bluuebunny/crossref_metadata_2025_split huggingface dataset:
637. Whole-Genome Sequencing (WGS) of Isolates from Resolving (RB) and Persistent (PB) Methicillin-Resistant Staphylococcus aureus Bacteremia
Authors: Sharma-Kuinkel Batu K , Medie Felix , Ruffin Felicia , Wattam Rebecca , Shukla Maulik , Davis James , Yeaman Michael , Fowler Vance G 
Published: October 2019

Abstract

Background
The basis for PB in MRSA is poorly understood. We tested the hypothesis that PB isolates will exhibit distinct genetic variation vs. resolving bacteremia (RB).

Methods
MRSA isolates from an existing cohort of prospectively enrolled patients with PB (n = 81) and RB (n = 81) were matched by sex, age, dialysis, diabetes mellitus, and presence of any implantable medical device. WGS was performed via MiSeq 2x150 runs (Illumina®) with a targeted depth of 150-fold at Duke Genome Sequencing Core (DUGSIM). The genome sequence was analyzed, assembled, and annotated in PATRIC.

Results
No genetic signature was associated with PB or RB isolates at the genome-wide significance level. Phylogenetic analysis separated the genomes into two distinct clades [Clade 1 (C1): 77 genomes; predominantly CC5; Clade 2 (C2): 74 genomes; predominantly CC8; Figure 1]. Most isolates in C1 genome carried SCC Mec type II (2A) vs. the SCC Mec type IV (2B) in C2. C1 and C2 had a total of 3602 (407 unique only to C1) and 3563 (368 unique only to C2) protein families, respectively, with 3195 families shared across the two groups. Out of the 407 unique C1 protein families, majority were not shared across all the genomes and only 28 were found in more than 40 of the genomes. A detailed look of 28 protein families showed that majority were found to be in 3 distinct genomic regions (R1—5.6 kb, 7 genes, also contains mecI; R2—18.2 kb; 16 genes; R3—6.3 kb, 6 genes, 2 predicted erythromycin resistance gene). Furthermore, 12 of C1 genomes lack these unique regions. Most of the genomes in C1 (Other than 12 genomes) carry genes responsible for erythromycin and clindamycin resistance. Out of the 368 protein families unique to C2, only 3 are widely shared (2 hypothetical proteins and 1 two-component transcriptional regulator. Patient characteristics were not associated with clade type.

Conclusion
The basis for the PB phenotype in patients with MRSA bacteremia is not due to sequence-based variation in the bacterial genome.

Disclosures
All authors: No reported disclosures.
655. Detection of Antibiotic Resistance Genes in Clinical Samples using T2 Magnetic Resonance
Authors: Snyder Jessica L , Manning Brendan , Shivers Robert , Gamero Daniel , Giese Heidi , Phung Nu , Chang Benjamin , Lapp Heather , Paggi Riccardo , Posteraro Brunella , Sanguinetti Maurizio , De Angelis Giulia , Mencacci Antonella , Lowery Thomas J 
Published: October 2019

Abstract

Background
Antibiotic-resistant bacteria are spread through selective pressure from the use of broad-spectrum empirical therapies, mobile genetic elements that pass resistance genes between species, and the inability to rapidly and appropriately respond to their presence. Resistance gene identification is often performed with post culture molecular diagnostic tests. The T2Resistance Panel, which detects methicillin resistance genes mecA/C; vancomycin resistance genes vanA/B; carbapenemases blaKPC, blaOXA-48,blaNDM, blaVIM, and blaIMP; AmpC β-lactamases blaCMY and blaDHA; and extended-spectrum β-lactamases blaCTX-M directly from patient blood samples, is based on T2 magnetic resonance (T2MR), an FDA-cleared technology with demonstrated high sensitivity and specificity for culture-independent bacterial and fungal species identification. Here we report the clinical performance of T2MR detection of resistance genes directly from patient blood samples.

Methods
Patients with a clinical diagnosis of sepsis and an order for blood culture (BC) were enrolled in the study at two sites. BCs were managed using standard procedures and MALDI-TOF for species identification. Resistance testing with the T2MR assay was performed on a direct patient draw and compared with diagnostic test results from concurrent BC specimen and BC specimen taken at other points in time. The potential impact on therapy was evaluated through patient chart review.

Results
T2MR detected the same resistance genes as detected by post culture diagnostics in 100% of samples from concurrent blood draws. Discordant results occurred when T2MR was taken ≥48 hours after BC for patients on antimicrobial therapy. The average time to positive result was 5.9 hours with T2MR vs. 30.6 hours with post-culture molecular testing.

Conclusion
The T2Resistance Panel detected antibiotic resistance genes in clinical samples and displayed agreement with post culture genetic testing. T2MR results were achieved faster than culture-dependent diagnostic testing results and may allow for an earlier change from empiric to directed therapy. The use of culture-independent diagnostics like T2MR could enable a quicker response to antibiotic-resistant organisms for individual patients and developing outbreaks.

Disclosures
All authors: No reported disclosures.
669. Twelve-Month Durability of Microbiota-Based Therapy RBX2660 for Prevention of Recurrent Clostridium difficile Infection
Authors: Jones Courtney , Mische Sarah , Blount Ken , Shannon Bill 
Published: October 2019

Abstract

Background
Recurrent Clostridium difficile infections (rCDI) are a public health threat with insufficient treatment options at present. Two Phase 2 clinical studies have reported the efficacy of RBX2660, a standardized, stabilized microbiota-based drug, in preventing rCDI. For one of these trials, we report herein the durability of clinical response (lack of CDI recurrence) and microbiome restoration to 12 months after RBX2660 treatment.

Methods
Data were drawn from an interim analysis of a multicenter, open-label Phase 2 study in which participants with multi-recurrent rCDI received up to 2 doses of RBX2660 delivered via enema 7 days apart; this analysis includes data to 12 months after treatment, with follow-up ongoing. Efficacy was defined as the absence of CDI recurrence to 56 days after the last dose; and durability is defined as a continued lack of reported recurrence. Participant stool samples collected prior to and at 1, 7, 30, 60 days and 6 and 12 months after treatment were sequenced using a shallow shotgun method, with only treatment responders reported herein. Operational taxonomic unit (OTU) data were used to calculate relative abundance at the class level and Microbiome Health Indices.

Results
This study included 149 RBX2660-treated participants and 110 historical control patients, in the United States and Canada. As previously reported, the efficacy of RBX2660 in preventing rCDI (79.9%; 119/149) was higher than CDI-free rates in the historical control group (51.8%, 57/110; P < 0.001). Of 109 participants who had a 6-month follow-up, 97.2% (106/109) remained CDI-free, and no new CDI recurrences were reported at 12 months. Among treatment responders, the microbiome composition was restored after treatment to predominance by Bacteroidia- and Clostridia-class bacteria, and these compositions remained stable to 12 months after treatment among participants who provided samples.

Conclusion
RBX2660, a microbiota-based drug, was efficacious for preventing rCDI, with clinical and microbiome restoration durability to at least 12 months after treatment. The follow-up of efficacy, safety, and microbiome restoration are ongoing.

Disclosures
All authors: No reported disclosures.
670. VRE Clearance in Patients with Recurrent Clostridium difficile Infection Following Treatment with Microbiota-Based Drug RBX2660
Authors: Hau Heidi , Mische Sarah , Klein Sarah , Blount Ken 
Published: October 2019

Abstract

Background
Vancomycin-resistant Enterococcus (VRE) infection is frequently associated with immunocompromised and critically ill patients. VRE carriers are at increased risk for infection due to VRE colonization and they pose a risk as a transmission source. VRE infection and Clostridium difficile infection (CDI) share common risk factors, including disruption of the intestinal microbiome. Thus, therapeutic approaches that decolonize VRE would be valuable. Herein, we report on stool VRE clearance in a cohort analysis from a Phase 2 open-label study of RBX2660, standardized microbiota-based drug, for recurrent CDI.

Methods
This prospective, multicenter, open-label Phase 2 study enrolled subjects with recurrent CDI. Participants received up to 2 doses of RBX2660 delivered via enema with doses 7 days apart. Patients were requested to voluntarily submit stool samples at baseline and at 7, 30 and 60 days, 6, 12, and 24 months after the last administration of RBX2660. Stool samples were tested for VRE using bile esculin azide agar with 6 µg/mL vancomycin and gram staining. Vancomycin resistance was confirmed via blood agar and etest.

Results
Stool samples were available for 143 patients. Twenty-one patients were VRE-positive at the first test (baseline or 7 day). Of the 19 VRE-positive patients that provided additional samples at later timepoints, 18 (94.7%) converted to negative as of the last available follow-up (30 or 60 days and 6, 12, or 24 months). The remaining patient remained positive at all follow-ups.

Conclusion
This cohort analysis of VRE-positive patients within an rCDI population provides additional support that microbiota-based formulations, such as RBX2660, may have additional benefit beyond reducing the recurrence of CDI. Additional study is needed to confirm the role of microbiome restoration on VRE clearance.

Disclosures
All authors: No reported disclosures
671. Impact of Dose-Administration Strategies of the Antistaphylococcal Lysin Exebacase, (CF-301), in Addition to Daptomycin (DAP) in an Experimental Infective Endocarditis (IE) Model due to Methicillin-Resistant Staphylococcus aureus (MRSA)
Authors: Xiong Yan , Abdelhady Wessam , Li Liang , Schuch Raymond , Cassino Cara , Lehoux Dario , Bayer Arnold 
Published: October 2019

Abstract

Background
MRSA infections, especially involving the endovascular system (e.g., IE), are associated with unacceptably high morbidity and mortality rates. The use of bacteriophage-derived lysin, which acts as direct lytic agents, represents a novel adjunctive approach against virulent Gram-positive bacteria, such as MRSA. The current study examined the efficacy of DAP alone or DAP plus CF-301administered on a single day using various dosing regimens, in a rabbit model of MRSA IE.

Methods
Aortic valve IE due to MRSA strain MW2 was induced by the IV administration of ~1 × 105–2 × 105 cfu in aortic-catheterized rabbits. At 24-hour post-infection, animals were randomized into one of the 13 groups: (1) vehicle controls given once daily (QD); 2–13) DAP alone (at 4 mg/kg iv QD × 4d; this dose yields significant but modest clearance of MRSA in experimental IE); DAP + CF-301 (given as an IV dose on the first day of DAP treatment only by 5–10 min slow bolus at (mg/kg): 0.70 QD, 0.35 Q12h, 0.23 Q8h, 0.35 QD, 0.175 Q12h, 0.117 Q8h, 0.09 QD, 0.045 Q12h, 0.03 Q8h, 0.06 QD, 0.03 Q12h or 0.03 QD. At 24 hours after the last DAP dose, three target organs were quantitatively cultured (cardiac vegetations; kidneys and spleen). Data for each organ were calculated as mean log10 cfu/g of tissue (±SD).

Results
Treatment with DAP alone caused ~2–3 log10 cfu/g reduction in MRSA densities in all three target tissues vs. vehicle controls. All CF-301 doses given in addition to DAP, even at the lowest CF-301 dose (0.03 mg/kg), significantly reduced MRSA densities further in all target tissues vs. DAP alone (~3 log10 cfu/g) and vehicle control groups (~6 log10 cfu/g). In general, DAP plus CF-301 given as a single dose trended toward better microbiologic efficacy than CF-301 given at Q12h or Q8h, although this difference was not statistically significant.

Conclusion
These results demonstrate that CF-301, given at multiple dose strategies and at different dose regimens, in addition to sublethal DAP, had significant efficacy in further decreasing MRSA densities in relevant target tissues in the IE model (vs. DAP alone and untreated controls). DAP plus a single dose of CF-301 trended to better efficacy than when it was administered in fractionated dose-strategies.

Disclosures
All authors: No reported disclosures.
682. In Vivo Pharmacodynamics of VNRX-7145 in the Neutropenic Murine Thigh Infection Model When Administered in Combination with Humanized Exposures of Twice Daily Ceftibuten (CTB) Against Serine β-Lactamase-Producing Enterobacteriaceae (SBL-EB)
Authors: Avery Lindsay M , Abdelraouf Kamilia , Nicolau David P 
Published: October 2019

Abstract

Background
There is a pressing need for development of oral antibiotics with activity against SBL-EB, particularly carbapenemase-producers, for use in the community or as step-down therapy for complicated urinary tract infection. VNRX-7145 is a novel boronic acid-based SBL inhibitor with no intrinsic activity that was designed as an orally bioavailable prodrug. The active moiety (VNRX-5236) is known to restore in vitro susceptibility to (CTB), an oral cephalosporin, among CTB-resistant SBL-EB.

Methods
CTB-resistant SBL-EB (N = 21) with CTB MICs ≥32 µg/mL and CTB/VNRX-5236 MIC range 0.12–2 µg/mL (VNRX-5236 fixed at 4 µg/mL) were evaluated. Carbapenemases were produced by 9 strains (4 OXA, 5 KPC). Bacterial suspensions (~107 CFU/mL) were used to inoculate the thighs of neutropenic mice. A human-simulated regimen of ceftibuten (CTB HSR) equivalent to a 400 mg q12h dosage was developed in infected mice. In dose ranging studies, groups of 3 animals each received the CTB HSR as monotherapy or combined with escalating VNRX-5236 exposures (CTB:VNRX-5236 dose ratios ranging from 10:1 to 1:4). Efficacy was assessed as the change in log10 CFU/thigh at 24 hours from 0 hour burden. With previous in vivo dose fractionation studies indicating the free area under the VNRX-5236 concentration–time curve to MIC ratio (fAUC0-24/MIC) as the PK/PD driver of efficacy, the Hill equation was used to estimate the magnitude required to achieve a static endpoint.

Results
Compared with 0 hour controls (mean log10 CFU/thigh, 5.7 ± 0.3), the bacterial burden for all isolates increased in saline-dosed controls and CTB HSR groups by 3.1 ± 0.8 and 2.5 ± 0.8 log10 CFU/thigh, respectively. The addition of VNRX-5236 resulted in bacterial stasis in 20/21 strains; the mean reduction in bacterial burden with the 1:1 CTB:VNRX-5236 dose ratio was −0.2 ± 0.7 log10 CFU/thigh. A composite assessment of exposure-responses indicated a fAUC0-24/MIC of 9.0 (R2 = 0.70) was associated with stasis.

Conclusion
Against CTB-resistant SBL-EB, inclusive of OXA-48- and KPC-producing strains, VNRX-5236 potentiated the in vivo activity of the CTB human-simulated exposure. The identified fAUC0-24/MIC target associated with bacterial stasis should be considered when selecting VNRX-7145 doses for clinical studies.

Disclosures
All authors: No reported disclosures.
685. An In Vitro Investigation of WCK 5222 (Cefepime/Zidebactam) and Currently Available Combination Antibiotic Regimens Against Enterobacteriaceae That Co-express Serine-β-Lactamase (SBL) and Metallo-β-Lactamase (MBL) Enzymes
Authors: Avery Lindsay M , Mullane Elias M , Nicolau David P 
Published: October 2019

Abstract

Background
Carbapenem-resistant Enterobacteriaceae (CRE) that simultaneously harbor SBLs and MBLs may demonstrate pan-drug resistance. Current therapeutic options include combinations of aztreonam (ATM), which is resistant to hydrolysis by MBLs, plus ceftazidime/avibactam (CZA) or meropenem/vaborbactam (M/V) for coverage of relevant SBLs. However, these selections add a level of complexity to clinical management compared with administration of a single antibiotic as monotherapy.

Methods
Minimum inhibitory concentrations (MICs) of WCK 5222 (cefepime/zidebactam), ATM, CZA, and M/V were determined with Liofilchem MIC Test Strips against SBL- and MBL-positive CRE (N = 15). The gradient diffusion strip (GDS) cross method was used to assess the activities of CZA+ATM and M/V+ATM. Additive interactions as defined by fractional inhibitory concentration indices ≤ 1 would be predicted based upon the known genotypic profiles; thus, the relative activities of the combination regimens were compared with the “zone of hope” (ZOH) test. The size of the ZOH (the zone of inhibited growth) was quantitated by multiplying the observed length of inhibited growth (in mm) adjacent to each GDS from the point of intersection. The Mann–Whitney rank-sum test was used to assess differences.

Results
All isolates (N = 15) contained one MBL and ≥1 SBL, and were resistant to ATM, CZA, and M/V with the exception of one isolate intermediate to M/V (MIC=8 mg/L). The WCK 5222 MIC50 (range) was 1 (0.19–2) mg/L. The median (interquartile range) ZOH product for CZA+ATM and M/V+ATM was 75.4 (62.8–93.7) and 23.5 (14.1–60.4), respectively (P = 0.002). In strains that produced OXA-type carbapenemases (n = 6), the median ZOH product for CZA+ATM and M/V+ATM was 78.1 and 20.7, respectively (P = 0.004). In the remaining 9 strains with a single carbapenemase (i.e., the MBL),the median ZOH product for CZA+ATM and M/V+ATM was 73.8 and 25.6, respectively (P = 0.052).

Conclusion
WCK 5222 displayed potent in vitro activity against SBL- and MBL-positive CRE, warranting further pre-clinical in vivo evaluation as a monotherapy option. When considering the co-expression of SBL and MBL, CZA+ATM appears to offer enhanced coverage compared with M/V+ATM.

Disclosures
All authors: No reported disclosures.
689. Therapeutic Efficacy of CB-012, a Novel Cloudbreak Antiviral Fc-Conjugate (AVC) in Lethal Mouse Models of Influenza A (H1N1) and Influenza B (Victoria)
Authors: Levin James , Borchardt Allen , Lam Thanh , Jiang Wanlong , Chen Zhi-Yong , Fortier Joanne , Akers-Rodriguez Suzanne , Amundson Karin , Donatelli Joanna , Döhrmann Simon , Cole Jason , Tari Les 
Published: October 2019

Abstract

Background
In 2018, the World Health Organization estimated up to 650,000 influenza-related respiratory deaths occur annually. Cidara therapeutics is developing a novel class of potent, long-acting antiviral Fc-conjugates (AVCs) against influenza that in a single molecule combine a surface-acting antiviral agent with the Fc domain of a human IgG1 antibody. AVCs function by inhibiting viral replication while simultaneously engaging the immune system, providing a multimodal mechanism of action. Here we present efficacy data on an AVC development candidate against influenza A and B.

Methods
Efficacy studies were conducted in female BALB/c mice (6–8 weeks) challenged intranasally with 3x the LD95 of influenza A/Puerto Rico/8/1934 (H1N1) or B/Malaysia/2506/04. CB-012 or CB-012b (CB-012 with slightly modified Fc) was administered as a single intravenous (IV) dose 2 hours after challenge. Oseltamivir was dosed orally, twice daily for 5 days in the influenza A study. Vehicle and appropriate Fc controls were included. Body weights (BW) and mortality were monitored for 2 weeks; animals with 20% BW loss, or moribund, were scored as a death.

Results
In an initial study of CB-012 against influenza A, a single IV dose of 0.4 mg/kg was fully protective and statistically significant compared with the Fc control (P = 0.0027). In contrast, mice treated with oseltamivir at 5 mg/kg twice daily for 5 days were not protected; only the higher 20 mg/kg dose was fully protective. Importantly, mice treated with CB-012 (0.4 mg/kg) showed a transient BW loss of 1% compared with 14% in mice of the oseltamivir (20 mg/kg) group, although treatment was initiated at the same time. In a second study against influenza B, CB-012b was fully protective with a single IV dose at 0.3 mg/kg (P = 0.0027). In contrast, vehicle and Fc control groups reached mortality by day 6. BW loss in the CB-012b 0.3 mg/kg group was transient and <4% overall during the study.

Conclusion
The novel AVCs CB-012 and CB-012b demonstrated robust efficacy in multiple influenza models. In conjunction with previous findings against influenza A (H3N2), the data on CB-012 support its potential as a candidate against seasonal influenza. The continued development of CB-012 for the prevention and treatment of influenza is warranted.

Disclosures
All authors: No reported disclosures.
698. In vitro Activity of a New Generation Oxopyrazole Antibiotic Against Multidrug-Resistant Gram-Negative Bacilli
Authors: Goldberg Joel , Bethel Christopher , Hujer Andrea M , Hujer Kristine , Marshall Steven , Papp-Wallace Krisztina M , Perez Federico , Spencer Elizabeth , Hoyer Denton , Plummer Mark , Bonomo Robert A 
Published: October 2019

Abstract

Background
Multidrug-resistant Gram-negative bacilli (MDRGNB) are emerging as a challenging cause of hospital-acquired infections and represent a critical need for innovative antibacterial development. New oxopyrazole agents targeting penicillin-binding proteins (PBPs) based on a non-β-lactam core and incorporating a siderophore moiety (Figure 1) which facilitates transport to the periplasm are being developed that show promise against Gram-negative organisms including multidrug-resistant strains of E. coli, K. pneumoniae and P. aeruginosa.

Methods
YU253434, an example of this new class of antibacterials, was investigated in vitro. Minimum inhibitory concentrations (MICs) were determined by broth microdilution against a representative panel comprising 15 strains each of E. coli, K. pneumoniae and P. aeruginosa, which contain extended-spectrum β-lactamase (ESBL) and/or carbapenemases genes.All studies were performed according to current Clinical & Laboratory Standards Institute (CLSI) guidelines using iron-depleted media. Ceftazidime breakpoints were arbitrability chosen as a reference for YU253434 (susceptibilities ≤4 μg/mL for Enterobacteriaceae and ≤8 μg/mL for P. aeruginosa).

Results
MIC testing (Figures 2–4) against E. coli showed 11 strains were YU253434 susceptible (compared with 6 for ceftazidime, and 3 for imipenem); against K. pneumoniae 13 strains were YU253434 susceptible (compared with 2 for ceftazidime and 6 for imipenem); against P. aeruginosa 10 strains were YU253434 susceptible (compared with 0 for both ceftazidime and imipenem). There appeared to be no correlation between YU253434 resistance and the presence of specific lactamase genes.

Conclusion
YU253434, a new generation oxopyrazole antibiotic, demonstrated promising in vitro potency against a panel of E. coli, K. pneumonia, and P. aeruginosa strains which contain ESBL and/or carbapenemases genes.

Disclosures
All authors: No reported disclosures.