In-vitro and in-vivo assessment of nirmatrelvir penetration into CSF, central nervous system cells, tissues, and peripheral blood mononuclear cells

Three years after SARS-CoV-2 emerged as a global infectious threat, the virus has become endemic. The neurological complications such as depression, anxiety, and other CNS complications after COVID-19 disease are increasing. The brain, and CSF have been shown as viral reservoirs for SARS-CoV-2, yielding a potential hypothesis for CNS effects. Thus, we investigated the CNS pharmacology of orally dosed nirmatrelvir/ritonavir (NMR/RTV). Using both an in vitro and an in vivo rodent model, we investigated CNS penetration and potential pharmacodynamic activity of NMR. Through pharmacokinetic modeling, we estimated the median CSF penetration of NMR to be low at 18.11% of plasma with very low accumulation in rodent brain tissue. Based on the multiples of the 90% maximal effective concentration (EC90) for SARS-CoV-2, NMR concentrations in the CSF and brain do not achieve an exposure level similar to that of plasma. A median of only 16% of all the predicted CSF concentrations in rats were > 3xEC90 (unadjusted for protein binding). This may have implications for viral persistence and neurologic post-acute sequelae of COVID-19 if increased NMR penetration in the CNS leads to decreased CNS viral loads and decreased CNS inflammation.

Individual meropenem epithelial lining fluid and plasma PK/PD target attainment

It is unclear whether plasma is a reliable surrogate for target attainment in the epithelial lining fluid (ELF). The objective of this study was to characterize meropenem target attainment in plasma and ELF using prospective samples. The first 24-hour T>MIC was evaluated vs 1xMIC and 4xMIC targets at the patient (i.e., fixed MIC of 2 mg/L) and population [i.e., cumulative fraction of response (CFR) according to EUCAST MIC distributions] levels for both plasma and ELF. Among 65 patients receiving ≥24 hours of treatment, 40% of patients failed to achieve >50% T>4xMIC in plasma and ELF, and 30% of patients who achieved >50% T>4xMIC in plasma had <50% T>4xMIC in ELF. At 1xMIC and 4xMIC targets, 3% and 25% of patients with >95% T>MIC in plasma had <50% T>MIC in ELF, respectively. Those with a CRCL >115 mL/min were less likely to achieve >50%T>4xMIC in ELF (P < 0.025). In the population, CFR for Escherichia coli at 1xMIC and 4xMIC was >97%. For Pseudomonas aeruginosa, CFR was ≥90% in plasma and ranged 80%-85% in ELF at 1xMIC when a loading dose was applied. CFR was reduced in plasma (range: 75%-81%) and ELF (range: 44%-60%) in the absence of a loading dose at 1xMIC. At 4xMIC, CFR for P. aeruginosa was 60%-86% with a loading dose and 18%-62% without a loading dose. We found that plasma overestimated ELF target attainment inup to 30% of meropenem-treated patients, CRCL >115 mL/min decreased target attainment in ELF, and loading doses increased CFR in the population.

Making the case for precision dosing: visualizing the variability of cefepime exposures in critically ill adults

OBJECTIVE

To investigate and describe the variability in cefepime exposures among 'real-world', critically ill patients by using population pharmacokinetic modelling and simulations, and with translation of these findings to visualizations.

METHODS

A cohort of adult medical ICU patients who received cefepime with therapeutic drug monitoring was studied. Two compartment models were developed to estimate cefepime clearance (Model 1) and simulate cefepime exposures among 1000 patients, each with identical creatinine clearance of 60 mL/min and receiving a regimen of cefepime 1 gram IV over 30 minutes, every 8 hours (Model 2). Variability in the relationship between cefepime clearance and creatinine clearance (CrCL) was visualized, and a random, representative sample of 10 simulated patients was utilized to illustrate variability in cefepime exposures.

RESULTS

A total of 75 adult medical ICU patients (52% female) and 98 serum cefepime samples were included in the study. Population parameter estimates for cefepime displayed a wide range of variation in Model 1 (CV: 45% to 95%), with low bias at the individual level at 0.226 mg/L but high bias in the population model 10.6 mg/L. Model 2 displayed similar fits, demonstrating that correcting for individual patient creatinine clearance slightly improves the bias of the population model (bias = 4.31 mg/L). Among 10 simulated patients that a clinician would deem similar from a dosing perspective (i.e. equivalent creatinine clearance), maximum concentrations after three simulated doses varied more than 8-fold from 41.2 to 339 mg/L at the 5th and 95th percentiles, and clearance profiles were highly different.

CONCLUSION

Creatinine clearance estimates alone are inadequate for predicting cefepime exposures. Wide variations in cefepime exposure exist among ICU patients, even for those with similar kidney function estimates. Current population adjustment schemes based solely on creatinine clearance will result in unintended high and low exposures leading to safety and efficacy concerns, respectively.

Genomics of Aminoglycoside Resistance in Pseudomonas aeruginosa Bloodstream Infections at a United States Academic Hospital

Pseudomonas aeruginosa frequently becomes resistant to aminoglycosides by the acquisition of aminoglycoside modifying enzyme (AME) genes and the occurrence of mutations in the mexZ, fusA1, parRS, and armZ genes. We examined resistance to aminoglycosides in a collection of 227 P. aeruginosa bloodstream isolates collected over 2 decades from a single United States academic medical institution. Resistance rates of tobramycin and amikacin were relatively stable over this time, while the resistance rates of gentamicin were somewhat more variable. For comparison, we examined resistance rates to piperacillin-tazobactam, cefepime, meropenem, ciprofloxacin, and colistin. Resistance rates to the first four antibiotics were also stable, although uniformly higher for ciprofloxacin. Colistin resistance rates were initially quite low, rose substantially, and then began to decrease at the end of the study. Clinically relevant AME genes were identified in 14% of isolates, and mutations predicted to cause resistance were relatively common in the mexZ and armZ genes. In a regression analysis, resistance to gentamicin was associated with the presence of at least one gentamicin-active AME gene and significant mutations in mexZ, parS, and fusA1. Resistance to tobramycin was associated with the presence of at least one tobramycin-active AME gene. An extensively drug-resistant strain, PS1871, was examined further and found to contain five AME genes, most of which were within clusters of antibiotic resistance genes embedded in transposable elements. These findings demonstrate the relative contributions of aminoglycoside resistance determinants to P. aeruginosa susceptibilities at a United States medical center. IMPORTANCE Pseudomonas aeruginosa is frequently resistant to multiple antibiotics, including aminoglycosides. The rates of resistance to aminoglycosides in bloodstream isolates collected over 2 decades at a United States hospital remained constant, suggesting that antibiotic stewardship programs may be effective in countering an increase in resistance. Mutations in the mexZ, fusA1, parR, pasS, and armZ genes were more common than acquisition of genes encoding aminoglycoside modifying enzymes. The whole-genome sequence of an extensively drug resistant isolate indicates that resistance mechanisms can accumulate in a single strain. Together, these results suggest that aminoglycoside resistance in P. aeruginosa remains problematic and confirm known resistance mechanisms that can be targeted for the development of novel therapeutics.

Antibiotic choice for Group B Streptococcus prophylaxis in mothers with reported penicillin allergy and associated newborn outcomes

OBJECTIVE

To evaluate the choice of antibiotic used for intrapartum Group B Streptococcus (GBS) prophylaxis in pregnant individuals with reported penicillin allergies compared to those without reported penicillin allergies and investigate whether there are associated differences in neonatal outcomes.

STUDY DESIGN

This retrospective cohort study included mother-infant dyads of GBS positive pregnant individuals who labored and delivered newborns ≥ 35 weeks of gestation at a high-volume urban hospital (2005-2018). The type of antibiotic administered to the mothers for GBS prophylaxis (beta-lactam prophylaxis defined as penicillin-class drug or cefazolin; alternative prophylaxis defined as vancomycin or clindamycin) was compared between those with a penicillin allergy documented in their medical record versus those who did not. Neonatal outcomes included number of postnatal blood draws, antibiotic administration, neonatal intensive care unit (NICU) admission, bacteremia, and hospital length of stay and were compared between groups. Bivariable and multivariable analyses were performed.

RESULTS

Of 11,334 mother-infant pairs, 1170 (10.3%) mothers had a penicillin allergy documented in their medical record. Of them, 49 (4.2%) received a penicillin, 259 (22.1%) received cefazolin, 449 (38.4%) received clindamycin, and 413 (35.3%) received vancomycin. Patients with a reported penicillin allergy were significantly more likely to receive alternative GBS prophylaxis compared to those without penicillin allergy (73.7% vs. 0.2%, p < 0.01). Neonates of patients who received alternative GBS prophylaxis were significantly more likely to undergo a postnatal lab draw compared to neonates of patients who received beta-lactam antibiotics (20.8% vs. 17.3%, OR 1.25 (95% CI 1.08-1.46)). This significant association persisted after adjusting for potential confounders (aOR 1.23, 95% CI 1.06-1.43). There were no other significant differences seen in other newborn outcomes.

CONCLUSION

Pregnant individuals who report a penicillin allergy were more likely to receive alternative antibiotics for GBS prophylaxis compared to those without a penicillin allergy. This was associated with an increased frequency of postnatal blood draws among neonates of mothers with a reported penicillin allergy. Administration of alternative intrapartum antibiotic prophylaxis with vancomycin or clindamycin is common in individuals with self-reported penicillin allergy, and maternal alternative antibiotic administration may impact neonatal care, particularly via increased lab draws.

Machine Learning To Stratify Methicillin-Resistant Staphylococcus aureus Risk among Hospitalized Patients with Community-Acquired Pneumonia

Methicillin-resistant Staphylococcus aureus (MRSA) is an uncommon but serious cause of community-acquired pneumonia (CAP). A lack of validated MRSA CAP risk factors can result in overuse of empirical broad-spectrum antibiotics. We sought to develop robust models predicting the risk of MRSA CAP using machine learning using a population-based sample of hospitalized patients with CAP admitted to either a tertiary academic center or a community teaching hospital. Data were evaluated using a machine learning approach. Cases were CAP patients with MRSA isolated from blood or respiratory cultures within 72 h of admission; controls did not have MRSA CAP. The Classification Tree Analysis algorithm was used for model development. Model predictions were evaluated in sensitivity analyses. A total of 21 of 1,823 patients (1.2%) developed MRSA within 72 h of admission. MRSA risk was higher among patients admitted to the intensive care unit (ICU) in the first 24 h who required mechanical ventilation than among ICU patients who did not require ventilatory support (odds ratio [OR], 8.3; 95% confidence interval [CI], 2.4 to 32). MRSA risk was lower among patients admitted to ward units than among those admitted to the ICU (OR, 0.21; 95% CI, 0.07 to 0.56) and lower among ICU patients without a history of antibiotic use in the last 90 days than among ICU patients with antibiotic use in the last 90 days (OR, 0.03; 95% CI, 0.002 to 0.59). The final machine learning model was highly accurate (receiver operating characteristic [ROC] area = 0.775) in training and jackknife validity analyses. We identified a relatively simple machine learning model that predicted MRSA risk in hospitalized patients with CAP within 72 h postadmission.

139. Development of cefiderocol resistance in an Enterobacter hormaechei strain following prolonged antibiotic exposure

Background

Cefiderocol (FDC) is a novel antimicrobial agent used for multi-drug resistant Gram-negative pathogens. To date, reports of mutations in β-lactamase and siderophore complex genes have been described and may contribute to FDC resistance. This case describes a New Dehli metallo-β-lactamase (NDM)-producing strain of Enterobacter hormaechei that developed FDC resistance following antibiotic exposure.

Methods

Serial respiratory and blood cultures were collected from a lung transplant recipient throughout 72 days of hospitalization. Confirmatory susceptibility and combination minimal inhibitory concentration (MIC) testing were performed using broth dilution and E-test assays. Short-read sequencing libraries were prepared using a seqWell plexWell 96 kit, and whole-genome sequencing was performed using the Illumina NovaSeq platform. Reads from the sample genomes were aligned to the chromosome and three plasmid sequences of reference genome ENCL48880.

Results

Four serial respiratory E. hormaechei isolates and one blood isolate were evaluated. Although initial isolates were susceptible to FDC (MICs 1-2 µg/mL), two respiratory isolates cultured after 41 days of FDC therapy had MICs of 128 µg/mL. The blood isolate remained FDC susceptible despite respiratory resistance. The combination of ceftazidime/avibactam and aztreonam was determined to be active via synergy MIC testing in all isolates, and aztreonam therapeutic drug monitoring confirmed an adequate dosing strategy. Whole-genome sequencing revealed no nonsynonymous single nucleotide variants (SNVs) within the chromosomes but identified a deletion of a large urease island in the resistant isolates. In four of the five isolates, a plasmid (p48880_mcr) was identified and analyzed for possible contributions to FDC resistance.

Enterobacter Isolate Assemblies

This figure demonstrates genomic assemblies from the five Enterobacter clinical isolates, noting an absence of sequence from ECResp2.

Conclusion

This case demonstrates development of FDC resistance in E. hormaechei isolates during a 41 day course of FDC therapy. Possible causes of resistance include a large chromosomal deletion and plasmid alleles, demonstrating a potential novel mechanism for FDC resistance. Partnering molecular testing and enhanced antimicrobial stewardship should be encouraged to optimize selection of regimens and durations to prevent resistance to FDC.

Disclosures

Michael G. Ison, MD MS, GlaxoSmithKlein: Grant/Research Support|Pulmocide: Grant/Research Support|Viracor Eurfins: Advisor/Consultant Nathaniel J. Rhodes, PharmD, MSc, American Academy of Colleges of Pharmacy: Grant/Research Support|Paratek: Grant/Research Support|Third Pole Therapeutics: Advisor/Consultant.

598. Area under the curve-guided vancomycin monitoring and risk of nephrotoxicity in non-Staphylococcus aureus infections: A case-control study

Background

Area under the curve (AUC)-guided monitoring of vancomycin for the treatment of Staphylococcus aureus (SA) infections demonstrates reduced rates of nephrotoxicity in clinical studies. Many institutions utilize AUC-guided dosing for all patients receiving vancomycin, despite extrapolated AUC goals for non-SA infections. We sought to define risk factors for vancomycin-induced kidney injury (VIKI) in non-SA infections.

Methods

This was a retrospective, single-center, case-control study evaluating risk factors associated with VIKI in hospitalized patients receiving AUC-guided dosing for non-SA infections from 2/2019-10/2021. Cases were defined as patients with non-SA infections who received >72 hours of vancomycin and had >1 observed vancomycin concentration with a corresponding AUC calculated who developed VIKI within 24 hours of vancomycin discontinuation. Controls had to meet all case criteria but did not have VIKI. Univariate and multivariable analyses were used to identify risk factors associated with VIKI. Multivariable analyses were conducted using the Optimal Data Analysis package for R.

Results

Twenty-three cases and 48 controls were included. Leading indications were bloodstream (52.1%) and severe skin/skin structure (46.5%) infections. Isolated pathogens from culture included coagulase-negative Staphylococcus (49.3%) and Streptococcus spp. (43.7%). The majority of vancomycin AUCs (52%) were collected within 24-48 hours of initiation. The median first and second AUCs were higher in cases vs. controls [429 vs. 385 mg*hr/L, p=0.013; and 573 vs. 429 mg*hr/L, p=0.021], respectively. Most patients (75%) experienced AKI within 72 hours of vancomycin initiation, with a median time to AKI of 5 days (IQR 2.5-7). Risk factors associated with AKI included any AUC exceeding 515 mg*hr/L, infection caused by pathogens other than Streptococcus spp., and non-bacteremia indications. Patients with AUCs exceeding 515 mg*hr/L had 3.7-fold greater odds of VIKI (p=0.017).

Conclusion

We found that higher AUCs increased the risk of VIKI in non-SA infections and that the risk of VIKI varied by vancomycin indication. Our findings agree with previous studies in SA indicating that vancomycin AUC should not generally exceed 515 mg*hr/L.

Disclosures

Nathaniel J. Rhodes, PharmD MS, Paratek: Grant/Research Support|Third Pole Therapeutics: Advisor/Consultant.

967. Safety Outcomes of a Hospital-wide β-Lactam Graded Challenge Allergy Protocol

Background

Up to 15% of hospitalized patients report a penicillin allergy, but most can tolerate a β-lactam (BL). Use of second-line non-BL antibiotics poses untoward health consequences. Assessing for true penicillin allergies includes penicillin skin testing (PST) and a direct amoxicillin challenge, each with their own limitations in hospitalized patients. For inpatients, a graded challenge (GC) with the desired BL offers a streamlined approach for many who could benefit from a first-line BL agent. In 2019, a hospital-wide BL Allergy Assessment and Clinical Pathway was implemented, including a BL GC protocol for low-risk patients. This study aimed to assess the safety of the GC procedure in hospitalized patients.

Methods

A retrospective, observational cohort study of adult inpatients who completed a GC procedure between Sept 2019 – Sept 2021 was conducted. Primary objective: determine the incidence of a significant hypersensitivity reaction from a BL GC. Secondary objectives: 1) determine the incidence of a non-hypersensitivity reaction and 2) identify antimicrobial stewardship interventions in those tolerant to a BL GC (e.g. antibiotic switch to a BL with completion of treatment course and de-labeling of penicillin allergy).

Results

Fifty-one patients completed a GC procedure. Most (78%) had a reported allergy to penicillin vs. other BL antibiotics. Reported allergic reactions stratified by risk for a serious hypersensitivity episode were: low/reaction &gt; 10 yrs ago – 33%; moderate-high/reaction &gt; 10 yrs ago – 47%, and moderate-high/reaction &lt; 5 yrs ago – 19.6%. A PST prior to a GC was performed in 75% of patients. Common GC agents included amoxicillin-clavulanate (16%), amoxicillin (12%) and ceftriaxone (12%). One patient experienced a hypersensitivity reaction managed with diphenhydramine and another patient had a non-hypersensitivity reaction. Both cases were non-life-threatening. Of the 49 patients who tolerated a GC, 76% were switched to a BL with completion of treatment course, and 84% of documented penicillin allergies were de-labeled or clarified in the electronic medical record.

Conclusion

The GC procedure in our hospitalized patients was generally well tolerated including those with an allergy history concerning for a moderate-high risk hypersensitivity reaction.

Disclosures

Nathaniel J. Rhodes, PharmD, MSc, American Academy of Colleges of Pharmacy: Grant/Research Support|Paratek: Grant/Research Support|Third Pole Therapeutics: Advisor/Consultant Marc H. Scheetz, PharmD, MSc, Abbvie: Advisor/Consultant|Allecra: Grant/Research Support|Merck: Advisor/Consultant|Nevakar: Advisor/Consultant|Nevakar: Grant/Research Support|Premier Healthcare Solutions: Honoraria|Spero: Advisor/Consultant|SuperTrans Medical: Advisor/Consultant|SuperTrans Medical: Grant/Research Support|Takeda: Advisor/Consultant|Third Pole Therapeutics: Advisor/Consultant.

Individual target pharmacokinetic/pharmacodynamic attainment rates among meropenem-treated patients admitted to the ICU with hospital-acquired pneumonia

OBJECTIVES

Critical illness reduces β-lactam pharmacokinetic/pharmacodynamic (PK/PD) attainment. We sought to quantify PK/PD attainment in patients with hospital-acquired pneumonia.

METHODS

Meropenem plasma PK data (n = 70 patients) were modelled, PK/PD attainment rates were calculated for empirical and definitive targets, and between-patient variability was quantified [as a coefficient of variation (CV%)].

RESULTS

Attainment of 100% T&gt;4×MIC was variable for both empirical (CV% = 92) and directed (CV% = 33%) treatment.

CONCLUSIONS

Individualization is required to achieve suggested PK/PD targets in critically ill patients.

Role of Therapeutic Drug Monitoring in the Treatment of Persistent Mycobacterium abscessus Central Nervous System Infection: A Case Report and Review of the Literature

A patient presenting with recurrent ventriculoperitoneal shunt infection was found to have Mycobacterium abscessus growing from cerebrospinal fluid (CSF), which remained persistently positive. Therapeutic monitoring of clarithromycin, imipenem, and linezolid in CSF and plasma revealed lower than expected concentrations, prompting alternative therapy and culture clearance on hospital day 42.

Urinary Metabolomics from a Dose-Fractionated Polymyxin B Rat Model of Acute Kidney Injury

BACKGROUND

Polymyxin B treatment is limited by kidney injury. We sought to identify Polymyxin B related urinary metabolomic profile modifications for early detection of polymyxin-associated nephrotoxicity.

METHODS

Samples were obtained from a previously conducted study. Male Sprague-Dawley rats received dose-fractionated polymyxin B (12mg/kg/day) once daily (QD), twice daily (BID), and thrice daily (TID) for three days with urinary biomarkers and kidney histopathology scores determined. Daily urine was analysed for metabolites via 1H NMR. Principal Components Analyses identified spectral data trends with orthogonal Partial Least Square Discriminant Analysis applied to classify metabolic differences. Metabolomes were compared across groups (i.e., those receiving QD, BID, TID, and control) using a mixed-effects models. Spearman correlation was performed for injury biomarkers and the metabolome.

RESULTS

A total of 25 rats were treated with Polymyxin B, and n=2 received saline, contributing 77 urinary samples. Pre-dosing samples clustered well, characterized by higher amounts of citrate, 2-oxoglutarate, and hippurate. Day 1 samples showed higher taurine; day 3 samples had higher lactate, acetate, and creatine. Taurine was the only metabolite significantly increased in both BID and TID compared to QD group. Day 1 taurine correlated with increasing histopathology scores (rho=0.4167, P=0.038) and KIM-1 (rho =0.4052, P=0.036); whereas KIM-1 on day one and day 3 did not reach significance with histopathology (rho=0.3248, P=0.11 and rho=0.3739, P=0.066).

CONCLUSIONS

Polymyxin B causes increased amounts of urinary taurine on day 1 which then normalizes to baseline concentrations. Taurine may provide one of the earlier signals of acute kidney damage caused by polymyxin B.

Pharmacokinetic/Pharmacodynamic Considerations of Alternate Dosing Strategies of Tocilizumab in COVID-19

Tocilizumab is one of few treatments that have been shown to improve mortality in patients with coronavirus disease 2019 (COVID-19), but increased demand has led to relative global shortages. Recently, it has been suggested that lower doses, or fixed doses, of tocilizumab could be a potential solution to conserve the limited global supply while conferring equivalent therapeutic benefit to the dosing regimens studied in major trials. The relationship between tocilizumab dose, exposure, and response in COVID-19 has not been adequately characterized. There are a number of pharmacokinetic (PK) parameters that likely differ between patients with severe COVID-19 and patients in whom tocilizumab was studied during the US FDA approval process. Likewise, it is unclear whether a threshold exposure is necessary for tocilizumab efficacy. The safety and efficacy of fixed versus weight-based dosing of tocilizumab has been evaluated outside of COVID-19, but it is uncertain if these observations are generalizable to severe or critical COVID-19. In the current review, we consider the potential advantages and limitations of alternative tocilizumab dosing strategies. Leveraging PK models and simulation analyses, we demonstrate that a fixed single dose of tocilizumab 400 mg is unlikely to produce PK exposures equivalent to those achieved in the REMAP-CAP trial, although weight-stratified dosing appears to produce more uniform exposure distribution. Data from current and future trials could provide PK/pharmacodynamic insight to better inform dosing strategies at the bedside. Ultimately, rational dosing strategies that balance available limited supply with patient needs are required.

Defining the Importance of Age-Related Changes in Drug Clearance to Optimizing Aminoglycoside Dosing Regimens for Adult Patients with Cystic Fibrosis

BACKGROUND AND OBJECTIVE

The number of adults living with cystic fibrosis (CF) has increased and will continue to do so with the approval of cystic fibrosis transmembrane conductance regulator (CFTR) modulators. Because systemic aminoglycosides are commonly administered for CF pulmonary exacerbations, we sought to define optimized dosing regimens using a population pharmacokinetic modeling and simulation approach.

METHODS

Adult CF patients admitted for pulmonary exacerbation, receiving at least 72 h of systemic gentamicin, tobramycin, or amikacin, with measured concentrations were included. Covariates [e.g., age, weight, creatinine clearance (CRCL)] were screened. Population modeling was completed using Monolix, and simulations were conducted in R. Simulated exposures were calculated using noncompartmental analysis. Once-daily fixed (10 mg/kg) and exposure-matched dosing (i.e., 15, 10, 7.5, 6 mg/kg for ages 20, 30, 40, and 50 years, respectively) strategies were compared. First-24 h exposures were evaluated for each strategy according to the probability of target attainment (PTA) (ratio of peak plasma concentrations relative to the minimum inhibitory concentration [C_max/MIC] or ratio of the area under the concentration-time curve to MIC [AUC/MIC]) and the probability of toxic exposure (PTE) (trough concentration, C_trough > 2 mg/l).

RESULTS

Forty-eight adult patients (55% female) were included. A one-compartment model best fit the data. Estimates for volume of distribution (V) and clearance (CL) were 22 l and 5.57 l/h, respectively. Weight significantly modified CL and V. Age significantly modified CL and was more influential than CRCL. PTA was > 90% at MICs ≤ 1 mg/l for fixed doses of 10 mg/kg and for exposure-matched doses at MIC ≤ 1 mg/l. Exposure-matched dosing reduced PTE roughly 50% in patients aged 40 and 50 years vs. fixed dosing.

CONCLUSIONS

Exposure-matching maintained PTA at MICs ≤ 1 mg/l while reducing toxicity risk in older patients compared to fixed dosing. Confirmatory studies are needed.

Impact of early antimicrobial stewardship intervention in patients with positive blood cultures: results from a randomized comparative study: Impact of stewardship on BSI outcomes

BACKGROUND

Antimicrobial stewardship intervention (ASI) appears necessary to realize the full benefits of rapid diagnostic technologies in clinical practice. This study aimed to compare clinical outcomes between early ASI paired with MALDI-TOF compared to MALDI-TOF with standard of care (SOC) reporting in patients with positive blood cultures.

METHODS

Adult patients with positive blood cultures and organism speciation via MALDI-TOF admitted between 2/2015 and 9/2015 were randomized to ASI or SOC in a 1:1 fashion. Patients admitted for at least 48 hours following positive culture were included in analyses. ASI was defined as a clinical assessment by a stewardship team member with non-binding treatment recommendations offered to the primary team. The primary outcome was time to definitive therapy. Secondary outcomes included post-culture length of stay (LOS), time to first change in antibiotics, and in-hospital mortality.

RESULTS

A total of 149 patients were included in analyses (76 in the ASI group and 73 in the SOC group). ASI and SOC arms did not differ according to age, sex, comorbidities, or severity of illness. Gram-positive organisms were common in both SOC and ASI arms (74.0 vs 61.8%, p=0.11). Time-to-definitive therapy was reduced, on average, by 30.3 hours in the ASI group (71.6 vs. 41.3 hours, p=0.01). Hospital LOS following the first positive blood culture was significantly shorter in the ASI group (8.7 vs. 11.2 days, p=0.049).

CONCLUSIONS

ASI combined with MALDI-TOF reduced the time to definitive therapy, time to first change in antibiotics, and was associated with a shorter post-culture LOS.

Implementation of a clinical pharmacist-driven comprehensive medication management program in an outpatient wound healing center

BACKGROUND

The role of the pharmacist in wound healing management among patients with diabetic and nondiabetic foot ulcers (DFU) is unclear. We sought to implement and evaluate an integrated pharmacist-driven comprehensive medication management (CMM) program in a multidisciplinary podiatrist-led wound healing center (WHC).

OBJECTIVES

The objectives were to determine the role of the clinical pharmacist in a WHC and evaluate the impact of CMM interventions on prescribing rates and wound healing rates.

METHODS

A pharmacist-driven CMM program was implemented in a podiatrist-led WHC, and an evaluation spanning 6 years was conducted.

RESULTS

Overall, 1018 patients were treated over 6 years, and 515 received wound treatment after the CMM period, of which, 309 received CMM services. A total of 441 medication related problems (MRPs) were identified; most were related to medication safety (35.1%) and inappropriate or ineffective therapy (31.3%), and problems with adherence accounted for 22.5% of documented MRPs. An average of 3.41 interventions per patient were documented, and most were related to patient education (40.8%). Only metformin (20.3 vs. 34.2%; P < 0.001) and insulin prescription (57.3 vs. 73.8%; P < 0.001) prevalence increased after CMM implementation. Other prescriptions were not significantly different among patients presenting in the pre- and post-CMM periods, respectively. Wound healing rates among patients with DFU were similar before and after implementation (55 vs. 52%; P = 0.49). Likewise, wound healing rates among those with non-DFUs were similar before- and after implementation (56 vs. 53%; P = 0.56).

CONCLUSION

The implementation of a novel pharmacist-driven CMM program embedded within a multidisciplinary podiatrist-managed WHC provided the initial evidence of the potential benefits of providing pharmacist-driven CMM services to patients with lower extremity ulcers. Prospective studies of CMM in this patient population are needed.

Lack of synergistic nephrotoxicity between vancomycin and piperacillin/tazobactam in a rat model and a confirmatory cellular model

BACKGROUND

Vancomycin and piperacillin/tazobactam are reported in clinical studies to increase acute kidney injury (AKI). However, no clinical study has demonstrated synergistic toxicity, only that serum creatinine increases.

OBJECTIVES

To clarify the potential for synergistic toxicity between vancomycin, piperacillin/tazobactam and vancomycin + piperacillin/tazobactam treatments by quantifying kidney injury in a translational rat model of AKI and using cell studies.

METHODS

(i) Male Sprague-Dawley rats (n = 32) received saline, vancomycin 150 mg/kg/day intravenously, piperacillin/tazobactam 1400 mg/kg/day intraperitoneally or vancomycin + piperacillin/tazobactam for 3 days. Urinary biomarkers and histopathology were analysed. (ii) Cellular injury was assessed in NRK-52E cells using alamarBlue®.

RESULTS

Urinary output increased from Day -1 to Day 1 with vancomycin but only after Day 2 for vancomycin + piperacillin/tazobactam-treated rats. Plasma creatinine was elevated from baseline with vancomycin by Day 2 and only by Day 4 for vancomycin + piperacillin/tazobactam. Urinary KIM-1 and clusterin were increased with vancomycin from Day 1 versus controls (P < 0.001) and only on Day 3 with vancomycin + piperacillin/tazobactam (P < 0.001, KIM-1; P < 0.05, clusterin). The histopathology injury score was elevated only in the vancomycin group when compared with piperacillin/tazobactam as a control (P = 0.04) and generally not so with vancomycin + piperacillin/tazobactam. In NRK-52E cells, vancomycin induced cell death with high doses (IC50 48.76 mg/mL) but piperacillin/tazobactam did not, and vancomycin + piperacillin/tazobactam was similar to vancomycin.

CONCLUSIONS

All groups treated with vancomycin demonstrated AKI; however, vancomycin + piperacillin/tazobactam was not worse than vancomycin. Histopathology suggested that piperacillin/tazobactam did not worsen vancomycin-induced AKI and may even be protective.

β-Lactam pharmacodynamics in Gram-negative bloodstream infections in the critically ill

OBJECTIVES

To determine the β-lactam exposure associated with positive clinical outcomes for Gram-negative blood stream infection (BSI) in critically ill patients.

PATIENTS AND METHODS

Pooled data of critically ill patients with mono-microbial Gram-negative BSI treated with β-lactams were collected from two databases. Free minimum concentrations (fCmin) of aztreonam, cefepime, ceftazidime, ceftriaxone, piperacillin (co-administered with tazobactam) and meropenem were interpreted in relation to the measured MIC for targeted bacteria (fCmin/MIC). A positive clinical outcome was defined as completion of the treatment course or de-escalation, without other change of antibiotic therapy, and with no additional antibiotics commenced within 48 h of cessation. Drug exposure breakpoints associated with positive clinical outcome were determined by classification and regression tree (CART) analysis.

RESULTS

Data from 98 patients were included. Meropenem (46.9%) and piperacillin/tazobactam (36.7%) were the most commonly prescribed antibiotics. The most common pathogens were Escherichia coli (28.6%), Pseudomonas aeruginosa (19.4%) and Klebsiella pneumoniae (13.3%). In all patients, 87.8% and 71.4% achieved fCmin/MIC ≥1 and fCmin/MIC >5, respectively. Seventy-eight patients (79.6%) achieved positive clinical outcome. Two drug exposure breakpoints were identified: fCmin/MIC >1.3 for all β-lactams (predicted difference in positive outcome 84.5% versus 15.5%, P < 0.05) and fCmin/MIC >4.95 for meropenem, aztreonam or ceftriaxone (predicted difference in positive outcome 97.7% versus 2.3%, P < 0.05).

CONCLUSIONS

A β-lactam fCmin/MIC >1.3 was a significant predictor of a positive clinical outcome in critically ill patients with Gram-negative BSI and could be considered an antibiotic dosing target.

Augmented renal clearance of aminoglycosides using population-based pharmacokinetic modelling with Bayesian estimation in the paediatric ICU

OBJECTIVE

To evaluate augmented renal clearance (ARC) using aminoglycoside clearance (CLAMINO24h) derived from pharmacokinetic (PK) modelling.

METHODS

A retrospective study at two paediatric hospitals of patients who received tobramycin or gentamicin from 1999 to 2016 was conducted. Compartmental PK models were constructed using the Pmetrics package, and Bayesian posteriors were used to estimate CLAMINO24h. ARC was defined as a CLAMINO24h of ≥130 mL/min/1.73 m2. Risk factors for ARC were identified using multivariate logistic regression.

RESULTS

The final population model was fitted to 275 aminoglycoside serum concentrations. Overall clearance (L/h) was=CL0×(TBW/70)0.75×AGEH/(TMH + AGEH) + CL1 (0.5/SCr), where TBW is total body weight, H is the Hill coefficient, TM is a maturation term and SCr is serum creatinine. Median CLAMINO24h in those with versus without ARC was 157.36 and 93.42 mL/min/1.73 m2, respectively (P<0.001). ARC was identified in 19.5% of 118 patients. For patients with ARC, median baseline SCr was lower than for those without ARC (0.38 versus 0.41 mg/dL, P=0.073). Risk factors for ARC included sepsis [adjusted OR (aOR) 3.77, 95% CI 1.01-14.07, P=0.048], increasing age (aOR 1.11, 95% CI 1-1.23, P=0.04) and low log-transformed SCr (aOR 0.16, 95% CI 0.05-0.52, P=0.002). Median 24 h AUC (AUC24h) was significantly lower in patients with ARC at 45.27 versus 56.95 mg·h/L, P<0.01.

CONCLUSIONS

ARC was observed in one of every five patients. Sepsis, increasing age and low SCr were associated with ARC. Increased clearance was associated with an attenuation of AUC24h in this population. Future studies are needed to define optimal dosing in paediatric patients with ARC.

Multicenter point prevalence evaluation of the utilization and safety of drug therapies for COVID-19 at the onset of the pandemic timeline in the United States

KEY POINTS

In a multicenter point-prevalence study, we found that the rate of supportive care was high; among those receiving COVID-19 drug therapies, adverse reactions occurred in 12% of patients.

PURPOSE

There are currently no FDA-approved medications for the treatment of coronavirus disease 2019 (COVID-19). At the onset of the pandemic, off-label medication use was supported by limited or no clinical data. We sought to characterize experimental COVID-19 therapies and identify safety signals during this period.

METHODS

We conducted a noninterventional, multicenter, point prevalence study of patients hospitalized with suspected/confirmed COVID-19. Clinical and treatment characteristics within a 24-hour window were evaluated in a random sample of up to 30 patients per site. The primary objective was to describe COVID-19-targeted therapies. The secondary objective was to describe adverse drug reactions (ADRs).

RESULTS

A total of 352 patients treated for COVID-19 at 15 US hospitals From April 18 to May 8, 2020, were included in the study. Most patients were treated at academic medical centers (53.4%) or community hospitals (42.6%). Sixty-seven patients (19%) were receiving drug therapy in addition to supportive care. Drug therapies used included hydroxychloroquine (69%), remdesivir (10%), and interleukin-6 antagonists (9%). Five patients (7.5%) were receiving combination therapy. The rate of use of COVID-19-directed drug therapy was higher in patients with vs patients without a history of asthma (14.9% vs 7%, P = 0.037) and in patients enrolled in clinical trials (26.9% vs 3.2%, P < 0.001). Among those receiving drug therapy, 8 patients (12%) experienced an ADR, and ADRs were recognized at a higher rate in patients enrolled in clinical trials (62.5% vs 22%; odds ratio, 5.9; P = 0.028).

CONCLUSION

While we observed high rates of supportive care for patients with COVID-19, we also found that ADRs were common among patients receiving drug therapy, including those enrolled in clinical trials. Comprehensive systems are needed to identify and mitigate ADRs associated with experimental COVID-19 treatments.

803. Risk factors associated with Clostridioides difficile infection in hospitalized patients with community-acquired pneumonia

Background

Patients with community-acquired pneumonia (CAP) who are hospitalized and treated with antibiotics may carry an increased risk for developing Clostridioides difficile infection (CDI). Accurate risk estimation tools are needed to guide monitoring and CDI mitigation efforts. We aimed to identify patient-specific risk factors associated with CDI among hospitalized patients with CAP.

Methods

Design: retrospective case-control study of hospitalized patients who received CAP-directed antibiotic therapy between 1/1/2014 and 5/29/2018. Cases were hospitalized CAP patients who developed CDI post-admission. Control patients did not develop CDI and were selected at random from CAP patients hospitalized during this period. Variables: comorbidities, laboratory results, vital signs, severity of illness, prior hospitalization, and past antibiotic use. Propensity-score weights: identified via structural decomposition analysis of pre-treatment variables. Analysis: weighted classification tree models that predicted any CDI, hospital-onset CDI, and any healthcare-associated CDI according to CAP antibiotic treatment. Performance: percent accuracy in classification (PAC) and weighted positive (PPV) and negative predictive values (NPV). Modeling: completed using the ODA package (v1.0.1.3) for R (v3.5.1).

Results

A total of 32 cases and 232 controls were identified. Sixty pre-treatment variables were screened. Structural decomposition analysis, completed in two stages, identified prior hospitalization (OR 6.56, 95% CI: 3.01-14.31; PAC: 80.3%) and BUN greater than 29 mg/dL (OR 11.67, 95% CI: 2.41-56.5; PAC: 80.8%) as propensity-score weights. With respect to CDI, receipt of broad-spectrum anti-pseudomonal antibiotics was significantly (all P’s< 0.05) associated with any CDI (NPV: 90.29%, PPV: 27.94%), hospital-onset CDI (NPV: 97.53%, PPV: 26.86%), and healthcare-associated CDI (NPV: 92.89%, PPV: 27.94%).

Conclusion

We identified risk factors available at hospital admission and empiric use of broad-spectrum Gram-negative antibiotics as being associated with the development of CDI. Model PPVs were over two-fold greater than our sample base rate. Increased monitoring and avoidance of overly broad antibiotic use in high-risk patients appears warranted.

Disclosures

All Authors: No reported disclosures

Vancomycin Exposure and Acute Kidney Injury Outcome: A Snapshot From the CAMERA2 Study

Among patients with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia from a prospective randomized clinical trial, acute kidney injury (AKI) rates increased with increasing vancomycin exposure, even within the therapeutic range. AKI was independently more common for the (flu)cloxacillin group. Day 2 vancomycin AUC ≥470 mg·h/L was significantly associated with AKI, independent of (flu)cloxacillin receipt.

Multidrug resistant Aeromonas infection following medical leech therapy: A case report and development of a joint antimicrobial stewardship and infection prevention protocol

OBJECTIVE

Aeromonas sp. infections are a recognized complication of medical leech therapy (MLT). In patients requiring MLT, ciprofloxacin or trimethoprim-sulphamethoxazole are commonly used to prevent such nosocomial infections. After a patient at our institution developed a MLT-associated multi-drug resistant (MDR) Aeromonas infection, we developed and evaluated a joint antimicrobial stewardship and infection prevention protocol for MLT at our institution.

METHODS

We describe a case of a surgical site infection with MDR Aeromonas following MLT that was resistant to typically prescribed prophylactic antimicrobials, and development of a new leech culture protocol to proactively monitor for antimicrobial resistance among our institution's leech supply. We also report the rates of MLT-associated infections prior to and following implementation of this protocol and the antimicrobial susceptibility profiles detected in leech culture at our institution.

RESULTS

Between October 2014 and February 2018, 46 patients received MLT at our institution. Other than the case described in this report, no other instances of MLT-related infections were noted during this time period. Culture results from 22 leeches in six batches since February 2018 showed that all were susceptible to ciprofloxacin, TMP-SMX, and ceftriaxone. Since initiation of a leech culture protocol, no further cases of MLT-associated infections have been reported at our institution.

CONCLUSIONS

In light of increasing antimicrobial resistance and the potentially devastating consequences of MLT-associated infections, institutions offering MLT should be aware of these risks and ensure that protocols are in place to minimize infection risks for patients.

Effects of Advanced Pharmacy Practice Experience Characteristics on Postgraduate Year 1 Residency Match Rates

BACKGROUND

Mentors often provide advice to students regarding selection of Advanced Pharmacy Practice Experience (APPE) rotations to strengthen their candidacy for a residency position. However, the impact of APPE characteristics on the chances of matching is unknown.

OBJECTIVE

To determine the impact of APPE characteristics on Post Graduate Year-1 (PGY1) residency match rates at a Midwest US college of pharmacy.

METHODS

Graduates from a single college of pharmacy who participated in the PGY1 match in 2015 or 2016 were included. Match data were obtained from National Matching Services. APPE characteristics (e.g., rotation timing relative to the Midyear Clinical Meeting [MCM], rotation type, and setting) were stratified by matched status. Independent predictors were identified using multivariate logistic regression and tree-based models.

RESULTS

Ninety-nine students were included with 57 matching (57.6%). Students completing an infectious diseases rotation (75 vs. 51%; p = 0.028), a hospital rotation before the MCM (67 vs. 47%; p = 0.039), or a rotation in an ambulatory care clinic (67 vs. 47%; p = 0.045) were more likely to match. Students completing an independent community pharmacy rotation were less likely to match (8.3 vs. 64%; p < 0.001). After multivariate adjustment, all of these factors were associated with the likelihood of matching except completion of an infectious diseases (p = 0.077) or ambulatory care rotation (p = 0.073).

CONCLUSION

A hospital rotation prior to the MCM was positively associated with matching while completion of an independent community pharmacy rotation was associated with non-matched status. The utility of these findings in guiding APPE selections for students pursing residency should be explored.

Exploring the Relationship between FEV1 Loss and Recovery and Aminoglycoside Pharmacokinetics in Adult Patients with Cystic Fibrosis: Implications for Clinical Dosing Strategies

OBJECTIVE

Systemic aminoglycosides remain a cornerstone of treatment for cystic fibrosis (CF) pulmonary exacerbations (PEx); however, the impact of aminoglycoside pharmacokinetics (PK) on outcomes is not well defined in adult CF patients. Our objective was to assess the impact of increasing PK exposures on the clinical outcomes of PEx treatment in adult CF patients receiving high-dose and standard-dose extended-interval aminoglycosides.

METHODS

We conducted a retrospective study of adult CF patients treated with an intravenous aminoglycoside for a PEx. Serum amikacin, gentamicin, and tobramycin levels and forced expiratory volume over 1 second (FEV₁ ) data were used to evaluate exposure-response relationships. PK parameters were estimated using a Bayesian approach to obtain area under the curve (AUC)_{0-24 hr} , maximum concentration (C_{max0-24 hr} ), and minimum concentration (Cmin_{0-24 hr} ) estimates. The primary efficacy end point was a 90% recovery of baseline FEV₁ by 30 days posttreatment. Toxicity included signs or symptoms of ototoxicity, vestibular toxicity, or renal toxicity. Multivariate linear mixed-effects models of FEV₁ were used for exposure-response analysis.

RESULTS

The study included 51 patients who contributed 188 FEV₁ observations. There were 3.0 ± 1.7 (mean ± SD) aminoglycoside concentrations per patient. The mean AUC_{0-24 hr} , C_{max0-24 hr} , and C_{min0-24 hr} across all agents and patients were 156 ± 96 mg*hr/L, 29.9 ± 12.7 mg/L, and 0.35 ± 0.66 mg/L, respectively. A total of 42 amikacin-, gentamicin-, or tobramycin-treated patients contributed to the efficacy analysis, of whom 85.7% experienced recovery posttreatment. Of the 51 included patients, 6 (11.8%) experienced seven toxicity events. In exploratory exposure-response analyses, neither AUC_{0-24 hr} nor C_{max0-24 hr} was associated with FEV₁ values after adjusting for clinical covariates and baseline FEV₁ .

CONCLUSIONS

Increasing aminoglycoside AUC_{0-24 hr} and C_{max0-24 hr} were not associated with FEV₁ during PEx treatment. Although individualizing aminoglycoside dosing in adult CF patients is necessary to minimize toxicity risk, more work is needed to define optimally safe and effective dosing strategies for this population.

Vancomycin-Induced Kidney Injury: Animal Models of Toxicodynamics, Mechanisms of Injury, Human Translation, and Potential Strategies for Prevention

Vancomycin is a recommended therapy in multiple national guidelines. Despite the common use, there is a poor understanding of the mechanistic drivers and potential modifiers of vancomycin-mediated kidney injury. In this review, historic and contemporary rates of vancomycin-induced kidney injury (VIKI) are described, and toxicodynamic models and mechanisms of toxicity from preclinical studies are reviewed. Aside from known clinical covariates that worsen VIKI, preclinical models have demonstrated that various factors impact VIKI, including dose, route of administration, and thresholds for pharmacokinetic parameters. The degree of acute kidney injury (AKI) is greatest with the intravenous route and higher doses that produce larger maximal concentrations and areas under the concentration curve. Troughs (i.e., minimum concentrations) have less of an impact. Mechanistically, preclinical studies have identified that VIKI is a result of drug accumulation in proximal tubule cells, which triggers cellular oxidative stress and apoptosis. Yet, there are several gaps in the knowledge that may represent viable targets to make vancomycin therapy less toxic. Potential strategies include prolonging infusions and lowering maximal concentrations, administration of antioxidants, administering agents that decrease cellular accumulation, and reformulating vancomycin to alter the renal clearance mechanism. Based on preclinical models and mechanisms of toxicity, we propose potential strategies to lessen VIKI.

Evaluation of Dose-Fractionated Polymyxin B on Acute Kidney Injury Using a Translational In Vivo Rat Model

We investigated dose-fractionated polymyxin B (PB) on acute kidney injury (AKI). PB at 12 mg of drug/kg of body weight per day (once, twice, and thrice daily) was administered in rats over 72 h. The thrice-daily group demonstrated the highest KIM-1 increase (P = 0.018) versus that of the controls (P = 0.99) and histopathological damage (P = 0.013). A three-compartment model best described the data (bias, 0.129 mg/liter; imprecision, 0.729 mg2/liter2; R2, 0.652,). Area under the concentration-time curve at 24 h (AUC24) values were similar (P = 0.87). The thrice-daily dosing scheme resulted in the most PB-associated AKI in a rat model.

Piperacillin-Tazobactam Added to Vancomycin Increases Risk for Acute Kidney Injury: Fact or Fiction?

Vancomycin and piperacillin-tazobactam are 2 of the most commonly prescribed antibiotics in hospitals. Recent data from multiple meta-analyses suggest that the combination increases the risk for vancomycin-induced kidney injury when compared to alternative viable options. However, these studies are unable to prove biologic plausibility and causality as randomized controlled trials have not been performed. Furthermore, these studies define acute kidney injury according to thresholds of serum creatinine rise. Serum creatinine is not a direct indicator of renal injury, rather a surrogate of glomerular function. More reliable, specific, and sensitive biomarkers are needed to truly define if there is a causal relationship with increased toxicity when piperacillin-tazobactam is added to vancomycin. This viewpoint will explore the available evidence for and against increased acute kidney injury in the setting of vancomycin and piperacillin-tazobactam coadministration.

Assessment of mortality stratified by meropenem minimum inhibitory concentration in patients with Enterobacteriaceae bacteraemia: A patient-level analysis of published data

In 2010, the Clinical and Laboratory Standards Institute (CLSI) lowered carbapenem breakpoints to reduce the proportion of 'susceptible' organisms that produced carbapenemases. Few studies have evaluated the effect of this change on clinical outcomes. This systematic review aimed to evaluate the effect of carbapenem MICs on 30-day mortality from pooled patient-level data from studies of patients treated with carbapenems across a range of meropenem MICs. PubMed was searched to March 2019 with the terms 'carbapenem', 'meropenem', 'imipenem', 'doripenem', 'ertapenem', 'susceptibility' and 'outcomes'. Studies were included in the analysis if patients had Enterobacteriaceae bacteraemia treated with a carbapenem for ≥48 h and mortality was reported. Studies were excluded if all isolates were either susceptible or resistant to meropenem based on CLSI 2010 breakpoints or if only carbapenemase-producing isolates were included. Authors were contacted for patient-level data. The primary outcome was 30-day mortality, with planned subset analyses of patients treated with meropenem, receiving active combination therapy, treated in the ICU or infected with Klebsiella pneumoniae. Of 157 articles identified, 4 met the inclusion criteria (115 eligible patients). The odds of mortality increased with each increasing meropenem MIC dilution (OR = 1.51, 95% CI 1.06-2.15) as a continuous variable. A similar increase in odds was observed in patients treated with meropenem, treated in the ICU, infected with K. pneumoniae or receiving no other active antimicrobials. Increasing meropenem MICs in Enterobacteriaceae were associated with increased mortality; however, more work is needed to define optimal clinical decision rules for infections within the susceptible range.

Vancomycin Area Under the Curve and Acute Kidney Injury: A Meta-analysis

BACKGROUND

This study analyzed the relationship between vancomycin area under the concentration-time curve (AUC) and acute kidney injury (AKI) reported across recent studies.

METHODS

A systematic review of PubMed, Medline, Scopus, and compiled references was conducted. We included randomized cohort and case-control studies that reported vancomycin AUCs and risk of AKI (from 1990 to 2018). The primary outcome was AKI, defined as an increase in serum creatinine of ≥0.5 mg/L or a 50% increase from baseline on ≥2 consecutive measurements. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Primary analyses compared the impact of AUC cutpoint (greater than ~650 mg × hour/L) and AKI. Additional analysis compared AUC vs trough-guided monitoring on AKI incidence.

RESULTS

Eight observational studies met inclusion/exclusion criteria with data for 2491 patients. Five studies reported first-24-hour AUCs (AUC0-24) and AKI, 2 studies reported 24- to 48-hour AUCs (AUC24-48) and AKI, and 2 studies reported AKI associated with AUC- vs trough-guided monitoring. AUC less than approximately 650 mg × hour/L was associated with decreased AKI for AUC0-24 (OR, 0.36 [95% CI, .23-.56]) as well as AUC24-48 (OR, 0.45 [95% CI, .27-.75]). AKI associated with the AUC monitoring strategy was significantly lower than trough-guided monitoring (OR, 0.68 [95% CI, .46-.99]).

CONCLUSIONS

AUCs measured in the first or second 24 hours and lower than approximately 650 mg × hour/L may result in a decreased risk of AKI. Vancomycin AUC monitoring strategy may result in less vancomycin-associated AKI. Additional investigations are warranted.

1569. A Translational Model to Assess the Impact of Polymyxin B Dose Fractionation on Kidney Injury

Background

Progression of antimicrobial resistance has revived Polymyxin B (PB) use in clinical practice. Dose-dependent acute kidney injury (AKI) limits its clinical use. It is unclear whether dose fractionation of total daily dose can lessen kidney injury. We assessed the role of PB fractionation on AKI in a translational model that employs sensitive urine biomarkers qualified by the FDA.

Methods

Male Sprague–Dawley rats received 12 mg/kg/day PB subcutaneously for 3 days or equal-volume normal saline (NS). PB was administered in 3 separate fractionated daily doses: 12 mg/kg daily (QD), 6 mg/kg twice daily (BID), and 4 mg/kg thrice daily (TID). Staggered blood sampling was done on days 1 to 4 and 24 hour urine was collected at baseline, on days 1, 2, and 3. Plasma creatinine (Cr) was quantified using LCMS/MS, and 24 hour urinary biomarkers (KIM1, OPN, CLN, calbindin, GSTα, IP-10, TIMP-1, and VEGF) were assayed with MILLIPLEX Rat Kidney Toxicity Magnetic Bead Panel. Mixed-effects models were used.

Results

A total of 32 rats contributed to the study data. Mean Cr were constant across groups over time (Figure 1, P = 0.18). For NS group, all biomarkers remained at baseline throughout study. Significant differences were seen for fractionation schemes for KIM1 (P = 0.02), CLN (P = 0.03), IP-10 (0.007) and TIMP-1 (P = 0.04). The differences for KIM1, IP-10, and TIMP-1 were driven by higher observed values in TID than those of BID as early as day 1 (P < 0.04). Furthermore, CLN was elevated for TID when compared with BID at baseline (P = 0.048). Similarly, TID group had the highest (but non-significant) elevations for IP-10 and TIMP-1 compared with QD on study days. Amongst all urine biomarkers, KIM1 in TID exhibited the most rapid rise from baseline to day 2 (Figure2, P < 0.0001).

Conclusion

In this translational model in which a single total daily dose was fractionated, sensitive urinary biomarkers indicated that TID dosing was worse than BID or QD dosing; dose fractionation of PB may lead to increased AKI. In addition, KIM1 rose rapidly as an early marker for AKI. Further efforts are needed to investigate the PK-TD relationship of PB in order to decrease AKI.

Disclosures

All authors: No reported disclosures.

1335. A Translational Nephrotoxicity Model to Probe Acute Kidney Injury with Vancomycin and Piperacillin–Tazobactam

Background

Vancomycin and piperacillin–tazobactam (VAN+TZP) are two of the most commonly utilized antibiotics in the hospital setting and are reported in clinical studies to increase acute kidney injury (AKI). However, no clinical study has demonstrated that synergistic AKI occurs, only that serum creatinine increases with VAN+TZP. Previous preclinical work demonstrated that novel urinary biomarkers and histopathologic scores were not increased in the VAN+TZP group compared with VAN alone. The purpose of this study was to assess changes in urinary output and plasma creatinine between VAN, TZP, and VAN+TZP treatments.

Methods

Male Sprague–Dawley rats (n = 32) received either saline, VAN 150 mg/kg/day intravenously, TZP 1,400 mg/kg/day intraperitoneally, or VAN+TZP for 3 days. Animals were placed in metabolic cages pre-study and on drug dosing days 1–3. Urinary output, plasma creatinine, urinary biomarkers were compared daily and kidney histopathology was compared at the end of therapy between the groups. Mixed-effects, repeated-measures models were employed to assess differences between the groups.

Results

In the VAN-treated rats, urinary output was increased on days 1, 2 and 3 compared with baseline and saline (P < 0.01 for all), whereas it increased later for VAN+TZP (i.e., day 2 and 3 compared with saline, P < 0.001). No changes in urinary output were observed with saline and TZP alone. Plasma creatinine rose for VAN on days 1, 2, and 3 from baseline and VAN+TZP on day 3 (P < 0.02 for all), but no treatment group was different from saline. In the VAN-treated rats, urinary KIM-1 and clusterin were increased on days 1, 2, and 3 compared with controls (P < 0.001). Elevations were seen only after 3 days of treatment with VAN+TZP (P < 0.001 KIM-1, P < 0.05 clusterin). No changes in urinary biomarkers output were observed with saline and TZP alone. Histopathology was only elevated in the VAN group compared with saline (P < 0.002). No histopathology changes were noted with VAN+TZP.

Conclusion

All groups with VAN demonstrated kidney injury; however, VAN+TZP did not cause more kidney injury than VAN alone in a rat model of VIKI when using plasma creatinine, urinary output, or urinary biomarkers as outcomes. Histopathology data suggest that adding TZP did not worsen VAN-induced AKI and may even be protective.

Disclosures

Kevin J. Downes, MD, Merck: Grant/Research Support, Research Grant; Pfizer: Grant/Research Support.

1548. Characterizing Cefepime Neurotoxicity: Experience from a Tertiary Care Center Performing β-lactam Therapeutic Drug Monitoring

Background

Based on prior studies, elderly patients and those with renal dysfunction are prone to cefepime (CFP) toxicity. The toxicokinetics and toxicodynamics for CFP are not well established. Lamoth et al. reported a 50% probability of CFP neurotoxicity at a serum trough concentration of ≥22 mg/L, whereas Huwyler et al. observed CFP neurotoxicity when concentrations exceeded 35 mg/L. The objectives of this study were to quantify the incidence of CFP neurotoxicity and to assess the association between CFP concentrations and neurotoxicity.

Methods

We conducted a retrospective review between March 2016 and May 2018, of adult patients with serum CFP trough concentrations ≥25 mg/L. To be considered a CFP neurotoxicity case, patients were required to fulfill at least two of the NCI criteria for neurological toxicity such as, presence of new-onset confusion, delirium, or drowsiness. Following this, cases were classified as (1) high likelihood of toxicity (HLT) if they either had a neurology consult or EEG findings consistent with CFP toxicity and if their symptoms improved after discontinuation of CFP, (2) possible toxicity (PT) if neurology consult or EEG was absent or if we were unable to assess improvement after CFP was discontinued, or (3) nontoxicity (NT). Cases were independently reviewed by an ID pharmacist and physician. Additional data such as comorbidities, renal function, and use of anti-epileptics were collected.

Results

One hundred and forty-two patients were included in the analysis. Neurotoxicity (HLT+PT) related to CFP occurred in 18/142 (13%) patients; 67% (12/18) were considered HLT. The median age in the HLT cohort was 68 years (interquartile range [IQR], 57–74), with toxicity occurring a median of 6 days (IQR, 5–8) after starting CFP. At the time of neurotoxicity, HLT patients had diminished renal function with a median SCr of 1.6 mg/dL (IQR, 1.2–2.4) and a corresponding CrCl of 35.8 mL/minute (IQR, 19.2–50.9). The median CFP trough concentration in the HLT patients was 62 mg/L (IQR, 50–73) vs. 70mg/L (IQR, 41–115) in the PT and 42 mg/L (IQR, 31–61) in the NT groups.

Conclusion

Our data emphasize the need for careful dosing in older patients with renal insufficiency. Interestingly, our study reveals higher cefepime troughs (~3-fold higher) associated with neurotoxicity than previously reported.

Disclosures

All authors: No reported disclosures.

2203. Patient-Specific Risk Stratification to Identify Patients at High and Low Risk for P. aeruginosa in Community-Acquired Pneumonia

Background

Pseudomonas aeruginosa (PsA) is an infrequent pathogen associated with poor outcomes in community-acquired pneumonia (CAP). Identifying patients at high and low-risk for PsA in CAP is necessary to reduce inappropriate and overly broad-spectrum antibiotic use. We evaluated the distribution of risk-factors in hospitalized CAP patients with and without PsA infection.

Methods

Design: retrospective, single-center, case–control study. Inclusion: hospitalized CAP patients admitted to the general medicine wards between January 1, 2014 and May 29, 2018. Exclusion: cystic fibrosis, ≥ 3 admissions within 30 days, CAP requiring ICU admission, and death within 48 hours of admission. Case patients had PsA in respiratory or blood cultures during the index CAP admission. Controls were randomly selected targeting a 3:1 ratio. Comorbidities, pneumonia severity index, and m-APACHE II were assessed. Gram-negative risk factors defined by Shindo et al. 2013 (PMID: 23855620) and validated by Kobayashi et al. (2018; PMID: 30349327) were scored for each patient. Stepwise logistic regression was used to identify covariates that distinguished cases from controls at a P < 0.2; these were then used to generate propensity weights (i.e., inverse-probability conditioned on covariates). Unadjusted and adjusted odds ratios for case status were estimated using logistic regression according to: the total number of risk factors present and threshold values, respectively. All analyses were conducted using IC Stata (v.14.2).

Results

54 cases and 152 controls were included. The distribution of the patient-specific sum of risk factors for PsA is shown in Figure 1. The univariate OR for case status was 4.29 (95% CI:1.55–11.9) at n = 3 risk factors, which was similar after propensity weight adjustment [aOR = 4.64 (95% CI: 1.32–16.3)]. The univariate OR of case status was 2.98 among patients with ≥ 3 risk factors (95% CI: 1.34–6.62), which was similar after propensity weight adjustment [aOR = 2.8 (95% CI: 1.02–7.72)], and correct classification was 73.8%.

Conclusion

At a threshold of ≥ 3 PsA risk factors, cases and controls were well classified, even after adjusting for propensity weights. The impact of patient-specific PsA risk-stratification on CAP outcomes and appropriate antibiotic use should be evaluated.

Disclosures

All authors: No reported disclosures.

2010. A Significant Reduction in Empiric Vancomycin Days of Therapy for Suspected MRSA Pneumonia in Adult Non-ICU Patients After Implementation of a Rapid MRSA Nasal PCR Test with Antimicrobial Stewardship Intervention

Background

Methicillin-resistant Staphylococcus aureus (MRSA), when implicated in respiratory tract infections, can be associated with significant morbidity and mortality. The prevalence of severe MRSA pneumonia may be as high as 10%; however, recent evidence suggests that MRSA is much less prevalent as a cause of community-acquired pneumonia (CAP) among community-dwelling patients and may be as low as 0.1%. Nonspecific features of pneumonia in non-ICU patients (viral co-infection, multi-lobar infiltrates) often lead clinicians to cautiously initiate empiric anti-MRSA therapy. Recommendations of when to safely de-escalate empiric treatment prior to known respiratory cultures are not established. To decrease anti-MRSA therapy in non-ICU pneumonia patients with a low probability of MRSA pneumonia, we employed a nasal screening paired with antimicrobial stewardship intervention.

Methods

A retrospective, single-center, pre-post interventional study was conducted at Northwestern Memorial Hospital (NMH), in Chicago, IL, to assess the duration of empiric vancomycin for suspected MRSA pneumonia in non-ICU patients before (January 2019) and after (March 2019) the implementation of a rapid MRSA nasal PCR test. During the post-implementation period, an NMH Antimicrobial Stewardship (AS) member identified and assessed the daily (M-F) use of empiric vancomycin for pneumonia in non-ICU patients. When vancomycin use criteria were not met, the AS pharmacist requested the team order a BD MRSA Nasal PCR test (NPV: 97.2%) to classify patients as either possible MRSA pneumonia or unlikely MRSA pneumonia. Results of a negative MRSA Nasal PCR with an ongoing clinical disposition not suggestive of MRSA pneumonia prompted the AS pharmacist to recommend de-escalation of vancomycin.

Results

See table.

Conclusion

The use of a rapid MRSA nasal PCR test with active antimicrobial stewardship intervention significantly reduced the duration of empiric vancomycin in hospitalized non-ICU patients with suspected MRSA pneumonia.

Disclosures

All authors: No reported disclosures.

Long-term Persistence of an Extensively Drug-Resistant Subclade of Globally Distributed Pseudomonas aeruginosa Clonal Complex 446 in an Academic Medical Center

BACKGROUND

Antimicrobial resistance (AMR) is a major challenge in the treatment of infections caused by Pseudomonas aeruginosa. Highly drug-resistant infections are disproportionally caused by a small subset of globally distributed P. aeruginosa sequence types (STs), termed "high-risk clones." We noted that clonal complex (CC) 446 (which includes STs 298 and 446) isolates were repeatedly cultured at 1 medical center and asked whether this lineage might constitute an emerging high-risk clone.

METHODS

We searched P. aeruginosa genomes from collections available from several institutions and from a public database for the presence of CC446 isolates. We determined antibacterial susceptibility using microbroth dilution and examined genome sequences to characterize the population structure of CC446 and investigate the genetic basis of AMR.

RESULTS

CC446 was globally distributed over 5 continents. CC446 isolates demonstrated high rates of AMR, with 51.9% (28/54) being multidrug-resistant (MDR) and 53.6% of these (15/28) being extensively drug-resistant (XDR). Phylogenetic analysis revealed that most MDR/XDR isolates belonged to a subclade of ST298 (designated ST298*) of which 100% (21/21) were MDR and 61.9% (13/21) were XDR. XDR ST298* was identified repeatedly and consistently at a single academic medical center from 2001 through 2017. These isolates harbored a large plasmid that carries a novel antibiotic resistance integron.

CONCLUSIONS

CC446 isolates are globally distributed with multiple occurrences of high AMR. The subclade ST298* is responsible for a prolonged epidemic (≥16 years) of XDR infections at an academic medical center. These findings indicate that CC446 is an emerging high-risk clone deserving further surveillance.

Measuring the impact of varying denominator definitions on standardized antibiotic consumption rates: implications for antimicrobial stewardship programmes

Objectives

To quantify the impact of varying the at-risk days definition on the overall report of at-risk days and on the calculated standardized consumption rates (SCRs) for piperacillin/tazobactam, amikacin, daptomycin and vancomycin.

Methods

Data were evaluated for two system hospitals, an 894 bed academic centre and a 114 bed community hospital. Aggregate inpatient antibiotic administration and occupancy data were extracted from electronic databases at the facility-wide level. Occupancy data were reported from admission-discharge-transfer systems. At-risk days were defined as hospital days present (DP), patient days (PD), persons present (PP) and billing days (BD). Inpatient antimicrobial days of therapy (DOT) across four major antimicrobial agents were used to calculate facility-wide SCRs using each denominator and were evaluated by least-squares regression and R2 values.

Results

Within the 894 bed academic hospital, the average monthly facility-wide days were 28 424, 22 198, 15 957 and 14 789 by the DP, PP, PD and BD definitions, respectively. Within the 114 bed community hospital, the average monthly facility-wide days were 5175, 3523 and 2816 by the DP, PP and PD definitions, respectively. Strong concordance was observed between facility-wide SCRs using the DP and PP definitions in both the academic (R2 = 0.99, y = 0.78x - 0.001) and community (R2 = 0.99, y = 0.68x - 0.03) centres across all four inpatient antibiotics evaluated. In an analysis of piperacillin/tazobactam SCRs, rates were over-predicted by 28%-93% at the facility-wide level across centres using alternative denominators.

Conclusions

We found that data source and definitions of at-risk denominator days meaningfully impact antibiotic SCRs. Centres should carefully consider these potential sources of variation when setting consumption benchmarks and internally evaluating use.

Discrepancies Between Patient Self-Reported and Electronic Health Record Documentation of Medication Allergies and Adverse Reactions in the Acute Care Setting: Room for Improvement

Background: Allergy information is commonly transcribed into an electronic health record (EHR) for all patients admitted to acute care hospital units by a licensed health care professional. The allergy history is utilized each time a new inpatient medication is prescribed to identify the patient's risk of having an allergic reaction and/or anaphylaxis. There is potential for negative consequences in cases where the allergy history is incorrectly documented. Objective: The objective of this study was to assess the discordance between documented allergy information in the EHR and verbally reported allergy information from a patient interview. Methods: Prospective, observational, nonrandomized study performed within a 2-month period during the Spring of 2016. The study was performed at a teaching community hospital in Chicago, Illinois. A total of 270 patients were interviewed on the general medicine (n = 216) and headache (n = 54) units regarding their medication allergies and reactions. The outcomes were discordance among EHR-documented and verbally stated medication allergies and reactions. Results: The agreement across all medications and reactions between the EHR and patient self-reported interview was 80.9%. There were 31 reactions (6.7%) that were verbally reported by patients but were not documented in the EHR (omissions) and 57 reactions (12.4%) that were verbally reported but were incorrectly documented in the EHR (incorrect documentations). Only 20 out of the 264 verbally reported reactions (7.5%) met the study definition of anaphylaxis. The highest rate of incorrect documentations occurred with opiate agonists, and the highest rate of omissions occurred with anticonvulsants. EHR documentation was more likely to be incorrect among patients who reported gastrointestinal reactions and was more likely to be correct among patients who reported cutaneous reactions. Conclusion: There was a high rate of discordance amid EHR-documented and verbally stated medication allergies and reactions. Errors among opiate agonists, anticonvulsants, and sulfa drugs were most prevalent.

1068. Evaluation of Cefazolin vs. Anti-Staphylococcal Penicillins for the Treatment of Methicillin-Susceptible Staphylococcus aureus Bloodstream Infections in Acutely-Ill Adult Patients: Results of a Systematic Review and Meta-Analysis

Background

Anti-staphylococcal penicillins (ASPs) have been regarded as first-line in the treatment of serious MSSA bloodstream infections (BSI) with cefazolin considered an alternative. Recent studies have suggested that infection outcomes between cefazolin and ASPs may be similar. The objective of this study was to compare the clinical efficacy and tolerability of cefazolin to ASPs for MSSA BSI.

Methods

A systematic review and meta-analysis was conducted. Articles were identified via PubMed, Web of Science, and the Cochrane Library. Studies written in English comparing cefazolin to ASPs for MSSA BSI in adult patients were included. Study quality was assessed using the Cochrane Risk of Bias Assessment Tool and the Newcastle-Ottawa Scale for prospective and retrospective studies, respectively. All review stages were independently conducted by two reviewers, with a third reviewer adjudicating any discrepancies. The fixed- or random-effects model was utilized, as appropriate. A planned subgroup analysis was conducted between high (>15%) vs. low (<14.9%) mortality probability as defined by logit functions applied at the study level.

Results

Nine studies were identified. Pooled data extracted from 1,726 cefazolin- and 2,716 ASP-patients indicated that cefazolin was associated with a significant reduction in treatment failure (OR: 0.70; 95% CI: 0.61–0.82; P < 0.001; I² = 14%) and crude, all-cause mortality (OR: 0.69; 95% CI: 0.59–0.81; P < 0.001; I² = 18%) compared with ASPs. Within a subset of studies (n = 6) demonstrating low mortality probability (<14.9%), cefazolin therapy remained protective against failure (OR: 0.70; P < 0.001; I² = 39%) and mortality (OR: 0.70; P < 0.001; I² = 35%). Within the high mortality probability (>15%) subset, no significant differences for failure or mortality were noted. The risk of adverse events was higher with ASPs (OR: 2.58; 95% CI: 1.00–6.64; P = 0.05).

Conclusion

Cefazolin was associated with significantly lower rates of failure, mortality, and treatment-related adverse events when compared with ASPs among less severely ill patients. Prospective, randomized controlled trials are needed to establish the role of these agents in serious MSSA BSI.

Disclosures

All authors: No reported disclosures.

1394. A Translational Pharmacokinetic Rat Model of Cerebral Spinal Fluid (CSF) and Plasma Concentrations of Cefepime

Background

Methods

Results

Conclusion

Disclosures

1391. Vancomycin Area Under the Curve (AUC) to Predict Nephrotoxicity: A Systematic Review and Meta-Analysis of Observational Studies

Background

Methods

Results

Conclusion

Disclosures