"Electronic Phenotyping" Antimicrobials to Facilitate Outpatient Stewardship for Asymptomatic Bacteriuria and Urinary Tract Infection in Renal Transplant

Asymptomatic bacteriuria and urinary tract infection in renal transplant are important antimicrobial stewardship targets but are difficult to identify within electronic medical records. We validated an "electronic phenotype" of antibacterials prescribed for these indications. This may be more useful than billing data in assessing antibiotic indication in this outpatient setting.

Rational Development of a Small-Molecule Activator of CK1γ2 That Decreases C99 and Beta-Amyloid Levels

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder characterized by the accumulation of β-amyloid (Aβ), C99, and Tau in vulnerable areas of the brain. Despite extensive research, current strategies to lower Aβ levels have shown limited efficacy in slowing the cognitive decline associated with AD. Recent findings suggest that C99 may also play a crucial role in the pathogenesis of AD. Our laboratory has discovered that CK1γ2 phosphorylates Presenilin 1 at the γ-secretase complex, leading to decreased C99 and Aβ levels. Thus, CK1γ2 activation appears as a promising therapeutic target to lower both C99 and Aβ levels. In this study, we demonstrate that CK1γ2 is inhibited by intramolecular autophosphorylation and describe a high-throughput screen designed to identify inhibitors of CK1γ2 autophosphorylation. We hypothesize that these inhibitors could lead to CK1γ2 activation and increased PS1-Ser367 phosphorylation, ultimately reducing C99 and Aβ levels. Using cultured cells, we investigated the impact of these compounds on C99 and Aβ concentrations and confirmed that CK1γ2 activation effectively reduced their levels. Our results provide proof of concept that CK1γ2 is an attractive therapeutic target for AD. Future studies should focus on the identification of specific compounds that can inhibit CK1γ2 autophosphorylation and evaluate their efficacy in preclinical models of AD. These studies will pave the way for the development of novel therapeutics for the treatment of AD.

Comprehensive guidance for antibiotic dosing in obese adults: 2022 update

Drug dosing in obese patients continues to be challenging due to a lack of high-quality evidence to guide dosing recommendations. We first published guidance for antibiotic dosing in obese adults in 2017, in which we critically reviewed articles identified from a broad search strategy to develop dosing recommendations for 35 antimicrobials. In this updated narrative review, we searched Pubmed, Web of Science, and the Cochrane Library using Medical Subject Headings including anti-infectives, specific generic antimicrobial names, obese, pharmacokinetics, and others. We reviewed 393 articles, cross-referenced select cited references, and when applicable, referenced drug databases, package inserts, and clinical trial data to update dosing recommendations for 41 antimicrobials. Most included articles were pharmacokinetic studies, other less frequently included articles were clinical studies (mostly small, retrospective), case reports, and very rarely, guidelines. Pharmacokinetic changes are frequently reported, can be variable, and sometimes conflicting in this population, and do not always translate to a documented difference in clinical outcomes, yet are used to inform dosing strategies. Extended infusions, high doses, and therapeutic drug monitoring remain important strategies to optimize dosing in this population. Additional studies are needed to clinically validate proposed dosing strategies, clarify optimal body size descriptors, dosing weight scalars, and estimation method of renal function in obese patients.

Validity of Coronavirus Disease 2019 International Classification of Diseases, Tenth Revision in the Urgent Care Setting and Impact on Antibiotic Prescribing Rates

We validated  different coronavirus disease 2019 (COVID-19) International Classification of Diseases, Tenth Edition (ICD-10) encounter definitions across 2 urgent care clinics. Sensitivity of definitions varied throughout the pandemic. Inclusion of COVID-19 and COVID-19-like illness (CLI) ICD-10s rendered highest sensitivity but lowest specificity. Antibiotic prescribing rates were low for COVID-19 ICD-10 encounters, increasing with CLI ICD-10 encounters.

Risk factors and outcomes associated with persistent vancomycin resistant Enterococcal Bacteremia

Background

Prior studies have identified that vancomycin resistant enterococcus (VRE) bacteremia that persists for four days or more is an independent predictor of mortality. Despite this, there is no published data to identify those patients at highest risk of developing persistent VRE bacteremia.

Methods

This was a single center, retrospective, case-control study of adult patients with a VRE bloodstream infection (BSI). Case patients were those with persistent bacteremia (≥ 4 days despite VRE-directed therapy) and control patients were those with non-persistent bacteremia. Logistic regression was used to assess risk factors associated with persistent VRE BSIs. Secondary outcomes included in-hospital mortality, recurrent bacteremia, and breakthrough bacteremia.

Results

During the study period, 24/108 (22%) patients had persistently positive blood cultures. Risk factors for persistent bacteremia included severe neutropenia (OR 2.13), 4 out of 4 positive index blood cultures (OR 11.29) and lack of source control (OR 11.88). In an unadjusted analysis, no statistically significant differences in in-hospital mortality (58% versus 40%; p = 0.121), recurrent bacteremia (17% versus 6%; p = 0.090), or breakthrough bacteremia (13% versus 7%; p = 0.402) were observed between groups.

Conclusion

Patients with severe neutropenia, 4 out of 4 positive index blood culture bottles, and lack of source control were more likely to develop persistent VRE bacteremia despite directed antibiotic treatment.

Sustained Reduction in Urgent Care Antibiotic Prescribing During the COVID-19 pandemic: An Academic Medical Center’s Experience

We compared antibiotic prescribing before and during the ­coronavirus disease 2019 (COVID-19) pandemic at 2 academic urgent care clinics and found a sustained decrease in prescribing driven by respiratory encounters and despite transitioning to telemedicine. Antibiotics were rarely prescribed during encounters for COVID-19 or COVID-19 symptoms. COVID-19 revealed opportunities for outpatient stewardship programs.

Discontinuation Patterns and Cost Avoidance of a Pharmacist-Driven Methicillin-Resistant Staphylococcus aureus Nasal Polymerase Chain Reaction Testing Protocol for De-escalation of Empiric Vancomycin for Suspected Pneumonia

A pharmacist-driven methicillin-resistant Staphylococcus aureus (MRSA) nasal polymerase chain reaction (PCR)-based testing protocol with a 70% acceptance rate for vancomycin discontinuation within 24 hours of negative results significantly reduced unnecessary vancomycin use with an estimated cost avoidance of $40 per vancomycin course. We found high concordance (141 of 147, 96%) of culture-based versus PCR-based MRSA nasal screening.

1489. Safety and Performance of a Pharmacist-Driven Nasal MRSA PCR Protocol for De-escalation of Empiric Vancomycin for Suspected Pneumonia at an Academic Medical Center

Background

Limited published data supports the de-escalation of empiric anti-methicillin resistant Staphylococcus aureus (MRSA) antibiotics for suspected pneumonia upon negative nasal MRSA screening. Besides limited sample sizes, special populations, such as those who are immunocompromised and/or critically ill, have been underrepresented in these reports. We describe real-world efficacy and safety of a pharmacist-driven nasal MRSA PCR testing protocol implemented at Stanford Health Care in May 2018 across a diverse patient population.

Methods

This was an observational cohort study of adult patients who received vancomycin for empiric pneumonia before (PRE) vs after (POST) implementation of a pharmacist-driven nasal MRSA PCR testing protocol (between 05/01/2017 - 08/31/2017 (PRE) and 5/7/2018 - 12/31/2019 (POST). The primary outcome measure was duration of vancomycin administration. Secondary outcomes included time to vancomycin discontinuation, frequency of restarting vancomycin for empiric pneumonia within 7 days, acute kidney injury (defined as “risk” by RIFLE criteria), and MRSA respiratory cultures. Statistical methods are described in Figure A.

Figure A. Statistical methods

Results

Total of 610 patients were included in this study with 116 in the PRE group and 494 in the POST group. Over 40% were critically ill and approximately 37% were immunocompromised in both groups (Table 1). For the primary outcome, median vancomycin duration was significantly shorter in the POST group (1.29 days; 95% CI 1.13-1.45) vs. PRE group (1.98 days; 95% CI 1.49-2.46) (p < 0.0005), a 34.8% reduction (Figure 1). Median vancomycin duration was lower in patients with a negative vs positive nasal MRSA PCR (1.20 days [95% CI 1.08-1.33] vs 2.53 days [95% CI 1.77-3.29], p < 0.0005), a 52.6% reduction (Figure 2). MRSA was recovered in respiratory cultures in 1.7% vs 1.4% in the PRE vs POST groups. One (0.002%) patient had a negative nasal MRSA PCR but culture-confirmed MRSA pneumonia and recovered after completing a treatment course. Secondary safety outcomes were similar between groups (Table 2).

Tables 1 and 2: Baseline Characteristics and Secondary Outcomes

Figure 1. Primary Outcome: Kaplan–Meier Estimates of Cumulative Active Vancomycin Therapy Before and After Implementation of Nasal MRSA PCR protocol

Figure 2. Secondary Outcome: Figure 2. Kaplan–Meier Estimates of Cumulative Active Vancomycin Therapy in Patients with Negative vs Positive Nasal MRSA PCR

Conclusion

Pharmacist-driven nasal MRSA PCR testing is effective and safe in early de-escalation of empiric vancomycin used for pneumonia treatment in a diverse population including critically ill and immunocompromised patients.

Disclosures

All Authors: No reported disclosures

2640. Aerosol vs. Oral Ribavirin for the Treatment of Community-Acquired Respiratory Virus Infections in Lung Transplant Recipients

Background

Community-acquired respiratory virus (CARV) infections are associated with an increased risk of chronic lung allograft dysfunction (CLAD) and graft loss in lung transplant recipients (LTR). Administration of ribavirin by aerosol was the standard of care at Stanford Health Care in the management of CARV infections. Given the sparse evidence of benefit with aerosol ribavirin (AR) and its increasing cost and teratogenic risk for exposed healthcare personnel, AR was restricted to the treatment of respiratory syncytial virus (RSV) in 2016 and was ultimately removed from formulary in 2017. Oral (PO) ribavirin was used at the discretion of the transplant team. The objective of this study was to evaluate the clinical outcomes of AR compared with PO ribavirin in lung transplant recipients.

Methods

We performed a retrospective cohort analysis of adult lung transplant recipients diagnosed with CARV (metapneumovirus, parainfluenza virus, and RSV) infections treated with either AR or PO ribavirin. The analysis included the first treatment course of ribavirin by either route and patients were excluded if they received ribavirin in the prior 12 months. The primary outcome was the development/progression of CLAD, acute organ rejection, and overall mortality.

Results

Of 85 patients, 41 received AR and 44 received PO ribavirin. There was no significant difference in the following clinical outcomes with AR and oral ribavirin, respectively: development or progression of CLAD (30 days: 9.7% vs. 4.5%, P = 0.4227; 90 days: 14.6% vs. 6.8%, P = 0.303; 6 months: 17% vs. 9%, P = 0.3413; 12 months: 24% vs. 15.9%, P = 0.4188), acute organ rejection (90 days: 7.3% vs. 4.5%, P = 0.6689; 6 months: 12.1% vs. 9%, P = 0.7329; 12 months: 19.5% vs. 13.6%, P = 0.5635), and overall mortality (30 days: 0% vs. 4.5%, P = 0.4947; 90 days: 7.3% vs. 4.5%, P = 0.6689; 6 months: 7.3% vs. 9%, P = 1.0; 12 months: 7.3% vs. 13.6%, P = 0.4858). There was no observable difference in reported adverse effects between AR and PO ribavirin.

Conclusion

Lung transplant recipients with CARV infections had similar outcomes when treated with AR or PO ribavirin. Oral ribavirin is a less costly treatment than AR, but the efficacy of ribavirin by any route remains questionable.

Disclosures

All authors: No reported disclosures.

210. Step-down from IV to oral therapy in patients with bacteremia due to Enterobacteriaceae: fluoroquinolones (FQ) vs. ß-lactams (BL) or trimethoprim-sulfamethoxazole (TMP-SMX)

Background

Methods

Results

Conclusion

Disclosures

1984. A Multi-Disciplinary Team-based Quality Improvement Initiative to Reduce Clostridioides difficile Rates and Promote Antimicrobial Stewardship in Targeted Surgical Wards

Background

At Stanford, two surgical wards, E3 and F3, were responsible for 1/5 of hospital-acquired Clostridioides difficile infection (HO CDI) cases in the fiscal year 2018 (FY2018). We used a quality improvement framework with a goal to reduce yearly HO CDI episodes by 1/2 on these wards.

Methods

A multidisciplinary quality improvement team was created with frontline nursing leaders and representatives from colorectal surgery, gynecology oncology, antimicrobial stewardship (ASP), infection prevention, and pharmacy. Coaching and instruction on quality improvement were provided as part of Stanford’s “Realizing Improvement through Team Empowerment” (RITE) program. Using A3 problem solving, root cause analysis identified key drivers, and interventions were performed. Cumulative HO CDI cases in FY2019 and weekly antibiotic days of therapy (DOT) on E3/F3 were monitored.

Results

Review of FY2018 HO CDI cases (n = 14) revealed the most common key driver as inappropriate antibiotic prescribing (8 cases, 57%). Multiple interventions were instituted (Figure 1). Three ASP interventions began February 2019: nursing questioned antibiotic choice/duration on daily interdisciplinary rounds (Figure 2), automatic infectious disease consultation for > 72 hours of piperacillin/tazobactam on gynecology/oncology patients, and twice-weekly rounds between ASP and a colorectal attending. Data from ASP/colorectal rounds from March 19, 2019 to April 16, 2019 showed means of 18.2 minutes taken for chart review and 4.4 minutes for discussion. 25 charts reviewed led to 16 (64%) ASP recommendations and 14/16 (87.5%) of recommendations accepted. Common interventions included: appropriate duration of antibiotics, clarification of the team’s planned duration, and review of microbiology data to narrow therapy. Mean DOT decreased from 35.28 to 21.61 (39%) since July 2018 (Figure 3). Patient volume and case mix index remained stable throughout, suggesting no impact on DOT. Though CDI cases did not decrease, interventions were in place for only 2 months (Figure 4).

Conclusion

While too early to determine its impact on HO CDI rates, a multi-disciplinary team approach utilizing A3 problem solving was successful in implementing effective ASP measures including nursing-led ASP and structured antibiotic timeouts.

Disclosures

All authors: No reported disclosures.

Development of Kinase Inactive PD173955 Analogues for Reducing Production of Aβ Peptides

Compound 3a, DV2-103, is a kinase inactive analogue of a potent Abl1/Src kinase inhibitor, PD173955, 2. Both compounds, 2 and 3a, are known to reduce production of beta amyloid (Aβ) peptide in cells and animal models. We have now prepared and evaluated a series of PD-173955 analogues, several of which reduced Aβ production potently. This occurs in cells expressing human full-length amyloid precursor protein (APP) and not in cells expressing APP β-C terminal fragment (APP-C99), suggesting that the kinase inactive analogues strongly affect β-secretase (BACE1) cleavage of APP, similarly to Gleevec. A combination of the kinase inactive analogues of PD173955 with a BACE1 inhibitor (BACEi), namely, BACE IV, strongly reduced Aβ levels in cells, as noted previously with Gleevec and analogues. Several potent compounds also penetrated and accumulated in mouse brain in high nanomolar to low micromolar concentration.

Conversion from Vancomycin Trough Concentration-Guided Dosing to Area Under the Curve-Guided Dosing Using Two Sample Measurements in Adults: Implementation at an Academic Medical Center

STUDY OBJECTIVE

The optimal pharmacodynamic parameter for the prediction of efficacy of vancomycin is the area under the concentration-time curve (AUC), and current published data indicate that dosing based on vancomycin trough concentrations is an inaccurate substitute. In this study, our objective was to compare the achievement of therapeutic target attainment after switching from a trough-based to an AUC-based dosing strategy as a part of our institution's vancomycin-per-pharmacy protocol.

DESIGN

Prospective observational quality assurance study.

SETTING

Academic medical center.

PATIENTS

A total of 296 hospitalized adults who received vancomycin and monitoring under our institution's vancomycin-per-pharmacy protocol were included in the analysis. The preimplementation retrospective comparison group consisted of 179 patients in whom vancomycin was initiated using a trough-based dosing strategy between November 22, 2017, and January 22, 2018. The postimplementation group included 117 patients in whom vancomycin was initiated using an AUC-based dosing strategy using two-point sampling between June 19, 2018, and July 19, 2018, after hospital-wide implementation of this protocol on June 19, 2018.

MEASUREMENTS AND MAIN RESULTS

AUC values were calculated from two vancomycin concentrations (peak and trough). The primary outcome was achievement of therapeutic AUC values (400-800 mg·hr/L) in the postimplementation group or therapeutic trough level values (10-20 mg/L) in the preimplementation group. Only 98 (55%) of 179 initial trough values were therapeutic in the preimplementation group (trough-only dosing method) versus 86 (73.5%) of 117 initial AUC values in the postimplementation group (AUC-based dosing method) (p=0.0014). A lower proportion of supratherapeutic AUC values was observed in the postimplementation group compared with supratherapeutic trough concentrations in the preimplementation group (1.7% vs 18%, p<0.0001). Overall, 62% of patients with initially therapeutic AUC values had subsequent trough value increases of 25% or greater, occurring at a median of 6 days of vancomycin therapy. Nephrotoxicity occurred in 11% of patients in the preimplementation versus 9.4% in the postimplementation group (p=0.70).

CONCLUSION

Compared with a trough concentration-based dosing strategy, AUC-based dosing using two-point sampling improved therapeutic target attainment. Implementation is feasible at any hospital that performs vancomycin peak concentration testing and is a workable alternative to using Bayesian software for estimating AUC. This approach should also be directly compared with AUC-based dosing using Bayesian software.

Type I and type II fatty acid biosynthesis in Eimeria tenella: enoyl reductase activity and structure

Apicomplexan parasites of the genus Eimeria are the major causative agent of avian coccidiosis, leading to high economic losses in the poultry industry. Recent results show that Eimeria tenella harbours an apicoplast organelle, and that a key biosynthetic enzyme, enoyl reductase, is located in this organelle. In related parasites, enoyl reductase is one component of a type II fatty acid synthase (FAS) and has proven to be an attractive target for antimicrobial compounds. We cloned and expressed the mature form of E. tenella enoyl reductase (EtENR) for biochemical and structural studies. Recombinant EtENR exhibits NADH-dependent enoyl reductase activity and is inhibited by triclosan with an IC50 value of 60 nm. The crystal structure of EtENR reveals overall similarity with other ENR enzymes; however, the active site of EtENR is unoccupied, a state rarely observed in other ENR structures. Furthermore, the position of the central beta-sheet appears to block NADH binding and would require significant movement to allow NADH binding, a feature not previously seen in the ENR family. We analysed the E. tenella genomic database for orthologues of well-characterized bacterial and apicomplexan FAS enzymes and identified 6 additional genes, suggesting that E. tenella contains a type II FAS capable of synthesizing saturated, but not unsaturated, fatty acids. Interestingly, we also identified sequences that appear to encode multifunctional type I FAS enzymes, a feature also observed in Toxoplasma gondii, highlighting the similarity between these apicomplexan parasites.

Enzymes of type II fatty acid synthesis and apicoplast differentiation and division in Eimeria tenella

Apicomplexan parasites, Eimeria tenella, Plasmodium spp. and Toxoplasma gondii, possess a homologous plastid-like organelle termed the apicoplast, derived from the endosymbiotic enslavement of a photosynthetic alga. However, currently no eimerian nuclear encoded apicoplast targeted proteins have been identified, unlike in Plasmodium spp. and T. gondii. In this study, we demonstrate that nuclear encoded enoyl reductase of E. tenella (EtENR) has a predicted N-terminal bipartite transit sequence, typical of apicoplast-targeted proteins. Using a combination of immunocytochemistry and EM we demonstrate that this fatty acid biosynthesis protein is located in the apicoplast of E. tenella. Using the EtENR as a tool to mark apicoplast development during the Eimeria lifecycle, we demonstrate that nuclear and apicoplast division appear to be independent events, both organelles dividing prior to daughter cell formation, with each daughter cell possessing one to four apicoplasts. We believe this is the first report of multiple apicoplasts present in the infectious stage of an apicomplexan parasite. Furthermore, the microgametes lacked an identifiable apicoplast consistent with maternal inheritance via the macrogamete. It was found that the size of the organelle and the abundance of EtENR varied with developmental stage of the E. tenella lifecycle. The high levels of EtENR protein observed during asexual development and macrogametogony is potentially associated with the increased synthesis of fatty acids required for the rapid formation of numerous merozoites and for the extracellular development and survival of the oocyst. Taken together the data demonstrate that the E. tenella apicoplast participates in type II fatty acid biosynthesis with increased expression of ENR during parasite growth. Apicoplast division results in the simultaneous formation of multiple fragments. The division mechanism is unknown, but is independent of nuclear division and occurs prior to daughter formation.

Delivery of antimicrobials into parasites

To eliminate apicomplexan parasites, inhibitory compounds must cross host cell, parasitophorous vacuole, and parasite membranes and cyst walls, making delivery challenging. Here, we show that short oligomers of arginine enter Toxoplasma gondii tachyzoites and encysted bradyzoites. Triclosan, which inhibits enoyl-ACP reductase (ENR), conjugated to arginine oligomers enters extracellular tachyzoites, host cells, tachyzoites inside parasitophorous vacuoles within host cells, extracellular bradyzoites, and bradyzoites within cysts. We identify, clone, and sequence T. gondii enr and produce and characterize enzymatically active, recombinant ENR. This enzyme has the requisite amino acids to bind triclosan. Triclosan released after conjugation to octaarginine via a readily hydrolyzable ester linkage inhibits ENR activity, tachyzoites in vitro, and tachyzoites in mice. Delivery of an inhibitor to a microorganism via conjugation to octaarginine provides an approach to transporting antimicrobials and other small molecules to sequestered parasites, a model system to characterize transport across multiple membrane barriers and structures, a widely applicable paradigm for treatment of active and encysted apicomplexan and other infections, and a generic proof of principle for a mechanism of medicine delivery.

Measurement of the efficacy of vaccines and antimicrobial therapy against infection with Toxoplasma gondii

To facilitate studies of vaccines and antimicrobial agents effective against Toxoplasma gondii infection, an assay system was developed to semi-quantitate parasitaemia using PCR amplification of T. gondii DNA obtained from the blood of mice infected with the parasite. A competitive internal standard DNA fragment of the B1 gene of T. gondii was generated and used in PCR so that the amplified product could be semi-quantitated and false negative results could be avoided. The PCR assay system was used to analyse the levels of parasitaemia in immunised and antimicrobial agent treated mice at various times after infection with T. gondii. The results of these studies indicate that this highly sensitive detection method is a rapid and reliable procedure that can be employed to assess the abilities of vaccines or antimicrobial agents to provide protection early following T. gondii infection.

Congenital toxoplasmosis transmitted from an immunologically competent mother infected before conception

Congenital transmission of Toxoplasma gondii from a mother who was apparently immunologically competent and who had toxoplasmic lymphadenitis 2 months before conception is described. Since no T. gondii-specific serological data were available for this mother from the time her lymph node biopsy specimen was obtained, the specimen was studied by polymerase chain reaction (PCR) to determine whether the T. gondii B1 gene was present. The predictive diagnostic value of histologic findings previously considered to be classic signs of T. gondii lymphadenitis also was studied. This was done by correlation of serological tests diagnostic of acute acquired T. gondii infection and presence of characteristic findings in biopsy specimens from persons without known immunocompromise. Both PCR and review of the characteristic features of her lymph node biopsy specimen confirmed the diagnosis of preconceptual infection in the mother. We also discuss two other cases in which apparently immunologically competent mothers with preconceptually acquired infection transmitted this parasite to their fetuses.