bluuebunny/crossref_metadata_2025_split huggingface dataset:
272. Dissecting Host-Commensal Interactions During Early Life to Identify Mechanisms of Protection Against Autoimmune Diabetes
Authors: Grimes Logan , Flores Julia , Lubin J B , Green Jamal , Silverman Michael 
Published: November 2023

Abstract

Background
Major Histocompatibility Complex (MHC) and Human Leukocyte Antigen (HLA) loci have strong genetic linkage with type 1 diabetes (T1D) in mice and humans, respectively. The diabetes-prone non-obese diabetic (NOD) strain of mice have a unique MHC-II locus with a distinct MHC-II A molecule (Ag7) and lack expression of the MHC-II E molecule. Expression of this MHC-II A molecule is associated with development of T1D, whereas transgenic restoration of the MHC-II E molecule dominantly protects against T1D. The Silverman laboratory recently demonstrated that MHC-II E molecule expression selects for a diabetes-protective intestinal microbiota in early life though a key knowledge gap remains: how do these two factors — MHC-II molecules and commensal microbiota — work together during a critical early-life period of microbiome and immune system ontogeny to prevent T1D? To address this question, the Silverman laboratory developed a gnotobiotic mouse model by designing a microbial community consisting of 9 intestinal microbes cultured from these diabetes-protected (Ea16/NOD) mice – called “PedsCom”. This gnotobiotic model allows for mechanistic, well-controlled studies of interactions between commensal microbes and the developing immune system.

Methods
We used flow cytometry to sort commensal bacteria from PedsCom-colonized NOD and Ea16/NOD mice into IgA-coated and IgA-uncoated populations. We employed species-specific multiplex qPCR to quantify relative abundance of each PedsCom microbe in these sorted populations.

Results
Two microbes, K. cowanii and L. murinus, were preferentially IgA bound in both NOD and Ea16/NOD mice. L. johnsonii, A. caccae, and S. xylosus were preferentially IgA bound only in the presence of MHC-II E molecule expression. Many of the highly IgA coated microbes (K. cowanii, L. murinus, L, johnsonii, and A. caccae) translocate to the mesenteric lymph nodes.
Conclusion: We propose that MHC-II expression facilitates specific mucosal IgA responses, that MHC-II E expression allows for additional epitope recognition amongst PedsCom members which may potentiate this effect, and that preferential IgA coating may promote contact with mucosa-associated lymphoid tissues as early steps in tolerogenic immune system ontogeny that protects against development of T1D.

Disclosures
All Authors: No reported disclosures
278. Effects of polymyxin B direct hemoperfusion by measurement of outer membrane vesicles in patients with septic shock
Authors: Min Jo Kyeong 
Published: November 2023

Abstract

Background
Sepsis is one of the most common reasons for admission to the intensive care unit, and its incidence continues to increase. However, the precise mechanism of sepsis has not yet been fully elucidated. Outer membrane vesicles (OMVs) present in the outer membrane of bacteria have been speculated to be one of the causes of sepsis. Direct hemoperfusion with polymyxin B-immobilized fiber (PMX-DHP) can be used as a means to remove OMVs. This study evaluated whether the use of PMX-DHP affects bacterial distribution.

Methods
A total of 30 critically ill patients with severe septic shock were enrolled from intensive care unit of Haeundae Paik hospital. Plasma and urine samples were collected before and after the use of PMX-DHP. Sequencing-based metagenome analysis of the microbiome was performed, and changes in the distribution of various bacteria before and after the use of PMX-DHP were identified.

Results
A total of 30 patients were enrolled. Figure 1 shows the changes in the distribution of bacteria in plasma before and after the use of PMX-DHP. The only strain that showed a statistically significant difference in the pre-mean and post-mean values in this distribution was Bradyrhizobium (0.0152 →0.0000, p=0.0255, Figure 2). Figure 3 shows the changes in the distribution of bacteria in urine before and after the use of PMX-DHP. No bacteria showed a statistically significant difference in distribution before and after the use of PMX-DHP in this distribution.
Figure 1
Distribution of bacteria in plasma before and after the use of PMX-DHP
Figure 2
Changes in the distribution of Bradyrhizobium in plasma
Figure 3
Distribution of bacteria in urine before and after the use of PMX-DHP

Conclusion
Bradyrhizobium was the only strain that showed a statistically significant decrease in the amount of outer membrane vesicles (OMVs) in plasma through hemoperfusion using PMX-DHP.

Disclosures
All Authors: No reported disclosures
282. Resistance to caspase-1 dependent pyroptosis of hypervirulent K. pneumoniae
Authors: ah Kim Hyun , Hyun Miri , Lee Jiyeon , Kyung Kim Jin , baek wonki 
Published: November 2023

Abstract

Background
Hypervirulent K. pneumoniae(Hv Kp) has emerged as a clinically significant global pathogen in the last decade. However, the host immune responses of the macrophages during hvKp infection are largely unknown. In the present study, we aimed to compare the cytotoxic effects of hvKp and classical K. pneumoniae (cKp) in murine macrophages.

Methods
Bacterial strains are obtained from clinical samples who infected by K. pneumoniae. The rmpA and iutA positive strains with mucoid phenotype were defined as hypervirulent K. pneumoniae. Raw 264.7 cell and BMDM(bone marrow derived macrophage) cell were used for experiments. Wild-type C57BL/6 female mice and Casp1-/- female mice (age, 7–9 weeks) were used. Cytotoxicity after 4 hours of infection, MTS and LDH release was measured. FACS scan after PI dyed was performed for cell cycle analysis and cytotoxicity each MOI(Multiplicity of infection) concentration. Western blot analysis of caspase-1 and caspase-1 inhibitor were used. IL-1β was tested with ELISA.

Results
We found that the activation of caspase-1 (Casp1)-dependent pyroptosis was higher in cKp-infected macrophages compared with that in hvKp-infected macrophages. In caspase-1 deficiency macrophages, pyroptosis diminished during infection. Both hvKp and cKp strains led to nucleotide-binding and oligomerization domain-like receptor protein 3 (NLRP3) inflammasome formation and lysosomal cathepsin B activation, thus resulting in pyroptosis. Compared with the cKp strain, the hvKp strain inhibited these phenomena in murine macrophages.Figure 1.HvKp and cKp strains induce pyroptotic cell death in the RAW264.7 murine macrophage cell line.Figure 2.BMDMs were differentiated from WT and Casp1-/- mice and infected with the hvKp or cKp strains.

Conclusion
In this study, compared to classical strains, it was confirmed that cells infected with hv Kp survived without apoptosis. HvKp infection resulted in different levels of pyroptosis via the activation of cathepsin B-NLRP3-caspase-1 in murine macrophage. Therefore, the manipulation of pyroptotic cell death is a potential target for host response during hvKp infection in macrophages.

Disclosures
All Authors: No reported disclosures
284. Age-related differences in B-cell response during Clostridioides difficile infection in mice
Authors: Kumar Archit , O’Brien Martin , Nguyen Nhu , Vendrov Kimberly , Bergin Ingrid L , Young Vincent B , Yung Raymond 
Published: November 2023

Abstract

Background
Clostridioides difficile (C. difficile) infection (CDI) is a leading cause of nosocomial infection that can range from mild diarrhea to life threatening pseudomembranous colitis and death. Aging as well as defects in the host immune response including failure to develop antibody response against C. difficile antigens increases the risk of bacterial colonization, hospitalization, mortality and developing recurrent CDI. The present study aimed to investigate the differences in the B cell response between young and aged C. difficile infected mice.

Methods
C57BL/6 mice were rendered susceptible to CDI via the administration of oral cefoperazone for 10 days and then the mice were challenged with 103 spores of C. difficile R20291 strain (Figure 1). The young (3-4 months) and aged (22-24 months) mice were euthanized at 14 days post infection (dpi). The germinal center response and IgA+ antibody-secreting cells (ASCs) were studied using multicolor flow cytometry.

Results
C. difficile infected aged mice exhibited greater weight loss at 4 dpi compared to young C. difficile infected mice. The gut germinal center response studied at 14 dpi showed mild changes in T follicular helper cells (CXCR5+PD-1+ of CD4+) and germinal center B cells (GL7+CD95+ of CD19+B200+) of young C. difficile infected mice, whereas the response was dampened in the aged C. difficile infected mice (Figure 2). Further, at 14 dpi ASCs (CD138+CD98+) were seen in the lamina propria of the cecum and colon of the C. difficile infected mice, but the frequencies of CD138+CD98+ ASCs as well as IgA+ ASCs were significantly lower in the C. difficile infected aged mice compare to young mice (Figure 3).

Conclusion
The defect in B cell response during CDI may be responsible for more severe infection and recurrent CDI among aged individual compared to young individuals. It remains to be seen if age-related changes impact antibody production and whether the antibody production during primary CDI provides long-term immunity.

Disclosures
Vincent B. Young, MD, PhD, ASM: Senior Editor for mSphere Journal|Debiopharm: Consultant|mSphere: Senior Editor|Vendanta Biosciences: Consultant
289. Evaluation of Aztreonam-Avibactam In Vitro Activity Against VIM and GES β-lactamase Producing, Carbapenem-Resistant Pseudomonas aeruginosa Collected from Contaminated Artificial Tear Products
Authors: Lin Lynn-Yao , Debabov Dmitri 
Published: November 2023

Abstract

Background
A rare strain of extensively drug-resistant Pseudomonas aeruginosa was identified from contaminated artificial tear products that caused outbreak across 16 US states in March 2023. The strain carries Verona integron-encoded metallo-β-lactamase (VIM) and Guiana-Extended Spectrum-β-Lactamase (GES), a combination not previously identified in the US. Aztreonam (ATM) is a monobactam that is stable against hydrolysis by MBLs, and avibactam (AVI) inhibits class A, C, and some D β-lactamases. ATM-AVI is currently in development for treatment of infections caused by drug-resistant Gram-negative pathogens, especially those co-producing MBLs and other β-lactamases. This study evaluated in vitro activity of ATM-AVI against VIM and GES producing carbapenem-resistant P. aeruginosa (VIM-GES-CRPA) isolates acquired from CDC AR Bank.

Methods
Three VIM-GES-CRPA clinical isolates acquired from CDC AR Bank were tested for susceptibility to ATM and ATM-AVI (fixed concentration of 4 mg/L AVI) by broth microdilution (BMD). The isolates were tested concurrently by disk diffusion method using ATM-AVI 30-20 µg disks manufactured by BD Biosciences (BD) and Mast Group (Mast), as well as cefiderocol and ATM disks by Hardy diagnostics (Hardy) and by ATM-AVI E-test strips by Liofilchem, Inc. β-lactam/β-lactamase inhibitors (BL/BLI) were tested by BMD. All tests were interpreted using CLSI 2023 breakpoints. Tentative ATM-AVI pharmacokinetic/pharmacodynamic (PK/PD) susceptible MIC breakpoints of ≤ 8 mg/L (BMD, E-test) or ≥ 23 mm (disk diffusion) were applied for comparison purposes.

Results
The MIC values of ATM-AVI by BMD were in the range of 4-8 mg/L and correlated with the values measured by ATM-AVI E-test (3-8 mg/L), demonstrating in vitro activity against VIM-GES-CRPA. ATM-AVI inhibition zone diameters measured by both BD and Mast discs were in the range of 27-28 mm. The isolates were shown to be resistant to ATM alone, ceftazidime/avibactam, ceftolozane/tazobactam and imipenem/relebactam, but susceptible to cefiderocol.

Conclusion
Based on proposed PK/PD breakpoints, all tested isolates of VIM-GES-CRPA were susceptible to ATM-AVI. ATM-AVI demonstrated in vitro activity against these extensively drug-resistant P. aeruginosa isolated from contaminated artificial tear products.

Disclosures
Lynn-Yao Lin, M.S. Molecular Biotechnology, Abbvie Inc: Employee of Abbvie that participated in design, study conduct, financial support, interpretation of data, review, and approval of the publication Dmitri Debabov, PhD. Molecular biology, Abbvie Inc.: Employee of Abbvie that participated in design, study conduct, financial support, interpretation of data, review, and approval of the publication
309. Optimized hematopoietic stem cell source for the ex vivo production of mature human neutrophils as a potential cell-based therapy for neutropenia
Authors: Timmer Kyle D , Floyd Daniel , Jeffries Nathan E , Yvanovich Emma , Sykes David B , Mansour Michael 
Published: November 2023

Abstract

Background
Neutrophils or granulocytes are the most common innate immune cell and are critical for eliminating invasive pathogens. Patients with low neutrophil counts face an increased risk of fatal opportunistic infections. Allogeneic granulocyte transfusions offer a solution to supplement endogenous neutrophil counts but are challenging due to insufficient preservation methods and donation feasibility. Here, we compare the capacity of three different hematopoietic stem cell (HSC) sources; 1) cord blood (CB), 2) live adult bone marrow (LABM), and 3) cadaveric adult bone marrow (CABM), to expand and generate an ex vivo neutrophil source.

Methods
HSCs were expanded ex vivo with or without UM729 then differentiated and evaluated for neutrophil yield and purity. Ex vivo differentiated neutrophils were characterized by flow cytometry for activated phenotype surface markers. Finally, the functional capacity of ex vivo neutrophils, including phagocytosis, ectodomain shedding, and reactive oxygen species (ROS) production, was measured in response to the fungal pathogen Candida albicans.

Results
CB-derived HSCs were found to be superior in expansion capacity compared to LABM- or CABM-derived HSCs by 3-fold at day six. The use of UM729 reduced the purity of neutrophil differentiation by 44% for both live and deceased BM marrow-derived HSCs. UM729 had no observable effect on the purity of neutrophil differentiation for CB-derived HSCs. Additionally, due to enhanced Fc gamma receptor I expression, ex vivo neutrophils from all sources were ten times more sensitive to recognizing IgG-opsonized C. albicans than primary neutrophils. Ex vivo neutrophils were capable of phagocytosis, ROS production, and ectodomain shedding to a similar capacity as primary donor neutrophils.

Conclusion
We find that cadaveric bone marrow-derived HSCs are a viable source for HSC-generated neutrophils. That said, CB-derived HSC were superior in expansion capacity. We also highlight the unique opsonin-activating features of ex vivo generated neutrophils which warrant further study in granulocyte transfusion animal models of systemic infection. These data underscore the significance of neutrophil cellular therapeutics as a novel modality for preventing infection in high-risk neutropenic patients.

Disclosures
Nathan E. Jeffries, BA, Safi Biotherapeutics: Salary Michael Mansour, MD, PhD, Thermofisher: Grant/Research Support
325. Outcomes of Outpatient Parenteral Antimicrobial Therapy in the Solid Organ Transplant Population
Authors: Dillon William P , Muthanna Shadid Al , Parsons Austin , Hardy Megan , Williams Jonathan D , McCorquodale Jennifer , Ramesh Mayur , Alangaden George J 
Published: November 2023

Abstract

Background
Outpatient parenteral antimicrobial therapy (OPAT) provides an effective and convenient means to complete extended courses of antimicrobial therapy for the treatment of serious infections. There is scant data addressing OPAT related outcomes such as readmission in solid organ transplant (SOT) recipients.

Methods
In this observational cohort study, we analyzed all adult SOT recipients discharged from Henry Ford Hospital – an 877 bed quaternary care center in Detroit, Michigan - on OPAT between January 2015 and December 2020. The primary endpoint was 30-day all-cause readmission. The secondary endpoints included evaluation of risk factors associated with readmission (transplant type, reason for OPAT, OPAT related complications, length of treatment, length of stay, discharge disposition, and adequacy of infectious disease follow up and laboratory monitoring) and all-cause mortality at one year.

Results
There were 201 patients discharged on OPAT. Demographics between study populations were comparable (Table 1). A total of 83 out of 201 (41.3%) patients were readmitted. There were 38 (18.9%) patients readmitted for OPAT related complications and 45 (22.4%) for non-OPAT related reasons. Intestinal and multi-visceral transplants were associated with readmission (p=0.04 and p=0.02 respectively) while renal transplants were protective against readmission (p=0.02) (Table 1). Other factors associated with readmission include development of an OPAT related complication including treatment failure (p&lt; 0.001) (Table 2). Patients discharged without Infectious Disease follow up were less likely to be readmitted (p=0.04) (Table 3) as these patients generally had less serious infections not meriting a follow up appointment. There was no difference in mortality at one year between study populations (Table 3).

Conclusion
While the overall readmission rate of SOT discharged on OPAT is high, most readmissions were unrelated to OPAT. Patients with readmissions had higher rates of OPAT related complications and treatment failures. Further studies are warranted to optimize OPAT outcomes in the SOT population.

Disclosures
All Authors: No reported disclosures
327. Use of multiple pharmacies by people living with HIV: a qualitative analysis
Authors: Sahloff Eric G , Duggan Joan 
Published: November 2023

Abstract

Background
Multiple pharmacy use has been linked to decreased patient adherence, inappropriate drug use, adverse drug reactions, and increased mortality. Despite negative outcomes, multi-pharmacy use has increased and nearly half of all patients in the US now use multiple pharmacies. In this study, the attitudes towards multiple pharmacy use (MPU) versus single pharmacy use (SPU) for PLWH (people living with HIV) were assessed.

Methods
A convenience sample of patients in a single midwestern Ryan White clinic was surveyed. There were 24 questions with two additional questions for users of multiple pharmacies. Questions were related to patient demographics, current CD4 count (CD4), viral load (VL) status, amount of time to receive medications, missed doses, comorbidities, and patient preferences. A 5-point Likert Scale (LS; 1 = strongly disagree, 5 = strongly agree) was used to assess reasons for SPU versus MPU, including for MPU if antiretroviral medications were filled separately.

Results
142 patients participated (69 SPUs; 73 MPUs). Few differences between SPUs and MPUs for demographic indicators were identified (Table 1). SPUs were more likely to use private/commercial insurance versus government-sponsored insurance and use fewer non-HIV medications. There was no difference between groups in self-reported undetectable VL. There was a trend towards increased recall of self-reported CD4 and VL status for SPUs vs MPUs. SPUs indicated that proximity (LS weighted average (WA) = 3.64), getting all meds in one place (LS WA = 4.45), and the identification of adverse effects (LS WA = 4.17) and drug-drug interactions (LS WA = 4.06) as reasons for preferring to use a single pharmacy. For MPUs who indicated they used a separate pharmacy specifically for antiretroviral medications, the need to keep HIV status private (LS weighted average = 3.65) was noted as a significant reason.Table 1.Respondents DemographicsTable 1(cont). Respondent Demographics

Conclusion
SPUs chose a single pharmacy for reasons of convenience and safety. MPUs who chose to fill their antiretroviral therapy at a separate pharmacy stated concerns for stigma/privacy as a major contributing factor. Patient preferences should be strongly considered regarding SPU or MPU. Interestingly, MPUs were less likely to be aware of their clinical status.

Disclosures
All Authors: No reported disclosures
329. Vancomycin area under the concentration-time curve monitoring from Bayesian modeling in outpatient parenteral antimicrobial therapy
Authors: Gillett Eric M , Aleissa Muneerah M , Pearson Jeffrey C , Kubiak David W , Dionne Brandon , Chan Brian T 
Published: November 2023

Abstract

Background
Current vancomycin monitoring guidelines recommend area under the concentration-time curve to minimum inhibitory concentration (AUC/MIC) monitoring for patients with serious MRSA infections. Most AUC monitoring studies have included hospitalized patients only; however, many patients complete vancomycin therapy in the outpatient setting. While traditional two-level AUC calculations are logistically challenging for outpatients, Bayesian modeling software can allow for single level AUC estimations. There are sparse data on the feasibility, safety, and efficacy of vancomycin AUC monitoring in OPAT.

Methods
We conducted a single-center, quasi-experimental, interrupted time series study of adult patients enrolled in the OPAT program at our institution for vancomycin management. Our institution implemented a pharmacist-driven vancomycin monitoring program using AUC targets from September 8th, 2019 to February 25th, 2020, and again from September 25th, 2022 to March 16th, 2023. Patients enrolled in the monitoring program underwent vancomycin monitoring using an AUC goal of 400-600 mg*hr/L, estimated using Bayesian modeling. A cohort comprising all patients enrolled in the OPAT program from July 4th, 2021 through August 27th, 2022 for trough only vancomycin monitoring was used for comparison. Patients were excluded from analysis if they were undergoing renal replacement therapy at baseline, enrolled in OPAT for ≤ 72 hours, or did not have vancomycin levels drawn for ≥ 14 days. The primary outcome was nephrotoxicity defined as a serum creatinine increase by ≥ 0.5 mg/dL or ≥ 50% during outpatient vancomycin therapy.

Results
There were 63 patients in the AUC arm, and 60 patients in the trough-only arm. The incidence of nephrotoxicity was lower in the AUC cohort (6.3% vs 23.3%, p=0.01). There was no difference in other vancomycin-related adverse event rates (1.6% vs 10.0%, p=0.06). Vancomycin discontinuation due to adverse event was lower in the AUC arm (6.3% vs 20.0%, p=0.03).

Conclusion
Patients undergoing AUC monitoring were significantly less likely to develop nephrotoxicity during outpatient vancomycin treatment. Bayesian modeling represents a viable and safe option for vancomycin AUC monitoring in OPAT.

Disclosures
David W. Kubiak, PharmD, BCPS, BCIDP, FIDSA, Astellas Pharma, Inc.: Advisor/Consultant|AVIR Pharma Inc: Advisor/Consultant|Cidara Therapeutics: Advisor/Consultant|Shionogi Inc: Grant/Research Support