinda , Yim Juwom , Nguyen Logan , Kebriaei Razieh , Stamper Kyle , Maassen Philip , Kaye Keith S , Rybak Michael J 
Published: October 2019

Abstract

Background
Acinetobacter baumannii possess inherent and acquired antibiotic resistance mechanisms that have rendered most antibiotics, including carbapenems, inactive. Colistin (COL) has risen as salvage therapy against these organisms due to its retained activity against A. baumannii. However, COL monotherapy is often met with suboptimal outcomes. Recently, combination therapy with COL and meropenem (MEM) or tigecycline (TGC) has been shown to be effective in eradicating multi-drug-resistant A. baumannii infections. The objective of this study was to further evaluate the efficacy of COL in combination with MEM or TGC against 50 multi-drug-resistant A. baumannii strains.

Methods
Fifty carbapenem-resistant A. baumannii strains were evaluated using combination minimum inhibitory concentration (MIC) testing and time-kill analysis (TKA). Single-drug MIC testing was performed for each strain by broth microdilution. Combination MIC testing was performed for COL+MEM and COL+TGC. Each strain was evaluated via 24-hour TKA to assess the synergistic capabilities of COL+MEM, and COL+TGC. Synergy was defined as a ≥ 2-log reduction CFU/mL in either combination from the most active single agent, while bactericidal activity was defined as a ≥ 3-log reduction CFU/mL of either combination from the initial inoculum.

Results
All 50 strains were resistant to MEM and TGC with MICs ≥ 64 µg/mL and ≥ 4 µg/mL respectively; while 3 strains were resistant to COL, MICs ≥ 2 µg/mL. MEM and TGC MIC values were reduced as much as 128-fold (median 2-fold) and 32-fold (median 2-fold),, respectively, in the presence of subinhibitory COL. COL MIC values were reduced as much as 512-fold (median 4-fold) from baseline in the presence of subinhibitory MEM, and as high as 16-fold (median 2-fold) in the presence of TGC. In TKAs, COL+MEM was synergistic in 45/50 (90%) strains and bactericidal against 43/50 (86%) strains. COL+TGC TKAs revealed synergy in 32/50 (64%) strains, and bactericidal activity against 28/50 (56%) strains.

Conclusion
The combinations of COL+MEM and COL+TGC demonstrate promise in combating highly resistant A. baumannii. Further research is mandated to explore other combinations that are capable of eradicating multi-drug-resistant A. baumannii.

Disclosures
All authors: No reported disclosures.
1543. Ceftaroline Model-based Dose Individualization in an Infant with Kidney Disease and Mediastinitis
Authors: Murphy Mark , Tang-Girdwood Sonya , Tang Peter , Rebecca Brady C , Mizuno Tomoyuki , Vinks Alexander 
Published: October 2019

Abstract

Background
Options for the treatment of infections caused by resistant gram-positive bacteria are limited in children with kidney disease. Ceftaroline (CFD) may be an attractive option but dosing recommendations are not available for children with renal dysfunction. We present a case of pharmacokinetics (PK) model-based individualization of CFD in an infant with kidney disease and mediastinitis. A 5-week-old infant with a hypoplastic left side of the heart developed mediastinitis following a Norwood and BT shunt. Blood and chest washout cultures grew S. epidermidis. Vancomycin therapy led to acute kidney injury (AKI) (eGFR ~15mL/minute) and therefore, CFD was initiated at 8 mg/kg every 12 hours. The model-based clinical service was consulted to assist with dosing.

Methods
Plasma levels were drawn on day 2 and 10 of CFD. CFD concentrations were determined by HPLC. The pharmacodynamic (PD) target used the MIC of the isolate, 1 µg/mL, and assumed drug diffusion into the mediastinum at 20% of plasma. The PD target was ƒT>MIC at 100%. Individual PK parameters were estimated using Bayesian estimation with MWPharm++ (Mediware, the Netherlands).

Results
CFD dosing of 8 mg/kg every 12 hours resulted in concentrations well above the target. The trough level was 10 times higher than levels seen in clinical trials. Repeat levels were checked on day 10 due to improved renal function (eGFR 30 mL/minute) and changes in volume status. Changes in both clearance and volume were noted. ƒT>MIC was maintained 100% during dosing intervals. We dose optimized CFD to achieve the target while minimizing potential toxicity with long-term use. A new dosing regimen, 5.4 mg/kg every 8 hours, was started on day 12 and continued for 6 weeks.

Conclusion
This is the first case report of CFD use in a child with AKI. Though initial dosing resulted in high concentrations, no adverse effects were noted. Successful treatment was completed with a final dosing regimen of 5.3 mg/kg every 8 hours, below the recommended 8 mg/kg every 8 hours. Lower dosing was needed to decrease high drug exposure due to the decreased clearance. This case also demonstrated the feasibility of PK model-based precision dosing within 48 hours, and documented utility in the setting of changes in renal function. Further PK/PD studies are needed in children with renal dysfunction.

Disclosures
All authors: No reported disclosures.
1552. Correlation Between Vancomycin Serum Trough Concentrations and Area Under the Curve in Pediatric Patients
Authors: Weaver Krista , Kumar Madan , Nelson Allison , Bhagat Palak 
Published: October 2019

Abstract

Background
Despite years of experience with vancomycin (VAN), the optimal method to monitor VAN therapy in pediatric patients is still unknown. Recent pediatric data indicate serum trough concentrations lower than 10–20 mg/L or 15–20 mg/L based on indication may achieve an AUC24> 400 mg hours/L. The primary study objective was to compare AUC24 to goal VAN serum trough concentrations (STC).

Methods
A retrospective chart review of pediatric patients who received intravenous VAN June 1, 2018 to December 31, 2018 was completed. AUC24 was calculated using a trapezoidal method with 2 steady-state serum concentrations. A serum peak concentration was drawn 1 hour and 15 minutes following the end of infusion and an STC was drawn 30 minutes prior to infusion.

Results
During 25 admissions, 12 patients had a first AUC24 at goal and 13 patients had a first AUC24 below goal. Of 41 AUC24 calculations, 27 AUC24s were ≥400 mg hours/L (group 1), and 14 AUC24s were <400 mg hours/L (group 2). Median AUC24 was 561 mg hours/L for group 1 vs. 344.5 mg hours/L for group 2 (P < 0.001). Correlating Cmin and Ctrough (Ctr) for group 1 and group 2 were 12 mg/L and 13.5 mg/L vs. 6.4 mg/L and 7.3 mg/L, respectively (P < 0.001). Figure 1 shows the pharmacokinetic parameters for each group. Spearman correlation between AUC24 and Cmin was 0.87. Of the 35 subtherapeutic VAN STCs, 20 (57.1%) achieved an AUC24 ≥400 mg hours/L (P = 0.08). Subgroup analysis of AUC24 400–600 mg hours/L showed a median AUC24 of 519 mg hours/L with correlating Cmin and Ctr of 10.6 mg/L and 11.9 mg/L, respectively. The MIC was <1 in 90.9% of cases (Figure 2). The mean VAN dose required to achieve an AUC24 ≥400 mg hours/L was 77.7 mg/kg/day; dosing frequency did not appear to affect AUC24 outcome. Time to culture clearance was 2 days in group 1 and 6.5 days in group 2 (P = 0.24). No cases of nephrotoxicity were identified despite AUC24 values ranging from 265–1294 mg hours/L.

Conclusion
AUC24 monitoring using a 2-sample trapezoidal method was successfully implemented at this institution. The results of this study align with previous pediatric studies, supporting the use of lower serum trough concentration goals of 10–15 mg/L.

Disclosures
All authors: No reported disclosures.
1553. Human-Simulated Pharmacokinetic Profiles of Cefiderocol and Meropenem Are Conserved in Murine Models of Thigh Infection With or Without Iron Overload
Authors: Kidd James M , Abdelraouf Kamilia , Nicolau David P 
Published: October 2019

Abstract

Background
A translational murine model of thigh infection with comorbid iron overload was previously developed to study the efficacy of iron-dependent siderophore-antibiotic conjugates under conditions where the hypoferremic response of innate immunity may be compromised. Given the potential for functional organ damage from excessive tissue iron, which could alter the pharmacokinetic (PK) profiles of antibiotics being compared for efficacy using this model, the effects of iron overload on a siderophore-β-lactam conjugate, cefiderocol (CFDC), and a non-siderophore β-lactam, meropenem (MEM), were studied.

Methods
Female CD-1 mice received iron dextran (Fe-D) 100 mg/kg intraperitoneally for 14 days as previously shown to produce vastly supranormal iron concentrations in serum, liver, and spleen (ASM Microbe 2019 abstract HMB-373). Age-matched control mice were not dosed with Fe-D. Mice were rendered neutropenic. On day 15, both thighs of iron-overloaded and control mice were inoculated intramuscularly with Acinetobacter baumannii suspensions of 107 CFU/mL. Two hours after inoculation, mice in each model were dosed with previously developed human-simulated regimens (HSR) of CFDC or MEM simulating human PK profiles after doses of 2g q8h (3 hours infusion) for both drugs. At 4 time points per regimen, 6 mice per model were sacrificed for blood collection. Plasma total MEM and CFDC concentrations were measured with HPLC and LC-MS-MS, respectively. Free concentrations were calculated with murine protein binding. At each time point, mean free concentrations in both models were compared using Student’s t-test.

Results
Observed murine-free plasma concentrations ± 95% CI of CFDC and MEM are overlaid with simulated human and murine profiles in the figure. In both models, these regimens approximated human exposures after clinical doses. For all time points and both drugs, concentrations were not significantly different (P > 0.05) between models with or without iron overload.

Conclusion
Iron overload did not significantly alter PK profiles of a siderophore-β-lactam conjugate, CFDC, or a non-siderophore β-lactam, MEM. These data support the use of CFDC and MEM HSR for pharmacodynamic studies utilizing both iron-overloaded and standard murine thigh infection models.

Disclosures
All authors: No reported disclosures.
1571. Evaluation of a Single Post First Dose Vancomycin Level to Achieve a Goal Vancomycin AUC
Authors: Hurley Evan , Ebert Steven C 
Published: October 2019

Abstract

Background
The 24-hour area under the serum concentration–time curve (AUC24) is the most defensible measure to predict the effectiveness and toxicity of vancomycin. The optimal method and time point to assess and optimize AUC24, however, have yet to be determined. Measuring a trough concentration at steady state has been the traditional method of monitoring vancomycin, but trough is unreliable at estimating AUC24. More accurate methods for estimating AUC24 are paired sample analysis, or a single optimally timed sample combined with population pharmacokinetics. We wished to optimize AUC24 prior to steady state for earlier goal attainment, thereby decreasing risk of treatment failure, resistance, and/or nephrotoxicity. A single optimally timed single post first dose level may be used to estimate drug clearance and thereby AUC. Based on the post first dose concentration and a population pharmacokinetic model, clearance is calculated, and the dosing regimen can be adjusted to achieve a desired AUC24. Our institution has enabled pharmacists to obtain post first dose vancomycin levels and make early dose adjustments. The aim of this project is to monitor the accuracy of this method and the outcomes of patients who have received post first dose vancomycin levels and subsequent dose assessment/adjustment.

Methods
Single-center cohort study via electronic chart review of patients with vancomycin therapeutic dose monitoring based on post first dose vancomycin levels obtained between January 2019 and April 2019.

Results
41 patients were dosed and monitored based on post first dose vancomycin levels. Fourteen patients (34%) required dose adjustments based on the post first dose level. Accuracy of assessment was determined in 15 patients (37%) via a steady-state level used to measure vancomycin clearance and AUC24. At steady-state following dose assessment 14/15 (93%) patients had desired targeted goal AUC24. Only two patients (5%) had greater than a 50% increase in baseline serum creatinine.

Conclusion
Post first dose-level analysis resulted in dose regimen modifications in one-third of patients. This consistently allowed the attainment of goal AUC24 at steady-state.

Disclosures
All authors: No reported disclosures.
1573. Population Pharmacokinetic Analyses for Cefepime in Adult and Pediatric Patients
Authors: Liu Jiajun , Neely Michael , Lipman Jeffrey , Sime Fekade B , Roberts Jason , Kiel Patrick J , Scheetz Marc H 
Published: October 2019

Abstract

Background
Cefepime (CEF) is commonly used for adult and pediatric infections. Several studies have examined CEF’s pharmacokinetics (PK) in various populations; however, a unifying PK model for adult and pediatric subjects does not yet exist. We developed a combined population model for adult and pediatric patients and validated the model.

Methods
The initial model includes adult and pediatric patients with a rich cefepime sampling design. All adults received 2 g CEF while pediatric subjects received a mean of 49 (SD 5) mg/kg. One- and two-compartment models were considered as base models and were fit using a non-parametric adaptive grid algorithm within the Pmetrics package 1.5.2 (Los Angeles, CA) for R 3.5.1. Compartmental model selection was based on Akaike information criteria (AIC). Covariate relationships with PK parameters were visually inspected and mathematically assessed. Predictive performance was evaluated using bias and imprecision of the population and individual prediction models. External validation was conducted using a separate adult cohort.

Results
A total of 45 subjects (n = 9 adults; n = 36 pediatrics) were included in the initial PK model build and 12 subjects in the external validation cohort. Overall, the data were best described using a two-compartment model with volume of distribution (V) normalized to total body weight (TBW/70 kg) and an allometric scaled elimination rate constant (Ke) for pediatric subjects (AIC = 4,138.36). Final model observed vs. predicted plots demonstrated good fit (population R2 = 0.87, individual R2 = 0.97, Figure 1a and b). For the final model, the population median parameter values (95% credibility interval) were V0 (total volume of distribution), 11.7 L (10.2–14.6); Ke for adult, 0.66 hour−1 (0.38–0.78), Ke for pediatrics, 0.82 hour−1 (0.64–0.85), KCP (rate constant from central to peripheral compartment), 1.4 hour−1 (1.3–1.8), KPC (rate constant from peripheral to central compartment), 1.6 hour−1 (1.2–1.8). The validation cohort has 12 subjects, and the final model fit the data well (individual R2 = 0.75).

Conclusion
In this diverse group of adult and pediatrics, a two-compartment model described CEF PK well and was externally validated with a unique cohort. This model can serve as a population prior for real-time PK software algorithms.

Disclosures
All authors: No reported disclosures.