Assessing Clinician Utilization of Next-Generation Antibiotics Against Resistant Gram-Negative Infections in U.S. Hospitals : A Retrospective Cohort Study

BACKGROUND

The U.S. antibiotic market failure has threatened future innovation and supply. Understanding when and why clinicians underutilize recently approved gram-negative antibiotics might help prioritize the patient in future antibiotic development and potential market entry rewards.

OBJECTIVE

To determine use patterns of recently U.S. Food and Drug Administration (FDA)-approved gram-negative antibiotics (ceftazidime-avibactam, ceftolozane-tazobactam, meropenem-vaborbactam, plazomicin, eravacycline, imipenem-relebactam-cilastatin, and cefiderocol) and identify factors associated with their preferential use (over traditional generic agents) in patients with gram-negative infections due to pathogens displaying difficult-to-treat resistance (DTR; that is, resistance to all first-line antibiotics).

DESIGN

Retrospective cohort.

SETTING

619 U.S. hospitals.

PARTICIPANTS

Adult inpatients.

MEASUREMENTS

Quarterly percentage change in antibiotic use was calculated using weighted linear regression. Machine learning selected candidate variables, and mixed models identified factors associated with new (vs. traditional) antibiotic use in DTR infections.

RESULTS

Between quarter 1 of 2016 and quarter 2 of 2021, ceftolozane-tazobactam (approved 2014) and ceftazidime-avibactam (2015) predominated new antibiotic usage whereas subsequently approved gram-negative antibiotics saw relatively sluggish uptake. Among gram-negative infection hospitalizations, 0.7% (2551 [2631 episodes] of 362 142) displayed DTR pathogens. Patients were treated exclusively using traditional agents in 1091 of 2631 DTR episodes (41.5%), including "reserve" antibiotics such as polymyxins, aminoglycosides, and tigecycline in 865 of 1091 episodes (79.3%). Patients with bacteremia and chronic diseases had greater adjusted probabilities and those with do-not-resuscitate status, acute liver failure, and Acinetobacter baumannii complex and other nonpseudomonal nonfermenter pathogens had lower adjusted probabilities of receiving newer (vs. traditional) antibiotics for DTR infections, respectively. Availability of susceptibility testing for new antibiotics increased probability of usage.

LIMITATION

Residual confounding.

CONCLUSION

Despite FDA approval of 7 next-generation gram-negative antibiotics between 2014 and 2019, clinicians still frequently treat resistant gram-negative infections with older, generic antibiotics with suboptimal safety-efficacy profiles. Future antibiotics with innovative mechanisms targeting untapped pathogen niches, widely available susceptibility testing, and evidence demonstrating improved outcomes in resistant infections might enhance utilization.

PRIMARY FUNDING SOURCE

U.S. Food and Drug Administration; NIH Intramural Research Program.

The microbiological outcomes of culture-negative blood specimens using 16S rRNA broad-range PCR sequencing: a retrospective study in a Canadian province from 2018 to 2022

Broad-range 16S rRNA PCR and sequencing of 1,183 blood specimens from 853 unique patients yielded an interpretable sequence and bacterial identification in 29%, 16S rRNA amplification with uninterpretable sequences in 53%, and no amplification in 18%. This study highlights the potential utility of this technique in identifying fastidious gram-negative and anaerobic bacteria but the frequent recovery of environmental and contaminant organisms argues for its judicious use.

IMPORTANCE

The existing literature focuses on its performance compared to blood cultures in patients with sepsis, leaving a gap in the literature regarding other blood specimens in suspected infectious syndrome across the severity spectrum. We aimed to characterize its microbiological outcomes and provide insight into its potential clinical utility.

Rapid phenotypic testing for detection of carbapenemase- or extended-spectrum ß-lactamase-producing Enterobacterales directly from blood cultures: a systematic review and meta-analysis

BACKGROUND

Early identification of extended-spectrum ß-lactamase (ESBL) and carbapenemase-producing Enterobacterales (CP-CRE) is critical for timely therapy. Rapid phenotypic tests identifying these resistance mechanisms from pure bacterial colonies have been developed.

OBJECTIVES

To determine the operating characteristics of available rapid phenotypic tests when applied directly to positive blood cultures.

METHODS OF DATA SYNTHESIS

Bivariate random effects models were used unless convergence was not achieved where we used separate univariate models for sensitivity and specificity.

DATA SOURCES

MEDLINE, CENTRAL, Embase, BIOSIS, and Scopus from inception to 16 March 2021.

STUDY ELIGIBILITY CRITERIA

Studies using any rapid phenotypic assay for detection of ESBL or CP-CRE directly from blood cultures positive for Enterobacterales, including those utilizing spiked blood cultures. Case reports/series, posters, abstracts, review articles, those with ≤5 resistant isolates, and studies lacking data or without full text were excluded.

PARTICIPANTS

Consecutive patient samples (main analysis) or spiked blood cultures (sensitivity analysis).

TESTS

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry assays (MALDI-TOF) and commercially available chromogenic or immunogenic assays.

REFERENCE STANDARD

Conventional laboratory methods and/or polymerase chain reaction (PCR).

ASSESSMENT OF RISK OF BIAS

Quality Assessment of Diagnostic Accuracy Studies Version 2 (QUADAS-2).

RESULTS

For detection of the ESBL phenotype the respective pooled sensitivities and specificities for consecutive clinical samples were as follows: 94% (95% CI 93-99%) and 97% (95% CI 95-100%) for MALDI-TOF/mass spectrometry (n = 1); and 98% (95% CI 92-100%) and 100% (95% CI 96-100%) for chromogenic assays (n = 7). For the CP-CRE phenotype the respective pooled sensitivity and specificities for consecutive clinical samples were as follows: 100% (95% CI 99-100%) and 100% (95% CI 100-100%) for MALDI-TOF (n = 2); 96% (95% CI 77-99%) and 100% (95% CI 81-100%) for chromogenic assays (n = 4); and 98% (95% CI 96-100%) and 100% (95% CI 100-100%) for immunogenic testing (n = 2).

CONCLUSIONS

Rapid phenotypic assays that can be directly applied to positive blood cultures to detect ESBL and carbapenemase production from Enterobacterales exist and, although clinical studies are limited, they appear to have high sensitivity and specificity. Their potential to facilitate patient care through timely identification of bacterial resistance should be further explored.

Microbiological characterization of Pneumocystis jirovecii pneumonia using quantitative PCR from nasopharyngeal specimens: a retrospective study in a Canadian province from 2019 to 2023

Bronchoalveolar lavage is usually employed for molecular diagnosis of Pneumocystis jirovecii but requires a specialized procedure. By contrast, nasopharyngeal (NP) specimens are easily obtained. In this retrospective study of 35 patients with paired NP and bronchoscopy specimens, NP specimens had a 100% negative percent agreement (95% CI 80.5-100) but only 72.2% positive percent agreement (95% CI 46.5-90.3).

Reliability of Admission Procalcitonin Testing for Capturing Bacteremia Across the Sepsis Spectrum: Real-World Utilization and Performance Characteristics, 65 U.S. Hospitals, 2008-2017

OBJECTIVES

Serum procalcitonin is often ordered at admission for patients with suspected sepsis and bloodstream infections (BSIs), although its performance characteristics in this setting remain contested. This study aimed to evaluate use patterns and performance characteristics of procalcitonin-on-admission in patients with suspected BSI, with or without sepsis.

DESIGN

Retrospective cohort study.

SETTING

Cerner HealthFacts Database (2008-2017).

PATIENTS

Adult inpatients (≥ 18 yr) who had blood cultures and procalcitonin drawn within 24 hours of admission.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Testing frequency of procalcitonin was determined. Sensitivity of procalcitonin-on-admission for detecting BSI due to different pathogens was calculated. Area under the receiver operating characteristic curve (AUC) was calculated to assess discrimination by procalcitonin-on-admission for BSI in patients with and without fever/hypothermia, ICU admission and sepsis defined by Centers for Disease Control and Prevention Adult Sepsis Event criteria. AUCs were compared using Wald test and p values were adjusted for multiple comparisons. At 65 procalcitonin-reporting hospitals, 74,958 of 739,130 patients (10.1%) who had admission blood cultures also had admission procalcitonin testing. Most patients (83%) who had admission day procalcitonin testing did not have a repeat procalcitonin test. Median procalcitonin varied considerably by pathogen, BSI source, and acute illness severity. At a greater than or equal to 0.5 ng/mL cutoff, sensitivity for BSI detection was 68.2% overall, ranging between 58.0% for enterococcal BSI without sepsis and 96.4% for pneumococcal sepsis. Procalcitonin-on-admission displayed moderate discrimination at best for overall BSI (AUC, 0.73; 95% CI, 0.72-0.73) and showed no additional utility in key subgroups. Empiric antibiotic use proportions were not different between blood culture sampled patients with a positive procalcitonin (39.7%) and negative procalcitonin (38.4%) at admission.

CONCLUSIONS

At 65 study hospitals, procalcitonin-on-admission demonstrated poor sensitivity in ruling out BSI, moderate-to-poor discrimination for both bacteremic sepsis and occult BSI and did not appear to meaningfully alter empiric antibiotic usage. Diagnostic stewardship of procalcitonin-on-admission and risk assessment of admission procalcitonin-guided clinical decisions is warranted.

Association between piperacillin/tazobactam MIC and survival among hospitalized patients with Enterobacterales infections: retrospective cohort analysis of electronic health records from 161 US hospitals

Introduction

A recent randomized trial has suggested an increased risk of mortality for ceftriaxone-non-susceptible Enterobacterales infections treated with piperacillin/tazobactam compared with meropenem despite MICs within the susceptible range.

Methods

We conducted a retrospective cohort study of clinical encounters within the Cerner Health Facts database to identify all encounters between 2001 and 2017 in which Enterobacterales infections were treated empirically with piperacillin/tazobactam and for which MICs to the drug were available. Multivariate regression analysis was performed to enable partitioning of MICs into discrete strata based on statistically significant difference in mortality risk.

Results

During the study period, 10 101 inpatient encounters were identified meeting inclusion criteria. The crude in-hospital mortality for the entire cohort was 16.5%. Partitioning analysis identified a breakpoint of ≤16/4 mg/L that dichotomized encounters into lower versus higher mortality risk strata in the primary cohort of overall infections. This finding persisted in sequentially granular subsets where specific MICs ≤8/4 mg/L were reported (in lieu of ranges) as well as in the high-reliability subset with bloodstream infections. A higher clinical breakpoint of ≥128/4 mg/L dichotomized encounters with respiratory tract infection. No breakpoint was identified when restricting to encounters with urinary tract infections, ICU admits or upon restricting analysis to encounters with ceftriaxone-resistant isolates.

Conclusions

Clinical data suggest improved outcomes when piperacillin/tazobactam is prescribed for Enterobacterales infections with an MIC of ≤16/4 mg/L compared with ≥32/4 mg/L.

Association between minimum inhibitory concentration values and mortality risk in patients with Stenotrophomonas maltophilia infections: a retrospective cohort study of electronic health records from 148 US hospitals

Background

Clinical data informing antimicrobial susceptibility breakpoints for Stenotrophomonas maltophilia infections are lacking. We sought to leverage real-world data to identify MIC values within the currently defined susceptible range that could discriminate mortality risk for patients with S. maltophilia infections and guide future breakpoint revisions.

Methods

Inpatients with S. maltophilia infection who received single-agent targeted therapy with levofloxacin or trimethoprim/sulfamethoxazole were identified in the Cerner HealthFacts electronic health record database. Encounters were restricted to those with MIC values reported to be in the susceptible range for both agents. Curation for exact (non-range) MIC values yielded sequentially granular model populations. Logistic regression was used to calculate adjusted OR (aOR) of mortality or hospice discharge associated with different susceptible-range MICs, controlling for patient- and centre-related factors, and infection site, polymicrobial infection and receipt of empirical therapy.

Results

Seventy-three of 851 levofloxacin-treated patients had levofloxacin MIC of exactly 2 mg/L (current Clinical and Laboratory Standards Institute (CLSI) susceptibility breakpoint) and served as the reference category for levofloxacin breakpoint models. In breakpoint model I (n = 501), aOR of mortality associated with infection due to isolates with levofloxacin MIC of ≤1 versus 2 mg/L were similar [aOR = 1.79 (95% CI 0.88-3.62), P = 0.11]. In breakpoint model IIa (n = 358), aOR of mortality associated with MIC ≤0.5 versus 2 mg/L were also similar [aOR 0.1.36 (95% CI 0.65-2.83), P = 0.41]. However, breakpoint model IIb (n = 297) displayed higher aOR of mortality associated with an MIC of 1 versus 2 mg/L [aOR 2.36 (95% CI 1.14-4.88), P = 0.02]. Only 9/645 trimethoprim/sulfamethoxazole-treated patients had trimethoprim/sulfamethoxazole MIC of exactly 2/38 mg/L precluding informative models for this agent.

Conclusions

In this retrospective study of real-world patients with S. maltophilia infection, risk-adjusted survival data do not appear to stratify patients clinically within current susceptible-range MIC breakpoint for levofloxacin (≤2 mg/L) by mortality.

1649. Ceftolozane-Tazobactam or Ceftazidime-Avibactam Versus Best Available Therapy in the Treatment of Difficult-to-Treat Pseudomonas aeruginosa Infections: a Retrospective Comparative Effectiveness Analysis of 195 U.S. Hospitals, 2016–2020

Background

Infections due to Pseudomonas aeruginosa displaying difficult-to-treat resistance (DTR-PA) necessitate the use of sub-efficacious and/or toxic “reserve” antibiotics and are associated with considerable morbidity and mortality. Ceftazidime-avibactam (CAZ-AVY) and ceftolozane-tazobactam (CEF-TAZO) are novel ß-lactam/ß-lactamase inhibitors (BLBLI) that tend to retain in vitro activity against DTR-PA. However, little is known about their in vivo effectiveness compared to reserve agents.

Methods

Inpatients aged ≥ 18 years with ≥1 blood, urine, respiratory, or body fluid culture growing DTR-PA who received targeted therapy with either CAZ-AVY, CEF-TAZO, or Best-Available Therapy (BAT) were identified in the Premier Healthcare Database. Primary outcome was in-hospital mortality or discharge to hospice and secondary outcome was length of hospital stay (LOS) for survivors. The primary outcome was compared for CAZ-AVY vs CEF-TAZO and novel agents (CAZ-AVY or CEF-TAZO) vs BAT using overlap weighting and binomial regression with downstream adjustment controlling for patient and treatment characteristics. The secondary outcomes were compared using overlap weighting and poisson regression with downstream adjustment controlling for patient and treatment characteristics.

Results

Between 2016 and 2020, 1,552 patients with DTR-PA infections were identified at 105 hospitals, of which 202 (13.0%) were treated with CAZ-AVY, 906 (58.4%) with CEF-TAZO, and 444 (28.6%) with BAT. Patient characteristics were similar among treatment groups (Table 1, Table 2). Overall crude mortality was 15.5%. The adjusted risk of mortality was lower in patients treated with CAZ-AVI (12.5%, 95% CI 7.9–17.1) vs CEF-TAZO (18.8%, 95% CI 15.9–21.8) for a risk difference of 6.3% (95% 1.1–11.5, p = 0.02). The novel agents were not associated with a reduced mortality risk when collectively compared to BAT (risk difference -1.1%, 95% CI -5.4; 3.2%). LOS favoured novel agents and were comparable for CAZ-AVY and CEF-TAZO.

Conclusion

In this real-world observational study of patients with DTR-PA infections, the novel ß-lactam/ß-lactamase inhibitors were comparably effective against BAT, though the use of CAZ-AVY was associated with a reduced mortality compared to CEF-TAZO.

Disclosures

All Authors: No reported disclosures.

272. Do Empiric Antibiotics Improve Outcomes in Clinically Stable Patients Admitted with COVID-19 Pneumonia? Retrospective Cohort Study of 221 U.S. Hospitals, March 1st, 2020-December 31st, 2020

Background

Patients admitted with COVID19 pneumonia often receive initial empiric antibacterial therapy (IEAT) despite a known low probability of bacterial co-infection. However, evidence supporting this practice is lacking. We studied the impact of IEAT on the risk of in-hospital mortality, clinical deterioration and antibiotic-associated risks in stable inpatients with COVID-19.

Methods

Adult inpatients coded for COVID-19 pneumonia stable (no mechanical ventilation or vasopressors) on admission (+1 day) without a clear indication for antibiotics, were identified at hospitals in the Premier Healthcare Database. Patients who received IEAT, defined as the receipt of ≥ 1 antibacterial agent on admission (+1 day), were compared to a control group, using binomial regression with overlap weight matching and downstream adjustment for baseline characteristics (age, gender, race, admission month, surge index, Elixhauser score, any AOFS organ failure POA, ICU admission on day 0 to +2, receipt of remdesivir, corticosteroids, and tocilizumab). The primary outcome was in-hospital mortality or discharge to hospice; secondary outcomes included need for mechanical ventilation on day2+, and rates of non-POA-acute kidney injury (AKI).

Results

At 221 hospitals between March–December 2020, 39,517 (74%) of 53,431 stable COVID-19 admits received IEAT. Patient and encounter characteristics are shown in Table 1. The crude mortality rates were 12.2% in IEAT recipients and 10.9% in controls. In adjusted analysis of patients who survived beyond admission day, mortality was 11.57% (95% CI 11.24-11.90%) in IEAT recipients and 11.23% (95% CI 10.72-11.74) in controls, for a difference of 0.34% (95% CI -0.23-0.91%, p = 0.24). Subsequent mechanical ventilation occurred similarly between groups (5.72% vs. 5.77%, p=0.83). The adjusted rate of AKI was 2.47% (95% CI 2.31-2.64%) in IEAT recipients, and 3.04% (95% CI 2.74-3.35%) in controls, for a difference of -0.57% (95% CI -0.92-0.22%, p = 0.0014). Table 1.

652. Ceftazidime-avibactam Alone or as Combination Therapy? Multicenter Retrospective Cohort Analysis of Clinical Outcomes in Patients with Carbapenem-resistant Gram-negative Infection

Background

Ceftazidime-avibactam (caz-avi), a novel β-lactam/β-lactamase inhibitor, is commonly utilized for carbapenem-resistant gram-negative infections (CR-GNI). However, the benefits vs risks of combining caz-avi with other agents are unclear.

Methods

In this retrospective cohort study, inpatients with CR-GNI treated with caz-avi were identified at 9 U.S. hospitals. The impact of caz-avi monotherapy (MT) or combination therapy (CT; i.e., any concomitant use of gram-negative-active antibiotics) was studied using logistic regression, controlling for baseline patient and hospital factors. The primary outcome was in-hospital mortality or discharge to hospice (death), and secondary outcomes were length of stay (LOS), resolution of infectious signs and symptoms (clinical response), 90-day recurrent infection and future caz-avi–resistant organism. An adjusted odds ratio (aOR) with 95% confidence interval (CI) was used to assess the primary and secondary outcomes.

Results

328/499 (65.7%) patients received caz-avi as targeted therapy for a CR-GNI. Overall patients treated with MT and CT were similar at baseline and had comparable baseline demographics although patients treated with CT were more likely to be in the ICU and receive a concomitant empiric in vitro-concordant antibiotic (table 1). The most common organism was Klebsiella spp. (44.6%) followed by Pseudomonas aeruginosa (27.7%) (table 2). Concomitant gram-negative agents are shown in table 3. Overall, 92 (28.1%) patients died and CT (vs MT) displayed similar adjusted mortality risk (27.7% vs 28.7%; aOR [95%CI]: 0.67 [0.34-1.33]) and LOS (19 [9, 37] and 20 [9, 42.5] days). CT (vs MT) was associated with greater odds of clinical response (aOR: 2.25 [95%CI:1.15-4.41]). Among survivors, similar rates of 90-day recurrent infection (50/154 (32.5%) were observed in CT vs 18/82 (22.0%) in MT group (p=0.09) and 5 (2.19%) patients had future infection with a caz-avi–resistant pathogen (3 in CT and 2 in MT group).

Conclusion

Compared to patients with CR-GNI treated with caz-avi alone, those who received CT including caz-avy had similar survival and LOS but higher clinical response. The role of CT in the era of novel antibiotics warrants additional study.

Disclosures

Helen W. Boucher, MD, American Society of Microbiology: Honoraria|Elsevier: Honoraria|Sanford Guide: Honoraria.

qSOFA does not predict bacteremia in patients with severe manifestations of sepsis

BACKGROUND

Bloodstream infections in septic patients may be missed due to preceding antibiotic therapy prior to obtaining blood cultures. We leveraged the FABLED cohort study to determine if the quick Sequential Organ Failure Assessment (qSOFA) score could reliably identify patients at higher risk of bacteremia in patients who may have false negative blood cultures due to previously administered antibiotic therapy.

METHODS

We conducted a multi-centre diagnostic study among adult patients with severe manifestations of sepsis. Patients were enrolled in one of seven participating centres between November 2013 and September 2018. All patients from the FABLED cohort had two sets of blood cultures drawn prior to the administration of antimicrobial therapy, as well as additional blood cultures within 4 hours of treatment initiation. Participants were categorized according to qSOFA score, with a score ≥2 being considered positive.

RESULTS

Among 325 patients with severe manifestations of sepsis, a positive qSOFA score (defined as a score ≥2) on admission was 58% sensitive (95% CI 48% to 67%) and 41% specific (95% CI 34% to 48%) for predicting bacteremia. Among patients with negative post-antimicrobial blood cultures, a positive qSOFA score was 57% sensitive (95% CI 42% to 70%) and 42% specific (95% CI 35% to 49%) to detect patients who were originally bacteremic prior to the initiation of therapy.

CONCLUSIONS

Our results suggest that the qSOFA score cannot be used to identify patients at risk for occult bacteremia due to the administration of antibiotics pre-blood culture.

Low-dose trimethoprim-sulfamethoxazole for the treatment of Pneumocystis jirovecii pneumonia (LOW-TMP): protocol for a phase III randomised, placebo-controlled, dose-comparison trial

INTRODUCTION

Pneumocystis jirovecii pneumonia (PJP) is an opportunistic infection of immunocompromised hosts with significant morbidity and mortality. The current standard of care, trimethoprim-sulfamethoxazole (TMP-SMX) at a dose of 15-20 mg/kg/day, is associated with serious adverse drug events (ADE) in 20%-60% of patients. ADEs include hypersensitivity reactions, drug-induced liver injury, cytopenias and renal failure, all of which can be treatment limiting. In a recent meta-analysis of observational studies, reduced dose TMP-SMX for the treatment of PJP was associated with fewer ADEs, without increased mortality.

METHODS AND ANALYSIS

A phase III randomised, placebo-controlled, trial to directly compare the efficacy and safety of low-dose TMP-SMX (10 mg/kg/day of TMP) with the standard of care (15 mg/kg/day of TMP) among patients with PJP, for a composite primary outcome of change of treatment, new mechanical ventilation, or death. The trial will be undertaken at 16 Canadian hospitals. Data will be analysed as intention to treat. Primary and secondary outcomes will be compared using logistic regression adjusting for stratification and presented with 95% CI.

ETHICS AND DISSEMINATION

This study has been conditionally approved by the McGill University Health Centre; Ethics approval will be obtained from all participating centres. Results will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04851015.

On the Treatment of Pneumocystis jirovecii Pneumonia: Current Practice Based on Outdated Evidence

Pneumocystis jirovecii pneumonia (PCP) is a common opportunistic infection causing more than 400000 cases annually worldwide. Although antiretroviral therapy has reduced the burden of PCP in persons with human immunodeficiency virus (HIV), an increasing proportion of cases occur in other immunocompromised populations. In this review, we synthesize the available randomized controlled trial (RCT) evidence base for PCP treatment. We identified 14 RCTs that were conducted 25-35 years ago, principally in 40-year-old men with HIV. Trimethoprim-sulfamethoxazole, at a dose of 15-20 mg/kg per day, is the treatment of choice based on historical practice rather than on quality comparative, dose-finding studies. Treatment duration is similarly based on historical practice and is not evidence based. Corticosteroids have a demonstrated role in hypoxemic patients with HIV but have yet to be studied in RCTs as an adjunctive therapy in non-HIV populations. The echinocandins are potential synergistic treatments in need of further investigation.

Association Between Caseload Surge and COVID-19 Survival in 558 U.S. Hospitals, March to August 2020

BACKGROUND

Several U.S. hospitals had surges in COVID-19 caseload, but their effect on COVID-19 survival rates remains unclear, especially independent of temporal changes in survival.

OBJECTIVE

To determine the association between hospitals' severity-weighted COVID-19 caseload and COVID-19 mortality risk and identify effect modifiers of this relationship.

DESIGN

Retrospective cohort study. (ClinicalTrials.gov: NCT04688372).

SETTING

558 U.S. hospitals in the Premier Healthcare Database.

PARTICIPANTS

Adult COVID-19-coded inpatients admitted from March to August 2020 with discharge dispositions by October 2020.

MEASUREMENTS

Each hospital-month was stratified by percentile rank on a surge index (a severity-weighted measure of COVID-19 caseload relative to pre-COVID-19 bed capacity). The effect of surge index on risk-adjusted odds ratio (aOR) of in-hospital mortality or discharge to hospice was calculated using hierarchical modeling; interaction by surge attributes was assessed.

RESULTS

Of 144 116 inpatients with COVID-19 at 558 U.S. hospitals, 78 144 (54.2%) were admitted to hospitals in the top surge index decile. Overall, 25 344 (17.6%) died; crude COVID-19 mortality decreased over time across all surge index strata. However, compared with nonsurging (<50th surge index percentile) hospital-months, aORs in the 50th to 75th, 75th to 90th, 90th to 95th, 95th to 99th, and greater than 99th percentiles were 1.11 (95% CI, 1.01 to 1.23), 1.24 (CI, 1.12 to 1.38), 1.42 (CI, 1.27 to 1.60), 1.59 (CI, 1.41 to 1.80), and 2.00 (CI, 1.69 to 2.38), respectively. The surge index was associated with mortality across ward, intensive care unit, and intubated patients. The surge-mortality relationship was stronger in June to August than in March to May (slope difference, 0.10 [CI, 0.033 to 0.16]) despite greater corticosteroid use and more judicious intubation during later and higher-surging months. Nearly 1 in 4 COVID-19 deaths (5868 [CI, 3584 to 8171]; 23.2%) was potentially attributable to hospitals strained by surging caseload.

LIMITATION

Residual confounding.

CONCLUSION

Despite improvements in COVID-19 survival between March and August 2020, surges in hospital COVID-19 caseload remained detrimental to survival and potentially eroded benefits gained from emerging treatments. Bolstering preventive measures and supporting surging hospitals will save many lives.

PRIMARY FUNDING SOURCE

Intramural Research Program of the National Institutes of Health Clinical Center, the National Institute of Allergy and Infectious Diseases, and the National Cancer Institute.

Suspected SARS-CoV-2 Reinfections: Incidence, Predictors, and Healthcare Use among Patients at 238 U.S. Healthcare Facilities, June 1, 2020- February 28, 2021

In a retrospective cohort study, among 131,773 patients with previous COVID19, reinfection with SARS-CoV-2 was suspected in 253(0.2%) patients at 238 U.S. healthcare facilities between June 1, 2020- February 28, 2021. Women displayed a higher cumulative reinfection risk. Healthcare burden and illness severity were similar between index and reinfection encounters.

Neither Blood Culture Positivity nor Time to Positivity Is Associated With Mortality Among Patients Presenting With Severe Manifestations of Sepsis: The FABLED Cohort Study

Background

Sepsis is a leading cause of morbidity, mortality, and health care costs worldwide.

Methods

We conducted a multicenter, prospective cohort study evaluating the yield of blood cultures drawn before and after empiric antimicrobial administration among adults presenting to the emergency department with severe manifestations of sepsis. Enrolled patients who had the requisite blood cultures drawn were followed for 90 days. We explored the independent association between blood culture positivity and its time to positivity in relation to 90-day mortality.

Results

Three hundred twenty-five participants were enrolled; 90-day mortality among the 315 subjects followed up was 25.4% (80/315). Mortality was associated with age (mean age [standard deviation] in those who died was 72.5 [15.8] compared with 62.9 [17.7] years among survivors; P < .0001), greater Charlson Comorbidity Index (2 [interquartile range {IQR}, 1–3] vs 1 [IQR, 0–3]; P = .008), dementia (13/80 [16.2%] vs 18/235 [7.7%]; P = .03), cancer (27/80 [33.8%] vs 47/235 [20.0%]; P = .015), positive quick Sequential Organ Failure Assessment score (57/80 [71.2%] vs 129/235 [54.9%]; P = .009), and normal white blood cell count (25/80 [31.2%] vs 42/235 [17.9%]; P = .02). The presence of bacteremia, persistent bacteremia after antimicrobial infusion, and shorter time to blood culture positivity were not associated with mortality. Neither the source of infection nor pathogen affected mortality.

Conclusions

Although severe sepsis is an inflammatory condition triggered by infection, its 90-day survival is not influenced by blood culture positivity nor its time to positivity.

Clinical Trials Registration

NCT01867905.

Adjunctive Daptomycin in the Treatment of Methicillin-susceptible Staphylococcus aureus Bacteremia: A Randomized, Controlled Trial

BACKGROUND

Bloodstream infections (BSIs) with methicillin-susceptible Staphylococcus aureus (MSSA) are associated with significant morbidity and mortality. Our objective in this study was to determine the efficacy of synergistic treatment with daptomycin when given with either cefazolin or cloxacillin for the treatment of MSSA BSI.

METHODS

A randomized, double-blind, placebo-controlled trial was performed at 2 academic hospitals in Montreal, Canada. Patients aged ≥18 years with MSSA BSI receiving either cefazolin or cloxacillin monotherapy were considered for inclusion. In addition to the standard-of-care treatment, participants received a 5-day course of adjunctive daptomycin or placebo. The primary outcome was the duration of MSSA BSI in days.

RESULTS

Of 318 participants screened, 115 were enrolled and 104 were included in the intention-to-treat analysis (median age, 67 years; 34.5% female). The median duration of bacteremia was 2.04 days among patients who received daptomycin vs 1.65 days in those who received placebo (absolute difference, 0.39 days; P = .40). In a modified intention-to-treat analysis that involved participants who remained bacteremic at the time of enrollment, we found a median duration of bacteremia of 3.06 days among patients who received daptomycin vs 3.0 days in those who received placebo (absolute difference, 0.06 days; P = .77). Ninety-day mortality in the daptomycin arm was 18.9% vs 17.7% in the placebo arm (P = 1.0).

CONCLUSIONS

Among patients with MSSA BSIs, the administration of adjunctive daptomycin therapy to standard-of-care treatment did not shorten the duration of bacteremia and should not be routinely considered.

CLINICAL TRIALS REGISTRATION

NCT02972983.

Proton Pump Inhibitors Versus Histamine-2 Receptor Antagonists Likely Increase Mortality in Critical Care: An Updated Meta-Analysis

BACKGROUND

Upper gastrointestinal bleeding is common among the critically ill. Recently, the Proton Pump Inhibitors (PPIs) vs. Histamine-2 Receptor Blockers for Ulcer Prophylaxis Therapy in the Intensive Care Unit (PEPTIC) trial suggested PPIs might increase mortality. We performed an updated meta-analysis to further inform discussion.

METHODS

We leveraged 2 recent systematic reviews to identify randomized controlled trials directly comparing PPIs and H-2 Receptor Antagonists (H2RAs) for stress ulcer prophylaxis in critically ill patients and reporting mortality. We extracted mortality data from each study and meta-analyzed them with the PEPTIC trial using a random effects model.

RESULTS

Of 28,559 total patients, 14,436 (50.5%) were allocated to PPI and 14,123 to H2RAs (49.5%). Compared to H2RAs, the pooled relative risk for mortality was 1.05 (95% confidence interval 1.00-1.10) with an estimated risk difference for mortality of 9 additional deaths per 1000 patients exposed to PPI (95% confidence interval 0-18); heterogeneity was low (I² = 0%; P = 0.826).

CONCLUSIONS

Stress ulcer prophylaxis with PPIs likely increases mortality compared to H2RAs. Whether stress ulcer prophylaxis is beneficial in critical care remains open to further study.

Comparison of Saliva and Nasopharyngeal Swab Nucleic Acid Amplification Testing for Detection of SARS-CoV-2: A Systematic Review and Meta-analysis

Importance

Nasopharyngeal swab nucleic acid amplification testing (NAAT) is the noninvasive criterion standard for diagnosis of coronavirus disease 2019 (COVID-19). However, it requires trained personnel, limiting its availability. Saliva NAAT represents an attractive alternative, but its diagnostic performance is unclear.

Objective

To assess the diagnostic accuracy of saliva NAAT for COVID-19.

Data Sources

In this systematic review, a search of the MEDLINE and medRxiv databases was conducted on August 29, 2020, to find studies of diagnostic test accuracy. The final meta-analysis was performed on November 17, 2020.

Study Selection

Studies needed to provide enough data to measure salivary NAAT sensitivity and specificity compared with imperfect nasopharyngeal swab NAAT as a reference test. An imperfect reference test does not perfectly reflect the truth (ie, it can give false results). Studies were excluded if the sample contained fewer than 20 participants or was neither random nor consecutive. The Quality Assessment of Diagnostic Accuracy Studies 2 tool was used to assess the risk of bias.

Data Extraction and Synthesis

Preferred Reporting Items for Systematic Reviews and Meta-analyses reporting guideline was followed for the systematic review, with multiple authors involved at each stage of the review. To account for the imperfect reference test sensitivity, we used a bayesian latent class bivariate model for the meta-analysis.

Main Outcomes and Measures

The primary outcome was pooled sensitivity and specificity. Two secondary analyses were performed: one restricted to peer-reviewed studies, and a post hoc analysis limited to ambulatory settings.

Results

The search strategy yielded 385 references, and 16 unique studies were identified for quantitative synthesis. Eight peer-reviewed studies and 8 preprints were included in the meta-analyses (5922 unique patients). There was significant variability in patient selection, study design, and stage of illness at which patients were enrolled. Fifteen studies included ambulatory patients, and 9 exclusively enrolled from an outpatient population with mild or no symptoms. In the primary analysis, the saliva NAAT pooled sensitivity was 83.2% (95% credible interval [CrI], 74.7%-91.4%) and the pooled specificity was 99.2% (95% CrI, 98.2%-99.8%). The nasopharyngeal swab NAAT had a sensitivity of 84.8% (95% CrI, 76.8%-92.4%) and a specificity of 98.9% (95% CrI, 97.4%-99.8%). Results were similar in secondary analyses.

Conclusions and Relevance

These results suggest that saliva NAAT diagnostic accuracy is similar to that of nasopharyngeal swab NAAT, especially in the ambulatory setting. These findings support larger-scale research on the use of saliva NAAT as an alternative to nasopharyngeal swabs.

12. Evaluation of Rapid Phenotypic Testing for KPC Carbapenemase Producing klebsiella Pneumoniae Directly from Positive Blood Cultures by Use of “Hot Chocolate” Plates

Background

Invasive infections with Carbapenemase Producing Enterobacterales are associated with considerable morbidity and mortality, in part due to the risk of inappropriate empiric therapy. Consequently, the rapid identification of carbapenem resistance is crucial to the management of these infections. We sought to evaluate possible reductions in turnaround time to identification of this resistance in blood cultures growing these organisms by applying rapid phenotypic test kits to growth from “hot chocolate” plates.

Methods

30 blood cultures, spiked with carbapenem resistant Klebsiella pneumoniae isolates or susceptible controls, were inoculated onto chocolate agars that had pre-warmed at 37°C. These plates were incubated at 37ºC for 3.5 hours. The resulting minimal growth was then identified using MALDI-TOF and underwent rapid phenotypic testing using three commercially available products (β-lacta and β-carba, from Bio-Rad, Marnes-la-Coquette, France, and Carba-NP, from bioMérieux, Durham, NC). The time to identification of carbapenem resistance using this method was then compared to that of the conventional laboratory workup.

Results

The identification was 100% accurate to the species level using MALDI-TOF paired to the 3.5 hour growth on the “hot choocolate” plates. The β-lacta kit identified resistance to 3rd generation cephalosporins for all ESBL and carbapenemase producing Klebsiella pneumoniae isolates, while the β-carba and Carba-NP kits identified carbapenem resistance only in the carbapenemase producers. The sensitivity of all assays was 100% (95% CI 0.87–1.0) and the specificity of carbapenemase detection was 100% (97.5% one-sided CI 0.4–1.0). The corresponding sensitivities and specificities of direct disc diffusion for ertapenem resistance detection were 88.5% (95% CI 0.70–0.98) and 100% (95%CI 0.40–1.0) respectively. The turnaround time for the rapid kits coupled to the “hot chocolate” plates was 4.25 to 5.1 hours as compared to 16 hours for the conventional workup.

Conclusion

Rapid phenotypic tests performed after inoculation of “hot chocolate” plates are highly sensitive for the presence of carbapenemase production and can be incorporated into the laboratory workflow for Klebisella pneumoniae with important reductions in turnaround time.

Disclosures

All Authors: No reported disclosures

117. Adjunctive Daptomycin in the Treatment of staphylococcus Aureus Bacteremia

Background

Bloodstream infections (BSI) caused by methicillin-susceptible Staphylococcus aureus (MSSA) are associated with significant morbidity and mortality. The objective of our study was to determine whether daptomycin given in combination with an anti-staphylococcal beta-lactam improved outcomes in MSSA BSI.

Methods

A randomized, double blind, placebo-controlled trial was performed at two academic hospitals in Montreal, Canada. Patients ≥ 18 years of age with MSSA BSI receiving either cefazolin or cloxacillin monotherapy were considered for inclusion. In addition to the standard of care treatment, participants received a 5-day course of adjunctive daptomycin or placebo. The primary outcome was the duration of MSSA BSI in days.

Results

Of 318 participants screened, 115 were enrolled and 104 were included in the intention to treat analysis (median age 67 years; 34.5% female). The median duration of bacteremia was 2.04 days among patients who received daptomycin versus 1.65 days in those who received placebo (absolute difference 0.39 days, p=0.40). A modified intention to treat analysis involving participants who remained bacteremic at the time of enrollment found a median duration of bacteremia of 3.06 days among patients who received daptomycin versus 3.0 days in those who received placebo (absolute difference 0.06 days, p=0.77). Ninety-day mortality in the daptomycin arm was 18.9% vs. 17.7% in the placebo arm (p=1.0). There were no significant differences in the proportion of patients who developed renal failure, hepatotoxicity, or rhabdomyolysis between groups.

Conclusion

Among patients with MSSA BSI, the administration of adjunctive daptomycin therapy to standard of care treatment did not shorten the duration of bacteremia.

Disclosures

All Authors: No reported disclosures

646. Adapting the modified Carbapenem Inactivation Method to assess for possible beta-lactamase mediated resistance in Piperacillin-Tazobactam resistant/ Ceftriaxone susceptible Escherichia. coli and Klebsiella pneumoniae

Background

A cluster of piperacillin-tazobactam resistant/ceftriaxone susceptible Escherichia coli and Klebsiella pneumonaie bacteremias were noted at our institution. A review of the literature suggested this resistance phenotype was mediated by a beta-lactamase. We sought to further corroborate this phenotypically.

Methods

We adapted the “carbapenem inactivation method” utilizing piperacillin-tazobactam and ceftriaxone discs on all E. coli and K. pneumoniae isolated from blood and demonstrating piperacillin-tazobactam resistance but with ceftriaxone susceptibility. We utilized pan-susceptible and carbapenem resistance Enterobacteriaceae reference strains as well as third generation cephalosporin resistant, piperacillin-tazobactam susceptible isolates as controls.

Results

96% of the piperacillin-tazobactam resistant, ceftriaxone susceptible strains demonstrated the capacity to degrade the piperacillin-tazobactam discs while 100% spared the ceftriaxone discs. 75% of the piperacillin-tazobactam susceptible, ceftriaxone resistant control strains spared the piperacillin-tazobactam discs while degrading the ceftriaxone discs.

Conclusion

The resistance phenotype observed is due to beta-lactamase production and the modified carbapenem inactivation method can be adapted to probe for other beta-lactamases. Further study is required to definitively identify which beta-lactamase is responsible.

Disclosures

All Authors: No reported disclosures

Antibody tests have higher sensitivity at ≥15 days after symptom onset and 99% specificity for detecting SARS-CoV-2

SOURCE CITATION

Deeks JJ, Dinnes J, Takwoingi Y, et al. Antibody tests for identification of current and past infection with SARS-CoV-2. Cochrane Database Syst Rev. 2020;6:CD013652. 32584464.

In vitro synergy of β-lactam combinations against KPC-producing Klebsiella pneumoniae strains

BACKGROUND

Double carbapenem therapy has been promoted as an alternative treatment for infections due to carbapenemase-producing Enterobacteriaceae where carbapenemase inhibitors are unavailable or when other agents have demonstrated toxicity with equally limited evidence. The capacity of other β-lactams and β-lactamase inhibitors to provide synergistic activity with carbapenems is unclear.

OBJECTIVES

This study sought to investigate the in vitro synergistic potential of other β-lactam/β-lactamase combinations with meropenem against KPC producers.

METHODS

Time-kill assays were performed on 24 unique strains of KPC-producing Klebsiella pneumoniae. Combinations evaluated included meropenem or imipenem with one of the following: ertapenem, piperacillin/tazobactam or ceftolozane/tazobactam. Concentrations used for each drug were those considered physiologically attainable in patients with a time above the concentration exceeding 40%-50% of the dose interval. Combinations were considered to be synergistic when they reduced bacterial cfu/mL by ≥2 log10 at 24 h as compared with the single most active agent.

RESULTS

The combination of piperacillin/tazobactam with meropenem was found to be synergistic against 70.8% of the isolates, followed by ertapenem with meropenem (58.3%) and ceftolozane/tazobactam with meropenem (41.7%). The piperacillin/tazobactam combination was found to be more bactericidal than the other combinations, with 58.3% of isolates demonstrating a ≥4 log10 cfu/mL reduction at 24 h, as compared with 37.5% for ertapenem and 20.8% for ceftolozane/tazobactam combinations.

CONCLUSIONS

The combination of piperacillin/tazobactam with meropenem may be a potential therapy against KPC-producing K. pneumoniae when other therapies are unavailable or prohibitively toxic.

Clinical Trials Increase Off-Study Drug Use: A Segmented Time-Series Analysis

Background

The effect of participation in a clinical trial on concomitant off-study investigational drug use has not been described. We sought to determine if participation in the Daptomycin as Adjunctive Therapy for Staphylococcus aureus bacteremia (DASH) trial increased overall daptomycin prescribing at study sites.

Methods

We retrospectively analyzed daptomycin use for 8 years preceding the trial, off-study daptomycin use during the trial itself (31 months), and daptomycin use for 6 fiscal months after trial completion. We used a segmented linear regression analysis of an interrupted time series to analyze changes in each drug’s defined daily doses (DDD) per 1000 patient-days. As a control, we analyzed use of linezolid over these periods and also accounted for rates of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) infections.

Results

For 1.5 years before the DASH trial, daptomycin use was decreasing by –0.30 DDD per 1000 patient-days per fiscal period (95% CI, –0.52 to –0.07). Following the initiation of the study, there was a statistically significant increase in daptomycin use of 0.28 DDD per 1000 patient-days per fiscal period (95% CI, 0.03 to 0.52), despite low, stable rates of MRSA and VRE infections. Following trial completion, daptomycin use decreased back toward prestudy rates. Use of linezolid remained stable throughout.

Conclusions

Despite the DASH trial being a negative study, it impacted the prescribing habits of local clinicians during recruitment. Trialists should be aware of potential off-target study effects, and prescribers should be wary of early uptake of interventions before definitive study results.

Real-world Time to Positivity of 2 Widely Used Commercial Blood Culture Systems in Patients With Severe Manifestations of Sepsis: An Analysis of the FABLED Study

Background

Of all microbiological tests performed, blood cultures have the most impact on patient care. Timely results are essential, especially in the management of sepsis. While there are multiple available blood culture systems on the market, they have never been compared in a prospective study in a critically ill population.

Methods

We performed an analysis of the FABLED study cohort to compare culture results and time to positivity (TTP) of 2 widely used blood culture systems: BacT/Alert and BACTEC. In this multisite prospective study, patients with severe manifestations of sepsis had cultures drawn before antibiotics using systematic enrollment criteria and blood drawing methodology allowing for minimization of pre-analytical biases.

Results

We enrolled 315 patients; 144 had blood cultures (47 positive) with BacT/Alert and 171 with BACTEC (53 positive). Patients whose blood cultures were processed using the BacT/Alert system were younger (median, 64 vs 70 years; P = .003), had a higher proportion of HIV (9.03% vs 1.75%; P = .008) and a lower qSOFA (P = .003). There were no statistically significant differences in the most commonly identified bacterial species. TTP was shorter for BACTEC (median [interquartile range {IQR}], 12.5 [10-14] hours) compared with BacT/Alert (median [IQR], 17 [14-21] hours; P < .0001).

Conclusions

In this large prospective multi-centre study comparing the two blood culture systems among patients with severe manifestations of sepsis, and using a rigorous pre-analytical methodology, the BACTEC system yielded positive culture results 4.5 hours earlier than BacT/Alert. These results apply to commonly isolated bacteria. However, our study design did not allow direct comparison of TTP for unusual pathogens nor of clinical sensitivity between systems. More research is needed to determine the clinical implications of this finding.

847. The Effect of Antimicrobial Administration on Blood Culture Positivity in Patients with Severe Manifestations of Sepsis

Background

Current guidelines recommend obtaining blood cultures prior to antimicrobial therapy in patients with sepsis. Administering antimicrobials immediately without waiting for blood cultures could potentially decrease time to treatment and improve outcomes, but it is unclear the degree to which this strategy impacts diagnostic yield.

Methods

We performed a patient-level, single-arm, diagnostic trial. Seven urban emergency departments affiliated with academic medical centers across Canada and the United States participated in the study. Adults ≥18 years of age presenting to the emergency department with evidence of severe manifestations of sepsis, including a systolic blood pressure <90 mmHg and/or a serum lactate ≥4 mmol/L were included. Study participants had 2 sets of blood cultures drawn prior to and immediately following antimicrobial administration. The primary outcome was the difference in blood culture pathogen recovery rates before and after administration of antimicrobial therapy.

Results

Of the 3,164 participants screened, 325 were included in the study (mean age, 65.6 years; 63.0% men) and had repeat blood cultures drawn after the initiation of antimicrobial therapy (median time of 70 minutes, IQR 50 to 110 minutes). Pre-antimicrobial blood cultures were positive for one or more microbial pathogens in 102/325 (31.4%) patients. Fifty-four participants (52.9%) had matching blood culture results after initiation of antimicrobial treatment. The absolute difference in pathogen recovery rates was 14.5% ([95% CI 8.0 to 21.0%]; P < 0.0001) between pre- and post-antimicrobial blood cultures. Results were consistent in an analysis of the per-protocol population (absolute difference, 13.3% [95% CI 6.1 to 20.4%]; P < 0.0001). Including the results of other microbiological cultures done as part of routine care, microbial pathogens were recovered in 69 of 102 (67.7%) participants (absolute difference, 10.2% [95% CI 3.4 to 16.8%]; P < 0.0001).

Conclusion

Among patients with severe manifestations of sepsis, the administration of empiric antimicrobial therapy significantly reduces the yield of pathogen recovery when blood cultures are drawn shortly after treatment initiation.

Disclosures

All Authors: No reported Disclosures.

Blood Culture Results Before and After Antimicrobial Administration in Patients With Severe Manifestations of Sepsis: A Diagnostic Study

BACKGROUND

Administering antimicrobial agents before obtaining blood cultures could potentially decrease time to treatment and improve outcomes, but it is unclear how this strategy affects diagnostic sensitivity.

OBJECTIVE

To determine the sensitivity of blood cultures obtained shortly after initiation of antimicrobial therapy in patients with severe manifestations of sepsis.

DESIGN

Patient-level, single-group, diagnostic study. (ClinicalTrials.gov: NCT01867905).

SETTING

7 emergency departments in North America.

PARTICIPANTS

Adults with severe manifestations of sepsis, including systolic blood pressure less than 90 mm Hg or a serum lactate level of 4 mmol/L or more.

INTERVENTION

Blood cultures were obtained before and within 120 minutes after initiation of antimicrobial treatment.

MEASUREMENTS

Sensitivity of blood cultures obtained after initiation of antimicrobial therapy.

RESULTS

Of 3164 participants screened, 325 were included in the study (mean age, 65.6 years; 62.8% men) and had repeated blood cultures drawn after initiation of antimicrobial therapy (median time, 70 minutes [interquartile range, 50 to 110 minutes]). Preantimicrobial blood cultures were positive for 1 or more microbial pathogens in 102 of 325 (31.4%) patients. Postantimicrobial blood cultures were positive for 1 or more microbial pathogens in 63 of 325 (19.4%) patients. The absolute difference in the proportion of positive blood cultures between pre- and postantimicrobial testing was 12.0% (95% CI, 5.4% to 18.6%; P < 0.001). Sensitivity of postantimicrobial culture was 52.9% (CI, 42.8% to 62.9%). When the results of other microbiological cultures were included, microbial pathogens were found in 69 of 102 (67.6% [CI, 57.7% to 76.6%]) patients.

LIMITATION

Only a proportion of screened patients were recruited.

CONCLUSION

Among patients with severe manifestations of sepsis, initiation of empirical antimicrobial therapy significantly reduces the sensitivity of blood cultures drawn shortly after treatment initiation.

PRIMARY FUNDING SOURCE

Vancouver Coastal Health, St. Paul's Hospital Foundation Emergency Department Support Fund, the Fonds de recherche Santé-Québec, and the Maricopa Medical Foundation.

Stability of Biological Activity of Frozen β-lactams over Time as Assessed by Time-Lapsed Broth Microdilutions

To evaluate the antimicrobial agent's stability stored at -80 °C, six β-lactams (meropenem, ertapenem, imipenem, ceftriaxone, ceftazidime, and piperacillin-tazobactam) were studied using the broth microdilution (BMD). The minimum inhibitory concentration (MIC) remained accurate with the same amount of frozen drug for at least six months. Thereafter, there was a diminishing drug concentration due to instability. At this temperature, most β-lactams can be frozen as a stock concentration for up to six months without a significant loss in antibiotic activity.

Hepatitis B testing practices at a tertiary care centre and their associated costs: A retrospective analysis

Background

Hepatitis B is a viral infection requiring specific serologic testing to diagnose the stage of the disease. There are many tests which can be ordered in a variety of combinations. This study aimed to assess routine Hepatitis B screening practices in a tertiary care centre and determine the diagnostic and economic benefits of protocolized ordering.

Methods

We evaluated all measurements of Hepatitis B total core antibodies, core IgM antibodies, surface antibodies and surface antigens performed at our institution between January 1, 2015 and December 31, 2015. We also recorded secondary testing (envelope antigens and antibodies, and viral DNA). Costs were estimated using provincial insurance reimbursement values. Using the subset of patients who received complete testing, we developed a reflexive screening protocol to minimize costs while simultaneously improving diagnostic utility.

Results

30,335 hepatitis B tests were performed at an estimated total cost of $584,683. 53.9% of patients were screened with a single test. 29% of patients who received secondary testing had no evidence of exposure on primary testing. Using the protocol of initial testing of total core antibody and surface antibody with reflexive testing, we would save an estimated $181,632 (95% CI $154,201.90 –$208,910.50) per year while providing more complete information.

Interpretation

Screening practices for Hepatitis B are frequently inadequate to diagnose and stage the infection and often included unnecessary testing. Protocolization of Hepatitis B testing could limit this practice while resulting in significantly lower costs.

731. Investigating Clinical Factors Contributing to Continued Antibiotic Therapy in Patients with Viral Upper Respiratory Tract Infections

Background

It has previously been demonstrated that upwards of 50% of patients presenting to Emergency Departments with symptoms of an upper respiratory tract infection receive empirical antibiotics, and that even with a demonstrated viral infection, 70% of these patients are continued on antibiotics. However, the clinical and biochemical factors contributing to this continued therapy is unclear. This study assessed parameters that may impact antibiotic prescriptions in patients with a confirmed viral respiratory infection. Methods. Positive respiratory virus PCRs (RVPs) from nasopharyngeal aspirates performed on adult patients presenting to the McGill University Health Centre Emergency Departments and outpatient clinics over a period of 10 days during the peak of influenza season were included. For each patient, antibiotic administration pre- and post-PCR result were determined, as were the presence of leukocytosis, neutrophilia, an abnormal chest X-ray, and sepsis. Each parameter’s effect on antibiotic use was then determined. Results. During the study period, there were 123 positive RVPs included. These consisted of 34% Flu A, 43% Flu B, and 23% were a mixture of other common respiratory viruses. Antibiotics were administered in 38% of patients before the test was resulted and continued in 79% of these patients afterwards. There was no correlation between the presence of leukocytosis, neutrophilia, signs of sepsis or abnormalities on chest X-ray and continued antibiotic therapy. Conclusion. Despite identification of a respiratory virus infection, patients are routinely treated with antibiotics even without significant evidence of a bacterial process. The impact of testing for respiratory viruses in limiting antibiotic therapy could be improved by education and direct antibiotic stewardship interventions in this population.

Disclosures

All authors: No reported disclosures.

Daptomycin versus placebo as an adjunct to beta-lactam therapy in the treatment of Staphylococcus aureus bacteremia: study protocol for a randomized controlled trial

BACKGROUND

Staphylococcus aureus bacteremia is associated with significant morbidity and mortality. To treat this infection, the current standard of care includes intravenous anti-staphylococcal beta-lactam antibiotics and obtaining adequate source control. Combination therapy with an aminoglycoside or rifampin, despite early promise, can no longer be routinely recommended due to an absence of proven benefit and risk of harm. Daptomycin is a rapidly acting bactericidal antibiotic that is approved for the treatment of Staphylococcus aureus bacteremia as monotherapy but has not been shown to be superior to the current standard of care. As demonstrated in vitro, the addition of daptomycin to beta-lactam therapy may result in enhanced anti-staphylococcal activity. Our objective is to assess the efficacy and safety of prescribing the combination of daptomycin with cefazolin or cloxacillin for the treatment of methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia in adults. We hypothesize that adjunctive therapy with daptomycin will reduce the duration of bacteremia in this population.

METHODS

The DASH-RCT trial is a randomized, double blind, placebo-controlled trial designed per the Standard Protocol Items: Recommendation for Interventional Trials (SPIRIT) and Consolidated Standards of Reporting Trials (CONSORT) guidelines. We recruit adults with confirmed MSSA bacteremia, at the McGill University Health Center. Patients are eligible if they are 18 years or older, can receive cefazolin or cloxacillin monotherapy, and are enrolled within 72 h of the first blood culture being drawn. Exclusion criteria include anaphylaxis to study drugs, having polymicrobial bacteremia, anticipated hospital admission for < 5 days, and healthcare team refusal. While receiving standard of care, study patients are randomized to a 5-day course of adjunctive daptomycin or placebo. The trial began in December 2016 and is expected to end in December 2018, after recruiting an estimated 102 patients.

DISCUSSION

The DASH-RCT will compare the use of daptomycin as an adjunct to an anti-staphylococcal beta-lactam versus placebo in the treatment of MSSA bacteremia. We believe that a short course of dual therapy will result in earlier eradication of bacteremia and that subsequent research could evaluate effects on metastatic infection, relapse, and/or mortality. Ongoing issues in the trial include a delay between presentation of infection, enrollment in the trial, and the potential for unrecognized deep foci of infection at diagnosis.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02972983 . Registered on 25 November 2016. Trial protocol: http://individual.utoronto.ca/leet/dash/dashprotocol.pdf.