bluuebunny/crossref_metadata_2025_split huggingface dataset:
649. Clinical Implementation of a Rapid Susceptibility Testing Procedure, Directly From a Positive Blood Culture Using the Vitek®2 System on Gram Negative Rods
Authors: Henry Charma , Evans Dustin , Navas Daniel , Barker Arleen , Somyos Chonnapat , Rodriguez Melissa , Rahimzadeh Nahid , Silva Victoria , Carr Amy , Charles Angela , Alexander Jose 
Published: January 2021

Abstract

Background
The national average of identification and susceptibility for organisms isolated from positive blood culture to final susceptibility based on growth on solid media is 48 hours. The goal of this research was to prove that the Vitek®2 (bioMérieux, Inc.) system can provide an accurate and reliable susceptibility result directly from positive blood culture for Gram negative rods and reduce the turnaround time (TAT) from positive blood culture to the final susceptibility.

Methods
An FDA-modified validation procedure was performed on positive blood cultures directly from the bottle to the VITEK®2 System for susceptibility testing. The protocol tested and validated an aliquot of 50uL of blood directly from the positive bottle into 10 mL of saline (1:200). The solution was vortexed and 3mL were placed in the VITEK®2 test tube. This protocol was intended only for Gram negative rods using the AST-GN70, AST-GN81 & AST-GN801 cards. This protocol followed the CLSI M52 and M100 guidelines.

Results
515 organisms from clinical blood culture samples from July 2018 to October 2019 were evaluated. Organisms included, but were not limited to: E. coli, K. pneumoniae, Enterobacter spp., and P. aeruginosa, Proteus spp., Salmonella spp., Acinetobacter spp., and S. maltophilia. There were 5,201 drug/bug combinations. AdventHealth Orlando achieved an essential agreement of 99.32% (n=5,166), minor error 0.74% (n=39) major error 0.02% (n=1) and very major error 0.49% (n=2). A 100% agreement was achieved on detection of ESBL, CRE, and MDR organisms.

Conclusion
Rapid direct blood culture protocol using the VITEK®2 System and the AST-GN cards is accurate, reliable and can be performed with less than 1 minute hands-on time. The protocol can be implemented in any laboratory at no additional costs or modification where the current VITEK®2 AST-GN panels are in use. This protocol was clinically implemented at AdventHealth Orlando on July 15, 2019. Compared with the national average of 72 hours, the TAT obtained during this study was 23 hours from positive blood culture to final susceptibility, a significant reduction of 25 hours. The authors encourage bioMérieux Inc. to evaluate and explore the opportunity to expand the use of the VITEK®2 system for this application with the appropriate clinical trial.

Disclosures
All Authors: No reported disclosures
651. Comparative Analysis Between Bacterial And Fungal Malignant Otitis Externa
Authors: Hammami Fatma , Koubaa Makram , Chakroun Amal , Smaoui Fatma , Rekik Khaoula , Elleuch Emna , Marrakchi Chakib , Jemaa Mounir Ben 
Published: January 2021

Abstract

Background
Malignant otitis externa is a fatal infection of the external ear and temporal bone. Pseudomonas aeruginosa is the most common causative organism, while fungi are a rare cause of malignant otitis externa. We aimed to compare the clinical, therapeutic and evolutionary features between bacterial and fungal malignant otitis externa.

Methods
We conducted a retrospective study including all patients hospitalized for malignant otitis externa in the infectious diseases department between 2000 and 2018.

Results
Overall, we encountered 82 cases of malignant otitis externa, among which there were 54 cases (65.9%) of bacterial malignant otitis externa (BMO) and 28 cases (34.1%) of fungal malignant otitis externa (FMO). The males were predominant among BMO cases (57.4% vs 50%; p=0.5). Patients with FMO were significantly older (70±9 years vs 61±10 years; p&lt; 0.001) and had medical history of diabetes mellitus more frequently (96.4% vs 77.8%; p=0.03). The use of topical corticosteroids was significantly more reported among FMO cases (28.6% vs 5.6%; p=0.006). Otalgia (96.4% vs 81.5%), otorrhea (75% vs 66.7%) and cephalalgia (46.4% vs 42.6%) were the revealing symptoms among FMO and BMO, respectively, with no significant difference. Tenderness to palpation of the mastoid bone (64.3% vs 38.9%; p=0.02) and stenosis of the external auditory canal (92.9% vs 72.2%; p=0.02) were significantly more frequent among FMO cases. Complications were significantly more frequent among FMO cases (42.9% vs 9.3%; p&lt; 0.001). Treatment duration was significantly longer among FMO cases (70[40-90] days vs 45[34-75] days; p=0.03).

Conclusion
Our study showed that FMO affected more frequently the elderly and diabetic patients, when compared with BMO. Regardless of the causative agent, the clinical presentation was similar. However, the outcome was poor among FMO cases with the occurrence of complications, requiring a longer duration of treatment.

Disclosures
All Authors: No reported disclosures
652. Comparison of fosfomycin (FOF) activity and prevalence of subpopulations between Escherichia coli (EC) and Klebsiella pneumoniae (KP) during susceptibility testing
Authors: Anderson Jadyn C , Krueger Amanda R , Smith Elizabeth C , Bixby Morgan L , Brigman Hunter V , Hirsch Elizabeth B 
Published: January 2021

Abstract

Background
In the United States, interpretive criteria for FOF are established only for EC, yet those criteria are often extrapolated to KP. Recent studies have highlighted both inferior clinical outcomes after FOF treatment and difficulties in interpretation of inner colony subpopulations, the presence of which may affect clinical efficacy. We sought to compare FOF activity against EC and KP and to determine the prevalence of inner colony subpopulations following disk diffusion (DD) testing of the two species.

Methods
A convenience collection of 73 KP and 42 EC isolates from 3 U.S. institutions were included. Minimal inhibitory concentration (MIC) testing was performed in duplicate on separate days using agar dilution (AD) and DD as recommended by the Clinical and Laboratory Standards Institute guidelines, with application of EC susceptibility (≤ 64mg/L) breakpoints. The frequency and counts of inner colonies observed during DD testing was calculated, and colonies were subcultured for use in future studies.

Results
MIC50/90 values were 1/16 mg/L and 32/256 mg/L for EC and KP respectively. All EC isolates were considered susceptible and therefore categorical agreement was 100%. The majority of KP isolates were considered susceptible (83.6% with AD and 86.3% with DD) and categorical agreement between the methods was 84.9%. Inner colonies were observed during DD testing in 88.1% of EC isolates and 80.8% of KP isolates during at least one replicate, with 47.6% of EC isolates and 39.7% of KP isolates showing inner colony growth during both DD test replicates. More than 10 inner colonies were observed in 50% of EC isolates compared to 12.3% of KP isolates.

Conclusion
KP isolates demonstrated considerably higher FOF MIC values compared to EC, as evidenced by MIC50/90 values 4-5 dilutions higher than those for EC. The categorical agreement rate was higher among EC than KP, highlighting concerns regarding the practice of extrapolating FOF susceptibility breakpoints for EC to KP. The high frequency of inner colonies observed in DD for both species necessitates further studies to determine best practices for interpreting their relevance, fitness, and resistance in order to identify potential impacts to clinical efficacy of FOF.

Disclosures
Elizabeth B. Hirsch, PharmD, Merck (Grant/Research Support)Nabriva Therapeutics (Advisor or Review Panel member)
654. Core Antibiotic-Induced Transcriptional Signatures Reflect Susceptibility to All Members of an Antibiotic Class
Authors: Martinsen Melanie A , Bhattacharyya Roby P 
Published: January 2021

Abstract

Background
Current growth-based antibiotic susceptibility testing (AST) is too slow to guide key clinical decisions. We previously demonstrated a combined Genotypic and Phenotypic AST assay using RNA detection (GoPhAST-R) that can provide AST in &lt; 4h directly from blood culture, 24-36h faster than standard growth-based methods. GoPhAST-R quantifies specific mRNA expression signatures using the multiplexed hybridization RNA-detection platform, NanoString. After brief antibiotic exposure, susceptible cells become stressed, eliciting transcriptional changes that distinguish them from unharmed resistant cells. Here, we assess the generalizability of transcriptional signatures of susceptibility within an antibiotic class.

Methods
For Escherichia coli and Klebsiella pneumoniae, we assessed the ability of the top ten antibiotic-responsive genes previously identified for ciprofloxacin, gentamicin, and meropenem to predict susceptibility to two other fluoroquinolones (FQ), two other aminoglycosides (AG), and six other beta-lactams (BL), respectively, across 6-8 clinical isolates for each drug for a total of 184 pathogen-drug pairs. After standardized antibiotic exposure (60m for FQs and AGs, 120m for BLs, each at its CLSI breakpoint MIC), samples were mechanically lysed and used as input for NanoString assays as previously described (Bhattacharyya, Nat Med 2019).

Results
In both species, the top ten genes identified for AST of ciprofloxacin, gentamicin, and meropenem showed similar normalized fold-induction upon treatment with three FQs, three AGs, and seven BLs, respectively, allowing robust distinction of susceptible and resistant isolates (Fig 1).
Figure 1

Conclusion
We show that a shared set of genes optimized for AST of one antibiotic can predict susceptibility to all members of that drug class, consistent with a conserved core transcriptional response related to mechanism of action. We demonstrate this phenomenon for two common pathogens with propensity for multidrug resistance treated with multiple members of three major antibiotic classes in common clinical use. This unified set of genes for susceptibility prediction would streamline GoPhAST-R implementation, in turn facilitating efficient deployment of antibiotics and reducing unnecessary broad-spectrum use.

Disclosures
All Authors: No reported disclosures
657. Diagnostic Utility of Dedicated Fungal Blood Cultures for Diagnosis of Candidemia
Authors: Yang Bryant , Garner Omai , Ou Richard , Stanzione Nicholas 
Published: January 2021

Abstract

Background
Blood culture techniques have improved to the point where they are considered sensitive enough for detection of Candida. Expert guidelines clarifying the utility of use of dedicated fungal isolator cultures are lacking, and we wondered what utility, if any, they add for the diagnosis of candidemia.

Methods
All patients with cultures between March 2016-February 2020 positive for Candida were examined via manual chart review, noting time to positivity and time of initiation of antifungal therapy.

Results
We focused on cases of candidemia where a fungal culture was ordered and turned positive (59 out of the total 181 cases of candidemia). We eliminated an additional 10 cases where fungal cultures were sent while already on antifungal therapy or in patients already known to be fungemic, given our interest in de novo diagnoses. Another case was removed due to lack of clinical details, as the patient was discharged prior to culture results and managed at a different medical facility.
There were 14 cases with discordant growth (fungal culture positive, bacterial culture negative). One patient passed away prior to culture results, but in the remaining 13 cases, the fungal culture changed clinical management, in most cases by prompting initiation of antifungal therapy.
The remaining 36 cases involved with concordant growth between bacterial and fungal cultures. In 11 of those cases, the fungal culture isolated yeast 12 or more hours faster than its paired bacterial culture (average 40.7 +/- 26.6 hours). In 7 of these cases, the fungal culture changed management – in the remaining cases, the patient was already on empiric therapy.
Among all cultures sent in patients not receiving antifungals that isolated Candida, the overall time to positivity for fungal cultures was 37.2 +/- 13 hours, while bacterial cultures took 54 +/- 26.4 hours.
Fungal Culture Results

Conclusion
Fungal cultures changed management in 20/59 cases of candidemia (34%) either by making the diagnosis faster than a bacterial culture or making it outright. Given the morbidity and mortality associated with candidemia, rapid diagnosis is critically important. More specific guidelines optimizing how to best utilize fungal cultures to help standardize practice among clinicians will be critical going forward.

Disclosures
Omai Garner, PhD, D(ABMM), Beckman Coulter (Scientific Research Study Investigator)
660. Evaluation of Qvella’s FAST-Prep™ Liquid Colony™ for Early Antimicrobial Sensitivity Testing of Positive Blood Culture by Disk Diffusion Method
Authors: Novak-Weekley Susan M , Khine Aye Aye , Alavie Tino , Fernandez Namidha , Pandey Laxman , Talebpour Abdossamad 
Published: January 2021

Abstract

Background
Conventional antimicrobial susceptibility testing (AST) of microorganisms from positive blood cultures (PBC) can take ≥ 2 days. In order to improve the turnaround time for AST on a PBC, CLSI and EUCAST have made efforts to standardize procedures for disk diffusion (DD) direct from a PBC. Qvella Corporation (Richmond Hill, ON, Canada) has recently developed FAST-Prep, an automated centrifugal sample preparation system that rapidly delivers a Liquid Colony consisting of a purified, concentrated, viable cell suspension directly from a PBC. This study was performed to investigate the feasibility of DD AST off of a PBC using a FAST-Prep Liquid Colony.

Methods
Contrived PBC samples were prepared by spiking 6 species of Gram-positive and 4 species of Gram-negative bacteria (3-5 strains per species) into FA® Plus bottles and incubating in the BACT/ALERT® VIRTUO® System (bioMerieux, Durham, NC). After positivity, 3 mL of PBC was added to the FAST-Prep cartridge. After 20 minutes of processing in the FAST-Prep instrument, the Liquid Colony was removed from the cartridge and a 0.5 McFarland sample was prepared for DD AST. In parallel, the DD AST from a PBC was performed using 4 drops of PBC (CLSI direct method). Both methods were compared to conventional colony-based DD AST. After 16-18 hours of incubation zone diameters and S/I/R interpretations were determined. Categorical agreement (CA) and errors for both DD AST methods were calculated. In addition, colony plate counting was performed on 0.5 McFarland suspensions of Liquid Colony and the plate colony to determine biomass recovery and sample purity.

Results
CA for a FAST-Prep DD AST for Gram-positive and Gram-negative bacteria was 95.6% and 98.6%, respectively, compared to CA for CLSI DD AST of 77.2% and 81.9%, respectively. Biomass in the Liquid Colony was 7.2x108 and 1.2x109 CFU for Gram-positive and Gram-negative bacteria, respectively. Cell concentration in the 0.5 McFarland suspension of the Liquid Colony was 3.7x107 and 5.9x107 CFU/mL for Gram-positive and Gram-negative bacteria, respectively, which was similar to the concentration for the reference colony suspension.

Conclusion
The results support the potential role of FAST-Prep in providing a Liquid Colony for use in rapid AST.

Disclosures
Susan M. Novak-Weekley, PhD, D(ABMM), Qvella (Employee, Shareholder) Aye Aye Khine, PhD, Qvella (Employee, Shareholder) Tino Alavie, PhD, Qvella (Employee) Namidha Fernandez, MS, Qvella (Employee) Laxman Pandey, MS, Qvella (Employee) Abdossamad Talebpour, PhD, Qvella (Employee, Shareholder)
661. Futility of Bacterial Bone Marrow Cultures: Experience over a 19 Year Period
Authors: Kline Ahnika , Porterfield Harry , Zelazny A 
Published: January 2021

Abstract

Background
Bone marrow biopsies are often performed on patients with unclear diagnoses and cultures may be ordered for both routine bacterial, mycobacterial and fungal pathogens. They are performed in semi-sterile conditions and involve needle penetration through the skin, posing an increased risk of skin contamination. These cultures also require a substantial amount of laboratory personnel time.

Methods
Cultures collected from 2001-2020 were surveyed in the lab electronic record. We assessed the culture type (fungal, bacterial, mycobacterial), and the presence of pathogens and contaminants. An organism was deemed a contaminant if it was consistent with skin flora or listed as a contaminant in the report given to the physician. Organisms for which the role in bone marrow disease is unclear were included as possible pathogens. For questionable non-contaminant organisms, clinical significance was determined based on if patient was treated for the organism. For all bone marrow cultures, growth of the same organism within 1 month of the bone marrow specimen was surveyed to determine whether the organism would have been found by alternative methods.

Results
Of 483 bacterial bone marrow cultures, there were 110 (23%) positives, of which 76 (69%) were deemed contaminants. Twenty (18%) of the 76 contaminants grew in the routine bacterial culture. However, 49 (65%) contaminants grew in the AFB culture, of which 10 also grew in the bacterial culture. For the 34 non-contaminant organisms, 26 were determined to be clinically significant. Nineteen of the 26 had a matching culture (usually blood) growing the organism within 1 month. The majority of pathogens were mycobacteria (18 of the 34). Fungal organisms represented 5 cultures and 11 were bacterial. Of the 11 bacterial organisms, 1 was a Helicobacter species (grown in special media), and 4 had a matching positive blood culture. Only 4 (1% of 483) bacterial non-contaminants grew in the routine bacterial culture. Given an unknown number of true negatives, we can only conclude a positive predictive value (PPV) of 0.16 for routine bacterial cultures. Including AFB and fungal cultures, the PPV increased to 0.30.

Conclusion
Our findings indicate that routine bacterial bone marrow culture is unlikely to yield a novel result and is likely a poor use of lab resources.

Disclosures
All Authors: No reported disclosures
666. Microbial Cell-Free DNA Sequencing for Evaluation of Response to Antibiotic Therapy in Patients with Relapsed or Refractory Leukemia
Authors: Wolf Joshua , Goggin Kathryn , griffen Amanda , Kohler Christina , Allison Kim J , Inaba Yuki , Ahmed Asim A , Hollemon Desiree D , Brenner Abigail , Maron Gabriela , Maron Gabriela , Sun Yilun , Tang Li , Gawad Charles , Margolis Ellie 
Published: January 2021

Abstract

Background
In patients with bloodstream infection (BSI), true eradication of infection takes longer than blood culture clearance. Therefore, optimal treatment duration, especially in immunocompromised hosts, is unknown. A sensitive test of microbiological response to treatment could improve care by indicating a time for safe antibiotic discontinuation. Microbial cell-free DNA sequencing (mcfDNA-seq) is a sensitive predictor of BSI, and we hypothesize that it might also be useful to measure response to treatment.

Methods
Eligible participants were &lt; 25 years of age being treated for leukemia. Remnant plasma samples were collected as part of a prospective study (PREDSEQ), and underwent mcfDNA-seq by Karius Inc. in a CLIA/CAP-accredited laboratory. Pathogen DNA was reported in molecules per microliter (MPM). Testing was batched and blinded. Available samples from Day 1 through Day 7 after onset of bacterial BSI were included. We evaluated decay of the BSI pathogen DNA after initiation of effective antibiotic therapy, from the peak to last available sample, and compared episodes with slow (&lt; 0.5 log10 MPM/day) vs. rapid DNA decay.

Results
There were 13 evaluable BSI episodes in 9 participants; 7 had slow DNA decay. Persistence of bacteremia or fever ≥1 day after initiation of effective antibiotics occurred in 9/13 episodes (7/7 slow decay and 2/6 rapid decay; P = 0.02). Slow decay persisted beyond resolution of bacteremia and fever in 3/7 of these cases.
Figure 1. Pathogen DNA Concentration by mcfDNA-seq During Antibiotic Treatment of Bacteremia; Dashed line, blood culture positive; Red circle, last fever

Conclusion
In this small convenience sample of patients with leukemia, slow mcfDNA-seq DNA decay correlated with persistent fever or bacteremia. Post-BSI mcfDNA-seq monitoring should be investigated with the goal of decreasing inappropriate antibiotic therapy and preventing treatment failure.

Disclosures
Joshua Wolf, MBBS, PhD, FRACP, Karius inc (Grant/Research Support) Asim A. Ahmed, MD, Karius (Employee) Desiree D. Hollemon, MSN, MPH, Karius inc (Employee) Charles Gawad, MD PhD, Karius inc (Grant/Research Support)
668. Rapid Identification and Antimicrobial Susceptibility Testing of Gram-Negative Rod Bacteremia: Impact on Duration of Hospital Admission
Authors: Rogers Ralph , Tansarli Giannoula , Parente Diane , Brotherton Amy , Shah Rajeev , Cunha Cheston , Bobenchik April , Chapin Kimberle 
Published: January 2021

Abstract

Background
There are many emerging diagnostic technologies that provide rapid identification (ID) and antimicrobial susceptibility testing (AST) of blood cultures after initial microbial growth is detected. The clinical utility of having these results sooner than standard of care (SOC) ID/AST testing is less clear; one potential advantage would be shorter hospital admissions for those patients with less severe infections whose discharge planning is delayed while waiting for ID/AST results.

Methods
The Accelerate Pheno™ rapid ID/AST system (AP) was implemented in the clinical microbiology lab at two hospitals within our academic hospital system to run in parallel with our SOC ID/AST diagnostics for all blood cultures with Gram-negative rod (GNR) bacterial growth on initial Gram stain. Results of both diagnostic assays were uploaded to the medical record when available; our antimicrobial stewardship (AS) team discussed the AP results with clinical care teams during working hours. Length of stay (LOS) data was compared between a cohort with GNR bacteremia before and after the implementation of AP testing with AS review.

Results
There were 207 patients with GNR bacteremia admitted to the hospital during the first six months after implementation of AP testing with AS review (12/2019 – 05/2020). A historical cohort of 96 patients with GNR bacteremia (admitted 01/2018 – 08/2018) with SOC testing without AS review was used for comparison. Median LOS was 5.28 and 5.84 days for the AP and SOC cohorts, respectively; the distribution in the two groups differed significantly (Mann-Whitney U = 8728.5, p = 0.0446). There was also an increase in the percent of admissions shorter than 2 days between the AP and SOC cohorts (12.5% v. 5.2%, p = 0.024) [Figure1].
Figure 1

Conclusion
The use of a rapid ID/AST diagnostic technology with AS review may lead to shorter hospitalizations in select patient populations.

Disclosures
Kimberle Chapin, MD, genmark (Scientific Research Study Investigator)